// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
package com.cloud.resource;

import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.ejb.Local;
import javax.inject.Inject;
import javax.naming.ConfigurationException;

import com.google.gson.Gson;

import org.apache.log4j.Logger;
import org.springframework.stereotype.Component;
import org.apache.cloudstack.api.ApiConstants;
import org.apache.cloudstack.api.command.admin.cluster.AddClusterCmd;
import org.apache.cloudstack.api.command.admin.cluster.DeleteClusterCmd;
import org.apache.cloudstack.api.command.admin.host.AddHostCmd;
import org.apache.cloudstack.api.command.admin.host.AddSecondaryStorageCmd;
import org.apache.cloudstack.api.command.admin.host.CancelMaintenanceCmd;
import org.apache.cloudstack.api.command.admin.host.PrepareForMaintenanceCmd;
import org.apache.cloudstack.api.command.admin.host.ReconnectHostCmd;
import org.apache.cloudstack.api.command.admin.host.UpdateHostCmd;
import org.apache.cloudstack.api.command.admin.host.UpdateHostPasswordCmd;
import org.apache.cloudstack.context.CallContext;
import org.apache.cloudstack.framework.config.dao.ConfigurationDao;
import org.apache.cloudstack.region.dao.RegionDao;
import org.apache.cloudstack.storage.datastore.db.PrimaryDataStoreDao;
import org.apache.cloudstack.storage.datastore.db.StoragePoolVO;
import org.apache.cloudstack.utils.identity.ManagementServerNode;

import com.cloud.agent.AgentManager;
import com.cloud.agent.AgentManager.TapAgentsAction;
import com.cloud.agent.api.Answer;
import com.cloud.agent.api.Command;
import com.cloud.agent.api.GetHostStatsAnswer;
import com.cloud.agent.api.GetHostStatsCommand;
import com.cloud.agent.api.MaintainAnswer;
import com.cloud.agent.api.MaintainCommand;
import com.cloud.agent.api.PropagateResourceEventCommand;
import com.cloud.agent.api.StartupCommand;
import com.cloud.agent.api.StartupRoutingCommand;
import com.cloud.agent.api.UnsupportedAnswer;
import com.cloud.agent.api.UpdateHostPasswordCommand;
import com.cloud.agent.manager.AgentAttache;
import com.cloud.agent.manager.ClusteredAgentManagerImpl;
import com.cloud.agent.manager.allocator.PodAllocator;
import com.cloud.agent.transport.Request;
import com.cloud.api.ApiDBUtils;
import com.cloud.capacity.Capacity;
import com.cloud.capacity.CapacityVO;
import com.cloud.capacity.dao.CapacityDao;
import com.cloud.cluster.ClusterManager;
import com.cloud.configuration.Config;
import com.cloud.configuration.ConfigurationManager;
import com.cloud.dc.ClusterDetailsDao;
import com.cloud.dc.ClusterDetailsVO;
import com.cloud.dc.ClusterVO;
import com.cloud.dc.DataCenter;
import com.cloud.dc.DataCenter.NetworkType;
import com.cloud.dc.DataCenterIpAddressVO;
import com.cloud.dc.DataCenterVO;
import com.cloud.dc.DedicatedResourceVO;
import com.cloud.dc.HostPodVO;
import com.cloud.dc.Pod;
import com.cloud.dc.PodCluster;
import com.cloud.dc.dao.ClusterDao;
import com.cloud.dc.dao.ClusterVSMMapDao;
import com.cloud.dc.dao.DataCenterDao;
import com.cloud.dc.dao.DataCenterIpAddressDao;
import com.cloud.dc.dao.DedicatedResourceDao;
import com.cloud.dc.dao.HostPodDao;
import com.cloud.deploy.PlannerHostReservationVO;
import com.cloud.deploy.dao.PlannerHostReservationDao;
import com.cloud.event.ActionEvent;
import com.cloud.event.EventTypes;
import com.cloud.exception.AgentUnavailableException;
import com.cloud.exception.DiscoveryException;
import com.cloud.exception.InvalidParameterValueException;
import com.cloud.exception.PermissionDeniedException;
import com.cloud.exception.ResourceInUseException;
import com.cloud.ha.HighAvailabilityManager;
import com.cloud.ha.HighAvailabilityManager.WorkType;
import com.cloud.host.DetailVO;
import com.cloud.host.Host;
import com.cloud.host.Host.Type;
import com.cloud.host.HostStats;
import com.cloud.host.HostVO;
import com.cloud.host.Status;
import com.cloud.host.Status.Event;
import com.cloud.host.dao.HostDao;
import com.cloud.host.dao.HostDetailsDao;
import com.cloud.host.dao.HostTagsDao;
import com.cloud.hypervisor.Hypervisor;
import com.cloud.hypervisor.Hypervisor.HypervisorType;
import com.cloud.hypervisor.kvm.discoverer.KvmDummyResourceBase;
import com.cloud.network.dao.IPAddressDao;
import com.cloud.network.dao.IPAddressVO;
import com.cloud.offering.ServiceOffering;
import com.cloud.org.Cluster;
import com.cloud.org.Grouping;
import com.cloud.org.Grouping.AllocationState;
import com.cloud.org.Managed;
import com.cloud.serializer.GsonHelper;
import com.cloud.storage.GuestOSCategoryVO;
import com.cloud.storage.StorageManager;
import com.cloud.storage.StoragePool;
import com.cloud.storage.StoragePoolHostVO;
import com.cloud.storage.StoragePoolStatus;
import com.cloud.storage.StorageService;
import com.cloud.storage.VMTemplateVO;
import com.cloud.storage.dao.GuestOSCategoryDao;
import com.cloud.storage.dao.StoragePoolHostDao;
import com.cloud.storage.dao.VMTemplateDao;
import com.cloud.storage.secondary.SecondaryStorageVmManager;
import com.cloud.template.VirtualMachineTemplate;
import com.cloud.user.Account;
import com.cloud.user.AccountManager;
import com.cloud.user.User;
import com.cloud.utils.Pair;
import com.cloud.utils.StringUtils;
import com.cloud.utils.UriUtils;
import com.cloud.utils.component.Manager;
import com.cloud.utils.component.ManagerBase;
import com.cloud.utils.db.DB;
import com.cloud.utils.db.GenericSearchBuilder;
import com.cloud.utils.db.GlobalLock;
import com.cloud.utils.db.SearchBuilder;
import com.cloud.utils.db.SearchCriteria;
import com.cloud.utils.db.SearchCriteria.Func;
import com.cloud.utils.db.SearchCriteria.Op;
import com.cloud.utils.db.SearchCriteria2;
import com.cloud.utils.db.SearchCriteriaService;
import com.cloud.utils.db.Transaction;
import com.cloud.utils.exception.CloudRuntimeException;
import com.cloud.utils.fsm.NoTransitionException;
import com.cloud.utils.net.Ip;
import com.cloud.utils.net.NetUtils;
import com.cloud.utils.ssh.SSHCmdHelper;
import com.cloud.utils.ssh.sshException;
import com.cloud.vm.VMInstanceVO;
import com.cloud.vm.VirtualMachine.State;
import com.cloud.vm.VirtualMachineManager;
import com.cloud.vm.dao.VMInstanceDao;

@Component
@Local({ ResourceManager.class, ResourceService.class })
public class ResourceManagerImpl extends ManagerBase implements ResourceManager, ResourceService, Manager {
    private static final Logger s_logger = Logger.getLogger(ResourceManagerImpl.class);

    Gson _gson;

    @Inject
    AccountManager _accountMgr;
    @Inject
    AgentManager _agentMgr;
    @Inject
    StorageManager _storageMgr;
    @Inject
    protected SecondaryStorageVmManager _secondaryStorageMgr;
    @Inject
    protected RegionDao _regionDao;
    @Inject
    protected DataCenterDao _dcDao;
    @Inject
    protected HostPodDao _podDao;
    @Inject
    protected ClusterDetailsDao _clusterDetailsDao;
    @Inject
    protected ClusterDao _clusterDao;
    @Inject
    protected CapacityDao _capacityDao;
    @Inject
    protected HostDao _hostDao;
    @Inject
    protected HostDetailsDao _hostDetailsDao;
    @Inject
    protected ConfigurationDao _configDao;
    @Inject
    protected HostTagsDao _hostTagsDao;
    @Inject
    protected GuestOSCategoryDao _guestOSCategoryDao;
    @Inject
    protected PrimaryDataStoreDao _storagePoolDao;
    @Inject
    protected DataCenterIpAddressDao _privateIPAddressDao;
    @Inject
    protected IPAddressDao _publicIPAddressDao;
    @Inject
    protected VirtualMachineManager _vmMgr;
    @Inject
    protected VMInstanceDao _vmDao;
    @Inject
    protected HighAvailabilityManager _haMgr;
    @Inject
    protected StorageService _storageSvr;
    @Inject
    PlannerHostReservationDao _plannerHostReserveDao;
    @Inject
    protected DedicatedResourceDao           _dedicatedDao;

    protected List<? extends Discoverer> _discoverers;

    public List<? extends Discoverer> getDiscoverers() {
        return _discoverers;
    }

    public void setDiscoverers(List<? extends Discoverer> _discoverers) {
        this._discoverers = _discoverers;
    }

    @Inject
    protected ClusterManager _clusterMgr;
    @Inject
    protected StoragePoolHostDao _storagePoolHostDao;

    protected List<PodAllocator> _podAllocators;

    public List<PodAllocator> getPodAllocators() {
        return _podAllocators;
    }

    public void setPodAllocators(List<PodAllocator> _podAllocators) {
        this._podAllocators = _podAllocators;
    }

    @Inject
    protected VMTemplateDao _templateDao;
    @Inject
    protected ConfigurationManager _configMgr;
    @Inject
    protected ClusterVSMMapDao _clusterVSMMapDao;

    protected long _nodeId = ManagementServerNode.getManagementServerId();

    protected HashMap<String, ResourceStateAdapter> _resourceStateAdapters = new HashMap<String, ResourceStateAdapter>();

    protected HashMap<Integer, List<ResourceListener>> _lifeCycleListeners = new HashMap<Integer, List<ResourceListener>>();
    private HypervisorType _defaultSystemVMHypervisor;

    private static final int ACQUIRE_GLOBAL_LOCK_TIMEOUT_FOR_COOPERATION = 30; // seconds

    private GenericSearchBuilder<HostVO, String> _hypervisorsInDC;

    private void insertListener(Integer event, ResourceListener listener) {
        List<ResourceListener> lst = _lifeCycleListeners.get(event);
        if (lst == null) {
            lst = new ArrayList<ResourceListener>();
            _lifeCycleListeners.put(event, lst);
        }

        if (lst.contains(listener)) {
            throw new CloudRuntimeException("Duplicate resource lisener:" + listener.getClass().getSimpleName());
        }

        lst.add(listener);
    }

    @Override
    public void registerResourceEvent(Integer event, ResourceListener listener) {
        synchronized (_lifeCycleListeners) {
            if ((event & ResourceListener.EVENT_DISCOVER_BEFORE) != 0) {
                insertListener(ResourceListener.EVENT_DISCOVER_BEFORE, listener);
            }
            if ((event & ResourceListener.EVENT_DISCOVER_AFTER) != 0) {
                insertListener(ResourceListener.EVENT_DISCOVER_AFTER, listener);
            }
            if ((event & ResourceListener.EVENT_DELETE_HOST_BEFORE) != 0) {
                insertListener(ResourceListener.EVENT_DELETE_HOST_BEFORE, listener);
            }
            if ((event & ResourceListener.EVENT_DELETE_HOST_AFTER) != 0) {
                insertListener(ResourceListener.EVENT_DELETE_HOST_AFTER, listener);
            }
            if ((event & ResourceListener.EVENT_CANCEL_MAINTENANCE_BEFORE) != 0) {
                insertListener(ResourceListener.EVENT_CANCEL_MAINTENANCE_BEFORE, listener);
            }
            if ((event & ResourceListener.EVENT_CANCEL_MAINTENANCE_AFTER) != 0) {
                insertListener(ResourceListener.EVENT_CANCEL_MAINTENANCE_AFTER, listener);
            }
            if ((event & ResourceListener.EVENT_PREPARE_MAINTENANCE_BEFORE) != 0) {
                insertListener(ResourceListener.EVENT_PREPARE_MAINTENANCE_BEFORE, listener);
            }
            if ((event & ResourceListener.EVENT_PREPARE_MAINTENANCE_AFTER) != 0) {
                insertListener(ResourceListener.EVENT_PREPARE_MAINTENANCE_AFTER, listener);
            }
        }
    }

    @Override
    public void unregisterResourceEvent(ResourceListener listener) {
        synchronized (_lifeCycleListeners) {
            Iterator it = _lifeCycleListeners.entrySet().iterator();
            while (it.hasNext()) {
                Map.Entry<Integer, List<ResourceListener>> items = (Map.Entry<Integer, List<ResourceListener>>) it.next();
                List<ResourceListener> lst = items.getValue();
                lst.remove(listener);
            }
        }
    }

    protected void processResourceEvent(Integer event, Object... params) {
        List<ResourceListener> lst = _lifeCycleListeners.get(event);
        if (lst == null || lst.size() == 0) {
            return;
        }

        String eventName;
        for (ResourceListener l : lst) {
            if (event == ResourceListener.EVENT_DISCOVER_BEFORE) {
                l.processDiscoverEventBefore((Long) params[0], (Long) params[1], (Long) params[2], (URI) params[3], (String) params[4],
                        (String) params[5], (List<String>) params[6]);
                eventName = "EVENT_DISCOVER_BEFORE";
            } else if (event == ResourceListener.EVENT_DISCOVER_AFTER) {
                l.processDiscoverEventAfter((Map<? extends ServerResource, Map<String, String>>) params[0]);
                eventName = "EVENT_DISCOVER_AFTER";
            } else if (event == ResourceListener.EVENT_DELETE_HOST_BEFORE) {
                l.processDeleteHostEventBefore((HostVO) params[0]);
                eventName = "EVENT_DELETE_HOST_BEFORE";
            } else if (event == ResourceListener.EVENT_DELETE_HOST_AFTER) {
                l.processDeletHostEventAfter((HostVO) params[0]);
                eventName = "EVENT_DELETE_HOST_AFTER";
            } else if (event == ResourceListener.EVENT_CANCEL_MAINTENANCE_BEFORE) {
                l.processCancelMaintenaceEventBefore((Long) params[0]);
                eventName = "EVENT_CANCEL_MAINTENANCE_BEFORE";
            } else if (event == ResourceListener.EVENT_CANCEL_MAINTENANCE_AFTER) {
                l.processCancelMaintenaceEventAfter((Long) params[0]);
                eventName = "EVENT_CANCEL_MAINTENANCE_AFTER";
            } else if (event == ResourceListener.EVENT_PREPARE_MAINTENANCE_BEFORE) {
                l.processPrepareMaintenaceEventBefore((Long) params[0]);
                eventName = "EVENT_PREPARE_MAINTENANCE_BEFORE";
            } else if (event == ResourceListener.EVENT_PREPARE_MAINTENANCE_AFTER) {
                l.processPrepareMaintenaceEventAfter((Long) params[0]);
                eventName = "EVENT_PREPARE_MAINTENANCE_AFTER";
            } else {
                throw new CloudRuntimeException("Unknown resource event:" + event);
            }
            s_logger.debug("Sent resource event " + eventName + " to listener " + l.getClass().getSimpleName());
        }

    }

    @DB
    @Override
    public List<? extends Cluster> discoverCluster(AddClusterCmd cmd) throws IllegalArgumentException, DiscoveryException, ResourceInUseException {
        long dcId = cmd.getZoneId();
        long podId = cmd.getPodId();
        String clusterName = cmd.getClusterName();
        String url = cmd.getUrl();
        String username = cmd.getUsername();
        String password = cmd.getPassword();

        if (url != null) {
            url = URLDecoder.decode(url);
        }

        URI uri = null;

        // Check if the zone exists in the system
        DataCenterVO zone = _dcDao.findById(dcId);
        if (zone == null) {
            InvalidParameterValueException ex = new InvalidParameterValueException(
                    "Can't find zone by the id specified");
            ex.addProxyObject(String.valueOf(dcId), "dcId");
            throw ex;
        }

        Account account = CallContext.current().getCallingAccount();
        if (Grouping.AllocationState.Disabled == zone.getAllocationState() && !_accountMgr.isRootAdmin(account.getType())) {
            PermissionDeniedException ex = new PermissionDeniedException(
                    "Cannot perform this operation, Zone with specified id is currently disabled");
            ex.addProxyObject(zone.getUuid(), "dcId");
            throw ex;
        }

        HostPodVO pod = _podDao.findById(podId);
        if (pod == null) {
            throw new InvalidParameterValueException("Can't find pod with specified podId " + podId);
        }

        // Check if the pod exists in the system
        if (_podDao.findById(podId) == null) {
            throw new InvalidParameterValueException("Can't find pod by id " + podId);
        }
        // check if pod belongs to the zone
        if (!Long.valueOf(pod.getDataCenterId()).equals(dcId)) {
            InvalidParameterValueException ex = new InvalidParameterValueException(
                    "Pod with specified id doesn't belong to the zone " + dcId);
            ex.addProxyObject(pod.getUuid(), "podId");
            ex.addProxyObject(zone.getUuid(), "dcId");
            throw ex;
        }

        // Verify cluster information and create a new cluster if needed
        if (clusterName == null || clusterName.isEmpty()) {
            throw new InvalidParameterValueException("Please specify cluster name");
        }

        if (cmd.getHypervisor() == null || cmd.getHypervisor().isEmpty()) {
            throw new InvalidParameterValueException("Please specify a hypervisor");
        }

        Hypervisor.HypervisorType hypervisorType = Hypervisor.HypervisorType.getType(cmd.getHypervisor());
        if (hypervisorType == null) {
            s_logger.error("Unable to resolve " + cmd.getHypervisor() + " to a valid supported hypervisor type");
            throw new InvalidParameterValueException("Unable to resolve " + cmd.getHypervisor() + " to a supported ");
        }

        if (zone.isSecurityGroupEnabled() && zone.getNetworkType().equals(NetworkType.Advanced)) {
            if (hypervisorType != HypervisorType.KVM && hypervisorType != HypervisorType.XenServer
                    && hypervisorType != HypervisorType.Simulator) {
                throw new InvalidParameterValueException("Don't support hypervisor type " + hypervisorType + " in advanced security enabled zone");
            }
        }

        Cluster.ClusterType clusterType = null;
        if (cmd.getClusterType() != null && !cmd.getClusterType().isEmpty()) {
            clusterType = Cluster.ClusterType.valueOf(cmd.getClusterType());
        }
        if (clusterType == null) {
            clusterType = Cluster.ClusterType.CloudManaged;
        }

        Grouping.AllocationState allocationState = null;
        if (cmd.getAllocationState() != null && !cmd.getAllocationState().isEmpty()) {
            try {
                allocationState = Grouping.AllocationState.valueOf(cmd.getAllocationState());
            } catch (IllegalArgumentException ex) {
                throw new InvalidParameterValueException("Unable to resolve Allocation State '" + cmd.getAllocationState() + "' to a supported state");
            }
        }
        if (allocationState == null) {
            allocationState = Grouping.AllocationState.Enabled;
        }

        Discoverer discoverer = getMatchingDiscover(hypervisorType);
        if (discoverer == null) {

            throw new InvalidParameterValueException("Could not find corresponding resource manager for " + cmd.getHypervisor());
        }

        if (hypervisorType == HypervisorType.VMware) {
            Map<String, String> allParams = cmd.getFullUrlParams();
            discoverer.putParam(allParams);
        }

        List<ClusterVO> result = new ArrayList<ClusterVO>();

        ClusterVO cluster = new ClusterVO(dcId, podId, clusterName);
        cluster.setHypervisorType(hypervisorType.toString());

        cluster.setClusterType(clusterType);
        cluster.setAllocationState(allocationState);
        try {
            cluster = _clusterDao.persist(cluster);
        } catch (Exception e) {
            // no longer tolerate exception during the cluster creation phase
            CloudRuntimeException ex = new CloudRuntimeException("Unable to create cluster " + clusterName
                    + " in pod and data center with specified ids", e);
            // Get the pod VO object's table name.
            ex.addProxyObject(pod.getUuid(), "podId");
            ex.addProxyObject(zone.getUuid(), "dcId");
            throw ex;
        }
        result.add(cluster);

        if (clusterType == Cluster.ClusterType.CloudManaged) {
            Map<String, String> details = new HashMap<String, String>();
            details.put("cpuOvercommitRatio", _configDao.getValue(Config.CPUOverprovisioningFactor.key()));
            details.put("memoryOvercommitRatio", _configDao.getValue(Config.MemOverprovisioningFactor.key()));
            _clusterDetailsDao.persist(cluster.getId(), details);
            return result;
        }

        // save cluster details for later cluster/host cross-checking
        Map<String, String> details = new HashMap<String, String>();
        details.put("url", url);
        details.put("username", username);
        details.put("password", password);
        details.put("cpuOvercommitRatio", _configDao.getValue(Config.CPUOverprovisioningFactor.key()));
        details.put("memoryOvercommitRatio", _configDao.getValue(Config.MemOverprovisioningFactor.key()));
        _clusterDetailsDao.persist(cluster.getId(), details);

        boolean success = false;
        try {
            try {
                uri = new URI(UriUtils.encodeURIComponent(url));
                if (uri.getScheme() == null) {
                    throw new InvalidParameterValueException("uri.scheme is null " + url + ", add http:// as a prefix");
                } else if (uri.getScheme().equalsIgnoreCase("http")) {
                    if (uri.getHost() == null || uri.getHost().equalsIgnoreCase("") || uri.getPath() == null || uri.getPath().equalsIgnoreCase("")) {
                        throw new InvalidParameterValueException("Your host and/or path is wrong.  Make sure it's of the format http://hostname/path");
                    }
                }
            } catch (URISyntaxException e) {
                throw new InvalidParameterValueException(url + " is not a valid uri");
            }

            List<HostVO> hosts = new ArrayList<HostVO>();
            Map<? extends ServerResource, Map<String, String>> resources = null;
            resources = discoverer.find(dcId, podId, cluster.getId(), uri, username, password, null);

            if (resources != null) {
                for (Map.Entry<? extends ServerResource, Map<String, String>> entry : resources.entrySet()) {
                    ServerResource resource = entry.getKey();

                    HostVO host = (HostVO) createHostAndAgent(resource, entry.getValue(), true, null, false);
                    if (host != null) {
                        hosts.add(host);
                    }
                    discoverer.postDiscovery(hosts, _nodeId);
                }
                s_logger.info("External cluster has been successfully discovered by " + discoverer.getName());
                success = true;
                return result;
            }

            s_logger.warn("Unable to find the server resources at " + url);
            throw new DiscoveryException("Unable to add the external cluster");
        } finally {
            if (!success) {
                _clusterDetailsDao.deleteDetails(cluster.getId());
                _clusterDao.remove(cluster.getId());
            }
        }
    }

    @Override
    public Discoverer getMatchingDiscover(Hypervisor.HypervisorType hypervisorType) {
        for (Discoverer discoverer : _discoverers) {
            if (discoverer.getHypervisorType() == hypervisorType) {
                return discoverer;
            }
        }
        return null;
    }

    @Override
    public List<? extends Host> discoverHosts(AddHostCmd cmd) throws IllegalArgumentException, DiscoveryException, InvalidParameterValueException {
        Long dcId = cmd.getZoneId();
        Long podId = cmd.getPodId();
        Long clusterId = cmd.getClusterId();
        String clusterName = cmd.getClusterName();
        String url = cmd.getUrl();
        String username = cmd.getUsername();
        String password = cmd.getPassword();
        List<String> hostTags = cmd.getHostTags();

        dcId = _accountMgr.checkAccessAndSpecifyAuthority(CallContext.current().getCallingAccount(), dcId);

        // this is for standalone option
        if (clusterName == null && clusterId == null) {
            clusterName = "Standalone-" + url;
        }

        if (clusterId != null) {
            ClusterVO cluster = _clusterDao.findById(clusterId);
            if (cluster == null) {
                InvalidParameterValueException ex = new InvalidParameterValueException(
                        "can not find cluster for specified clusterId");
                ex.addProxyObject(clusterId.toString(), "clusterId");
                throw ex;
            } else {
                if (cluster.getGuid() == null) {
                    List<HostVO> hosts = listAllHostsInCluster(clusterId);
                    if (!hosts.isEmpty()) {
                        CloudRuntimeException ex = new CloudRuntimeException(
                                "Guid is not updated for cluster with specified cluster id; need to wait for hosts in this cluster to come up");
                        ex.addProxyObject(cluster.getUuid(), "clusterId");
                        throw ex;
                    }
                }
            }
        }

        return discoverHostsFull(dcId, podId, clusterId, clusterName, url, username, password, cmd.getHypervisor(), hostTags, cmd.getFullUrlParams(),
                true);
    }

    @Override
    public List<? extends Host> discoverHosts(AddSecondaryStorageCmd cmd) throws IllegalArgumentException, DiscoveryException,
    InvalidParameterValueException {
        Long dcId = cmd.getZoneId();
        String url = cmd.getUrl();
        return discoverHostsFull(dcId, null, null, null, url, null, null, "SecondaryStorage", null, null, false);
    }

    private List<HostVO> discoverHostsFull(Long dcId, Long podId, Long clusterId, String clusterName, String url, String username, String password,
            String hypervisorType, List<String> hostTags, Map<String, String> params, boolean deferAgentCreation) throws IllegalArgumentException,
            DiscoveryException, InvalidParameterValueException {
        URI uri = null;

        // Check if the zone exists in the system
        DataCenterVO zone = _dcDao.findById(dcId);
        if (zone == null) {
            throw new InvalidParameterValueException("Can't find zone by id " + dcId);
        }

        Account account = CallContext.current().getCallingAccount();
        if (Grouping.AllocationState.Disabled == zone.getAllocationState() && !_accountMgr.isRootAdmin(account.getType())) {
            PermissionDeniedException ex = new PermissionDeniedException(
                    "Cannot perform this operation, Zone with specified id is currently disabled");
            ex.addProxyObject(zone.getUuid(), "dcId");
            throw ex;
        }

        // Check if the pod exists in the system
        if (podId != null) {
            HostPodVO pod = _podDao.findById(podId);
            if (pod == null) {
                throw new InvalidParameterValueException("Can't find pod by id " + podId);
            }
            // check if pod belongs to the zone
            if (!Long.valueOf(pod.getDataCenterId()).equals(dcId)) {
                InvalidParameterValueException ex = new InvalidParameterValueException(
                        "Pod with specified podId"
                                + podId
                                + " doesn't belong to the zone with specified zoneId"
                                + dcId);
                ex.addProxyObject(pod.getUuid(), "podId");
                ex.addProxyObject(zone.getUuid(), "dcId");
                throw ex;
            }
        }

        // Verify cluster information and create a new cluster if needed
        if (clusterName != null && clusterId != null) {
            throw new InvalidParameterValueException("Can't specify cluster by both id and name");
        }

        if (hypervisorType == null || hypervisorType.isEmpty()) {
            throw new InvalidParameterValueException("Need to specify Hypervisor Type");
        }

        if ((clusterName != null || clusterId != null) && podId == null) {
            throw new InvalidParameterValueException("Can't specify cluster without specifying the pod");
        }

        if (clusterId != null) {
            if (_clusterDao.findById(clusterId) == null) {
                throw new InvalidParameterValueException("Can't find cluster by id " + clusterId);
            }

            if (hypervisorType.equalsIgnoreCase(HypervisorType.VMware.toString())) {
                // VMware only allows adding host to an existing cluster, as we
                // already have a lot of information
                // in cluster object, to simplify user input, we will construct
                // neccessary information here
                Map<String, String> clusterDetails = _clusterDetailsDao.findDetails(clusterId);
                username = clusterDetails.get("username");
                assert (username != null);

                password = clusterDetails.get("password");
                assert (password != null);

                try {
                    uri = new URI(UriUtils.encodeURIComponent(url));

                    url = clusterDetails.get("url") + "/" + uri.getHost();
                } catch (URISyntaxException e) {
                    throw new InvalidParameterValueException(url + " is not a valid uri");
                }
            }
        }

        if (clusterName != null) {
            HostPodVO pod = _podDao.findById(podId);
            if (pod == null) {
                throw new InvalidParameterValueException("Can't find pod by id " + podId);
            }
            ClusterVO cluster = new ClusterVO(dcId, podId, clusterName);
            cluster.setHypervisorType(hypervisorType);
            try {
                cluster = _clusterDao.persist(cluster);
            } catch (Exception e) {
                cluster = _clusterDao.findBy(clusterName, podId);
                if (cluster == null) {
                    CloudRuntimeException ex = new CloudRuntimeException(
                            "Unable to create cluster "
                                    + clusterName
                                    + " in pod with specified podId and data center with specified dcID",
                                    e);
                    ex.addProxyObject(pod.getUuid(), "podId");
                    ex.addProxyObject(zone.getUuid(), "dcId");
                    throw ex;
                }
            }
            clusterId = cluster.getId();
            if (_clusterDetailsDao.findDetail(clusterId, "cpuOvercommitRatio") == null) {
                ClusterDetailsVO cluster_cpu_detail = new ClusterDetailsVO(clusterId, "cpuOvercommitRatio", "1");
                ClusterDetailsVO cluster_memory_detail = new ClusterDetailsVO(clusterId, "memoryOvercommitRatio", "1");
                _clusterDetailsDao.persist(cluster_cpu_detail);
                _clusterDetailsDao.persist(cluster_memory_detail);
            }

        }

        try {
            uri = new URI(UriUtils.encodeURIComponent(url));
            if (uri.getScheme() == null) {
                throw new InvalidParameterValueException("uri.scheme is null " + url + ", add nfs:// as a prefix");
            } else if (uri.getScheme().equalsIgnoreCase("nfs")) {
                if (uri.getHost() == null || uri.getHost().equalsIgnoreCase("") || uri.getPath() == null || uri.getPath().equalsIgnoreCase("")) {
                    throw new InvalidParameterValueException("Your host and/or path is wrong.  Make sure it's of the format nfs://hostname/path");
                }
            }
        } catch (URISyntaxException e) {
            throw new InvalidParameterValueException(url + " is not a valid uri");
        }

        List<HostVO> hosts = new ArrayList<HostVO>();
        s_logger.info("Trying to add a new host at " + url + " in data center " + dcId);
        boolean isHypervisorTypeSupported = false;
        for (Discoverer discoverer : _discoverers) {
            if (params != null) {
                discoverer.putParam(params);
            }

            if (!discoverer.matchHypervisor(hypervisorType)) {
                continue;
            }
            isHypervisorTypeSupported = true;
            Map<? extends ServerResource, Map<String, String>> resources = null;

            processResourceEvent(ResourceListener.EVENT_DISCOVER_BEFORE, dcId, podId, clusterId, uri, username, password, hostTags);
            try {
                resources = discoverer.find(dcId, podId, clusterId, uri, username, password, hostTags);
            } catch (DiscoveryException e) {
                throw e;
            } catch (Exception e) {
                s_logger.info("Exception in host discovery process with discoverer: " + discoverer.getName()
                        + ", skip to another discoverer if there is any");
            }
            processResourceEvent(ResourceListener.EVENT_DISCOVER_AFTER, resources);

            if (resources != null) {
                for (Map.Entry<? extends ServerResource, Map<String, String>> entry : resources.entrySet()) {
                    ServerResource resource = entry.getKey();
                    /*
                     * For KVM, if we go to here, that means kvm agent is
                     * already connected to mgt svr.
                     */
                    if (resource instanceof KvmDummyResourceBase) {
                        Map<String, String> details = entry.getValue();
                        String guid = details.get("guid");
                        List<HostVO> kvmHosts = listAllUpAndEnabledHosts(Host.Type.Routing, clusterId, podId, dcId);
                        for (HostVO host : kvmHosts) {
                            if (host.getGuid().equalsIgnoreCase(guid)) {
                                if (hostTags != null) {
                                    if (s_logger.isTraceEnabled()) {
                                        s_logger.trace("Adding Host Tags for KVM host, tags:  :" + hostTags);
                                    }
                                    _hostTagsDao.persist(host.getId(), hostTags);
                                }
                                hosts.add(host);
                                return hosts;
                            }
                        }
                        return null;
                    }

                    HostVO host = null;
                    if (deferAgentCreation) {
                        host = (HostVO) createHostAndAgentDeferred(resource, entry.getValue(), true, hostTags, false);
                    } else {
                        host = (HostVO) createHostAndAgent(resource, entry.getValue(), true, hostTags, false);
                    }
                    if (host != null) {
                        hosts.add(host);
                    }
                    discoverer.postDiscovery(hosts, _nodeId);

                }
                s_logger.info("server resources successfully discovered by " + discoverer.getName());
                return hosts;
            }
        }
        if (!isHypervisorTypeSupported) {
            String msg = "Do not support HypervisorType " + hypervisorType + " for " + url;
            s_logger.warn(msg);
            throw new DiscoveryException(msg);
        }
        s_logger.warn("Unable to find the server resources at " + url);
        throw new DiscoveryException("Unable to add the host");
    }

    @Override
    public Host getHost(long hostId) {
        return _hostDao.findById(hostId);
    }

    @DB
    protected boolean doDeleteHost(long hostId, boolean isForced, boolean isForceDeleteStorage) {
        User caller = _accountMgr.getActiveUser(CallContext.current().getCallingUserId());
        // Verify that host exists
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            throw new InvalidParameterValueException("Host with id " + hostId + " doesn't exist");
        }
        _accountMgr.checkAccessAndSpecifyAuthority(CallContext.current().getCallingAccount(), host.getDataCenterId());

        if (!isForced && host.getResourceState() != ResourceState.Maintenance) {
            throw new CloudRuntimeException("Host " + host.getUuid() + " cannot be deleted as it is not in maintenance mode. Either put the host into maintenance or perform a forced deletion.");
        }
        // Get storage pool host mappings here because they can be removed as a
        // part of handleDisconnect later
        // TODO: find out the bad boy, what's a buggy logic!
        List<StoragePoolHostVO> pools = _storagePoolHostDao.listByHostIdIncludingRemoved(hostId);

        ResourceStateAdapter.DeleteHostAnswer answer = (ResourceStateAdapter.DeleteHostAnswer) dispatchToStateAdapters(
                ResourceStateAdapter.Event.DELETE_HOST, false, host, new Boolean(isForced), new Boolean(isForceDeleteStorage));

        if (answer == null) {
            throw new CloudRuntimeException("No resource adapter respond to DELETE_HOST event for " + host.getName() + " id = " + hostId
                    + ", hypervisorType is " + host.getHypervisorType() + ", host type is " + host.getType());
        }

        if (answer.getIsException()) {
            return false;
        }

        if (!answer.getIsContinue()) {
            return true;
        }

        Transaction txn = Transaction.currentTxn();
        txn.start();

        _dcDao.releasePrivateIpAddress(host.getPrivateIpAddress(), host.getDataCenterId(), null);
        _agentMgr.disconnectWithoutInvestigation(hostId, Status.Event.Remove);

        // delete host details
        _hostDetailsDao.deleteDetails(hostId);

        host.setGuid(null);
        Long clusterId = host.getClusterId();
        host.setClusterId(null);
        _hostDao.update(host.getId(), host);

        _hostDao.remove(hostId);
        if (clusterId != null) {
            List<HostVO> hosts = listAllHostsInCluster(clusterId);
            if (hosts.size() == 0) {
                ClusterVO cluster = _clusterDao.findById(clusterId);
                cluster.setGuid(null);
                _clusterDao.update(clusterId, cluster);
            }
        }

        try {
            resourceStateTransitTo(host, ResourceState.Event.DeleteHost, _nodeId);
        } catch (NoTransitionException e) {
            s_logger.debug("Cannot transmit host " + host.getId() + "to Enabled state", e);
        }

        // Delete the associated entries in host ref table
        _storagePoolHostDao.deletePrimaryRecordsForHost(hostId);

        // Make sure any VMs that were marked as being on this host are cleaned up
        List<VMInstanceVO> vms = _vmDao.listByHostId(hostId);
        for (VMInstanceVO vm : vms) {
            // this is how VirtualMachineManagerImpl does it when it syncs VM states
            vm.setState(State.Stopped);
            vm.setHostId(null);
            _vmDao.persist(vm);
        }

        // For pool ids you got, delete local storage host entries in pool table
        // where
        for (StoragePoolHostVO pool : pools) {
            Long poolId = pool.getPoolId();
            StoragePoolVO storagePool = _storagePoolDao.findById(poolId);
            if (storagePool.isLocal() && isForceDeleteStorage) {
                storagePool.setUuid(null);
                storagePool.setClusterId(null);
                _storagePoolDao.update(poolId, storagePool);
                _storagePoolDao.remove(poolId);
                s_logger.debug("Local storage id=" + poolId + " is removed as a part of host removal id=" + hostId);
            }
        }

        // delete the op_host_capacity entry
        Object[] capacityTypes = { Capacity.CAPACITY_TYPE_CPU, Capacity.CAPACITY_TYPE_MEMORY };
        SearchCriteria<CapacityVO> hostCapacitySC = _capacityDao.createSearchCriteria();
        hostCapacitySC.addAnd("hostOrPoolId", SearchCriteria.Op.EQ, hostId);
        hostCapacitySC.addAnd("capacityType", SearchCriteria.Op.IN, capacityTypes);
        _capacityDao.remove(hostCapacitySC);
        // remove from dedicated resources
        DedicatedResourceVO dr = _dedicatedDao.findByHostId(hostId);
        if (dr != null) {
            _dedicatedDao.remove(dr.getId());
        }
        txn.commit();
        return true;
    }

    @Override
    public boolean deleteHost(long hostId, boolean isForced, boolean isForceDeleteStorage) {
        try {
            Boolean result = propagateResourceEvent(hostId, ResourceState.Event.DeleteHost);
            if (result != null) {
                return result;
            }
        } catch (AgentUnavailableException e) {
            return false;
        }

        return doDeleteHost(hostId, isForced, isForceDeleteStorage);
    }

    @Override
    @DB
    public boolean deleteCluster(DeleteClusterCmd cmd) {
        Transaction txn = Transaction.currentTxn();
        try {
            txn.start();
            ClusterVO cluster = _clusterDao.lockRow(cmd.getId(), true);
            if (cluster == null) {
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Cluster: " + cmd.getId() + " does not even exist.  Delete call is ignored.");
                }
                txn.rollback();
                throw new CloudRuntimeException("Cluster: " + cmd.getId() + " does not exist");
            }

            Hypervisor.HypervisorType hypervisorType = cluster.getHypervisorType();

            List<HostVO> hosts = listAllHostsInCluster(cmd.getId());
            if (hosts.size() > 0) {
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Cluster: " + cmd.getId() + " still has hosts, can't remove");
                }
                txn.rollback();
                throw new CloudRuntimeException("Cluster: " + cmd.getId() + " cannot be removed. Cluster still has hosts");
            }

            // don't allow to remove the cluster if it has non-removed storage
            // pools
            List<StoragePoolVO> storagePools = _storagePoolDao.listPoolsByCluster(cmd.getId());
            if (storagePools.size() > 0) {
                if (s_logger.isDebugEnabled()) {
                    s_logger.debug("Cluster: " + cmd.getId() + " still has storage pools, can't remove");
                }
                txn.rollback();
                throw new CloudRuntimeException("Cluster: " + cmd.getId() + " cannot be removed. Cluster still has storage pools");
            }

            if (_clusterDao.remove(cmd.getId())) {
                _capacityDao.removeBy(null, null, null, cluster.getId(), null);
                // If this cluster is of type vmware, and if the nexus vswitch
                // global parameter setting is turned
                // on, remove the row in cluster_vsm_map for this cluster id.
                if (hypervisorType == HypervisorType.VMware && Boolean.parseBoolean(_configDao.getValue(Config.VmwareUseNexusVSwitch.toString()))) {
                    _clusterVSMMapDao.removeByClusterId(cmd.getId());
                }
                // remove from dedicated resources
                DedicatedResourceVO dr = _dedicatedDao.findByClusterId(cluster.getId());
                if (dr != null) {
                    _dedicatedDao.remove(dr.getId());
                }
            }

            txn.commit();
            return true;
        } catch (CloudRuntimeException e) {
            throw e;
        } catch (Throwable t) {
            s_logger.error("Unable to delete cluster: " + cmd.getId(), t);
            txn.rollback();
            return false;
        }
    }

    @Override
    @DB
    public Cluster updateCluster(Cluster clusterToUpdate, String clusterType, String hypervisor, String allocationState, String managedstate) {

        ClusterVO cluster = (ClusterVO) clusterToUpdate;
        // Verify cluster information and update the cluster if needed
        boolean doUpdate = false;

        if (hypervisor != null && !hypervisor.isEmpty()) {
            Hypervisor.HypervisorType hypervisorType = Hypervisor.HypervisorType.getType(hypervisor);
            if (hypervisorType == null) {
                s_logger.error("Unable to resolve " + hypervisor + " to a valid supported hypervisor type");
                throw new InvalidParameterValueException("Unable to resolve " + hypervisor + " to a supported type");
            } else {
                cluster.setHypervisorType(hypervisor);
                doUpdate = true;
            }
        }

        Cluster.ClusterType newClusterType = null;
        if (clusterType != null && !clusterType.isEmpty()) {
            try {
                newClusterType = Cluster.ClusterType.valueOf(clusterType);
            } catch (IllegalArgumentException ex) {
                throw new InvalidParameterValueException("Unable to resolve " + clusterType + " to a supported type");
            }
            if (newClusterType == null) {
                s_logger.error("Unable to resolve " + clusterType + " to a valid supported cluster type");
                throw new InvalidParameterValueException("Unable to resolve " + clusterType + " to a supported type");
            } else {
                cluster.setClusterType(newClusterType);
                doUpdate = true;
            }
        }

        Grouping.AllocationState newAllocationState = null;
        if (allocationState != null && !allocationState.isEmpty()) {
            try {
                newAllocationState = Grouping.AllocationState.valueOf(allocationState);
            } catch (IllegalArgumentException ex) {
                throw new InvalidParameterValueException("Unable to resolve Allocation State '" + allocationState + "' to a supported state");
            }
            if (newAllocationState == null) {
                s_logger.error("Unable to resolve " + allocationState + " to a valid supported allocation State");
                throw new InvalidParameterValueException("Unable to resolve " + allocationState + " to a supported state");
            } else {
                _capacityDao.updateCapacityState(null, null, cluster.getId(), null, allocationState);
                cluster.setAllocationState(newAllocationState);
                doUpdate = true;
            }
        }

        Managed.ManagedState newManagedState = null;
        Managed.ManagedState oldManagedState = cluster.getManagedState();
        if (managedstate != null && !managedstate.isEmpty()) {
            try {
                newManagedState = Managed.ManagedState.valueOf(managedstate);
            } catch (IllegalArgumentException ex) {
                throw new InvalidParameterValueException("Unable to resolve Managed State '" + managedstate + "' to a supported state");
            }
            if (newManagedState == null) {
                s_logger.error("Unable to resolve Managed State '" + managedstate + "' to a supported state");
                throw new InvalidParameterValueException("Unable to resolve Managed State '" + managedstate + "' to a supported state");
            } else {
                doUpdate = true;
            }
        }

        if (doUpdate) {
            Transaction txn = Transaction.currentTxn();
            try {
                txn.start();
                _clusterDao.update(cluster.getId(), cluster);
                txn.commit();
            } catch (Exception e) {
                s_logger.error("Unable to update cluster due to " + e.getMessage(), e);
                throw new CloudRuntimeException("Failed to update cluster. Please contact Cloud Support.");
            }
        }

        if (newManagedState != null && !newManagedState.equals(oldManagedState)) {
            Transaction txn = Transaction.currentTxn();
            if (newManagedState.equals(Managed.ManagedState.Unmanaged)) {
                boolean success = false;
                try {
                    txn.start();
                    cluster.setManagedState(Managed.ManagedState.PrepareUnmanaged);
                    _clusterDao.update(cluster.getId(), cluster);
                    txn.commit();
                    List<HostVO> hosts = listAllUpAndEnabledHosts(Host.Type.Routing, cluster.getId(), cluster.getPodId(), cluster.getDataCenterId());
                    for (HostVO host : hosts) {
                        if (host.getType().equals(Host.Type.Routing) && !host.getStatus().equals(Status.Down)
                                && !host.getStatus().equals(Status.Disconnected) && !host.getStatus().equals(Status.Up)
                                && !host.getStatus().equals(Status.Alert)) {
                            String msg = "host " + host.getPrivateIpAddress() + " should not be in " + host.getStatus().toString() + " status";
                            throw new CloudRuntimeException("PrepareUnmanaged Failed due to " + msg);
                        }
                    }

                    for (HostVO host : hosts) {
                        if (host.getStatus().equals(Status.Up)) {
                            umanageHost(host.getId());
                        }
                    }
                    int retry = 40;
                    boolean lsuccess = true;
                    for (int i = 0; i < retry; i++) {
                        lsuccess = true;
                        try {
                            Thread.sleep(5 * 1000);
                        } catch (Exception e) {
                        }
                        hosts = listAllUpAndEnabledHosts(Host.Type.Routing, cluster.getId(), cluster.getPodId(), cluster.getDataCenterId());
                        for (HostVO host : hosts) {
                            if (!host.getStatus().equals(Status.Down) && !host.getStatus().equals(Status.Disconnected)
                                    && !host.getStatus().equals(Status.Alert)) {
                                lsuccess = false;
                                break;
                            }
                        }
                        if (lsuccess == true) {
                            success = true;
                            break;
                        }
                    }
                    if (success == false) {
                        throw new CloudRuntimeException(
                                "PrepareUnmanaged Failed due to some hosts are still in UP status after 5 Minutes, please try later ");
                    }
                } finally {
                    txn.start();
                    cluster.setManagedState(success ? Managed.ManagedState.Unmanaged : Managed.ManagedState.PrepareUnmanagedError);
                    _clusterDao.update(cluster.getId(), cluster);
                    txn.commit();
                }
            } else if (newManagedState.equals(Managed.ManagedState.Managed)) {
                txn.start();
                cluster.setManagedState(Managed.ManagedState.Managed);
                _clusterDao.update(cluster.getId(), cluster);
                txn.commit();
            }

        }

        return cluster;
    }

    @Override
    public Host cancelMaintenance(CancelMaintenanceCmd cmd) {
        Long hostId = cmd.getId();

        // verify input parameters
        HostVO host = _hostDao.findById(hostId);
        if (host == null || host.getRemoved() != null) {
            throw new InvalidParameterValueException("Host with id " + hostId.toString() + " doesn't exist");
        }

        processResourceEvent(ResourceListener.EVENT_CANCEL_MAINTENANCE_BEFORE, hostId);
        boolean success = cancelMaintenance(hostId);
        processResourceEvent(ResourceListener.EVENT_CANCEL_MAINTENANCE_AFTER, hostId);
        if (!success) {
            throw new CloudRuntimeException("Internal error cancelling maintenance.");
        }
        return host;
    }

    @Override
    public Host reconnectHost(ReconnectHostCmd cmd) {
        Long hostId = cmd.getId();

        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            throw new InvalidParameterValueException("Host with id " + hostId.toString() + " doesn't exist");
        }

        return (_agentMgr.reconnect(hostId) ? host : null);
    }

    @Override
    public boolean resourceStateTransitTo(Host host, ResourceState.Event event, long msId) throws NoTransitionException {
        ResourceState currentState = host.getResourceState();
        ResourceState nextState = currentState.getNextState(event);
        if (nextState == null) {
            throw new NoTransitionException("No next resource state found for current state =" + currentState + " event =" + event);
        }

        // TO DO - Make it more granular and have better conversion into
        // capacity type

        if (host.getType() == Type.Routing && host.getClusterId() != null) {
            AllocationState capacityState = _configMgr.findClusterAllocationState(ApiDBUtils.findClusterById(host.getClusterId()));
            if (capacityState == AllocationState.Enabled && nextState != ResourceState.Enabled) {
                capacityState = AllocationState.Disabled;
            }
            _capacityDao.updateCapacityState(null, null, null, host.getId(), capacityState.toString());
        }
        return _hostDao.updateResourceState(currentState, event, nextState, host);
    }

    private boolean doMaintain(final long hostId) {
        HostVO host = _hostDao.findById(hostId);
        MaintainAnswer answer = (MaintainAnswer) _agentMgr.easySend(hostId, new MaintainCommand());
        if (answer == null || !answer.getResult()) {
            s_logger.warn("Unable to send MaintainCommand to host: " + hostId);
        }

        try {
            resourceStateTransitTo(host, ResourceState.Event.AdminAskMaintenace, _nodeId);
        } catch (NoTransitionException e) {
            String err = "Cannot transimit resource state of host " + host.getId() + " to " + ResourceState.Maintenance;
            s_logger.debug(err, e);
            throw new CloudRuntimeException(err + e.getMessage());
        }

        _agentMgr.pullAgentToMaintenance(hostId);

        /* TODO: move below to listener */
        if (host.getType() == Host.Type.Routing) {

            final List<VMInstanceVO> vms = _vmDao.listByHostId(hostId);
            if (vms.size() == 0) {
                return true;
            }

            List<HostVO> hosts = listAllUpAndEnabledHosts(Host.Type.Routing, host.getClusterId(), host.getPodId(), host.getDataCenterId());
            for (final VMInstanceVO vm : vms) {
                if (hosts == null || hosts.isEmpty() || !answer.getMigrate()) {
                    // for the last host in this cluster, stop all the VMs
                    _haMgr.scheduleStop(vm, hostId, WorkType.ForceStop);
                } else {
                    _haMgr.scheduleMigration(vm);
                }
            }
        }

        return true;
    }

    @Override
    public boolean maintain(final long hostId) throws AgentUnavailableException {
        Boolean result = propagateResourceEvent(hostId, ResourceState.Event.AdminAskMaintenace);
        if (result != null) {
            return result;
        }

        return doMaintain(hostId);
    }

    @Override
    public Host maintain(PrepareForMaintenanceCmd cmd) {
        Long hostId = cmd.getId();
        HostVO host = _hostDao.findById(hostId);

        if (host == null) {
            s_logger.debug("Unable to find host " + hostId);
            throw new InvalidParameterValueException("Unable to find host with ID: " + hostId + ". Please specify a valid host ID.");
        }

        if (_hostDao.countBy(host.getClusterId(), ResourceState.PrepareForMaintenance, ResourceState.ErrorInMaintenance) > 0) {
            throw new InvalidParameterValueException("There are other servers in PrepareForMaintenance OR ErrorInMaintenance STATUS in cluster "
                    + host.getClusterId());
        }

        if (_storageMgr.isLocalStorageActiveOnHost(host.getId())) {
            throw new InvalidParameterValueException(
                    "There are active VMs using the host's local storage pool. Please stop all VMs on this host that use local storage.");
        }

        try {
            processResourceEvent(ResourceListener.EVENT_PREPARE_MAINTENANCE_BEFORE, hostId);
            if (maintain(hostId)) {
                processResourceEvent(ResourceListener.EVENT_PREPARE_MAINTENANCE_AFTER, hostId);
                return _hostDao.findById(hostId);
            } else {
                throw new CloudRuntimeException("Unable to prepare for maintenance host " + hostId);
            }
        } catch (AgentUnavailableException e) {
            throw new CloudRuntimeException("Unable to prepare for maintenance host " + hostId);
        }
    }

    @Override
    public Host updateHost(UpdateHostCmd cmd) throws NoTransitionException {
        Long hostId = cmd.getId();
        Long guestOSCategoryId = cmd.getOsCategoryId();

        // Verify that the host exists
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            throw new InvalidParameterValueException("Host with id " + hostId + " doesn't exist");
        }

        if (cmd.getAllocationState() != null) {
            ResourceState.Event resourceEvent = ResourceState.Event.toEvent(cmd.getAllocationState());
            if (resourceEvent != ResourceState.Event.Enable && resourceEvent != ResourceState.Event.Disable) {
                throw new CloudRuntimeException("Invalid allocation state:" + cmd.getAllocationState() + ", only Enable/Disable are allowed");
            }

            resourceStateTransitTo(host, resourceEvent, _nodeId);
        }

        if (guestOSCategoryId != null) {
            // Verify that the guest OS Category exists
            if (guestOSCategoryId > 0) {
                if (_guestOSCategoryDao.findById(guestOSCategoryId) == null) {
                    throw new InvalidParameterValueException("Please specify a valid guest OS category.");
                }
            }

            GuestOSCategoryVO guestOSCategory = _guestOSCategoryDao.findById(guestOSCategoryId);
            Map<String, String> hostDetails = _hostDetailsDao.findDetails(hostId);

            if (guestOSCategory != null && !GuestOSCategoryVO.CATEGORY_NONE.equalsIgnoreCase(guestOSCategory.getName())) {
                // Save a new entry for guest.os.category.id
                hostDetails.put("guest.os.category.id", String.valueOf(guestOSCategory.getId()));
            } else {
                // Delete any existing entry for guest.os.category.id
                hostDetails.remove("guest.os.category.id");
            }
            _hostDetailsDao.persist(hostId, hostDetails);
        }

        List<String> hostTags = cmd.getHostTags();
        if (hostTags != null) {
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Updating Host Tags to :" + hostTags);
            }
            _hostTagsDao.persist(hostId, hostTags);
        }

        String url = cmd.getUrl();
        if (url != null) {
            _storageMgr.updateSecondaryStorage(cmd.getId(), cmd.getUrl());
        }

        HostVO updatedHost = _hostDao.findById(hostId);
        return updatedHost;
    }

    @Override
    public Cluster getCluster(Long clusterId) {
        return _clusterDao.findById(clusterId);
    }

    @Override
    public boolean configure(String name, Map<String, Object> params) throws ConfigurationException {
        _defaultSystemVMHypervisor = HypervisorType.getType(_configDao.getValue(Config.SystemVMDefaultHypervisor.toString()));
        _gson = GsonHelper.getGson();

        _hypervisorsInDC = _hostDao.createSearchBuilder(String.class);
        _hypervisorsInDC.select(null, Func.DISTINCT, _hypervisorsInDC.entity().getHypervisorType());
        _hypervisorsInDC.and("hypervisorType", _hypervisorsInDC.entity().getHypervisorType(), SearchCriteria.Op.NNULL);
        _hypervisorsInDC.and("dataCenter", _hypervisorsInDC.entity().getDataCenterId(), SearchCriteria.Op.EQ);
        _hypervisorsInDC.and("id", _hypervisorsInDC.entity().getId(), SearchCriteria.Op.NEQ);
        _hypervisorsInDC.and("type", _hypervisorsInDC.entity().getType(), SearchCriteria.Op.EQ);
        _hypervisorsInDC.done();

        return true;
    }

    @Override
    public List<HypervisorType> getSupportedHypervisorTypes(long zoneId, boolean forVirtualRouter, Long podId) {
        List<HypervisorType> hypervisorTypes = new ArrayList<HypervisorType>();

        List<ClusterVO> clustersForZone = new ArrayList<ClusterVO>();
        if (podId != null) {
            clustersForZone = _clusterDao.listByPodId(podId);
        } else {
            clustersForZone = _clusterDao.listByZoneId(zoneId);
        }

        for (ClusterVO cluster : clustersForZone) {
            HypervisorType hType = cluster.getHypervisorType();
            if (!forVirtualRouter || (forVirtualRouter && hType != HypervisorType.BareMetal && hType != HypervisorType.Ovm)) {
                hypervisorTypes.add(hType);
            }
        }

        return hypervisorTypes;
    }

    @Override
    public HypervisorType getDefaultHypervisor(long zoneId) {
        HypervisorType defaultHyper = HypervisorType.None;
        if (_defaultSystemVMHypervisor != HypervisorType.None) {
            defaultHyper = _defaultSystemVMHypervisor;
        }

        DataCenterVO dc = _dcDao.findById(zoneId);
        if (dc == null) {
            return HypervisorType.None;
        }
        _dcDao.loadDetails(dc);
        String defaultHypervisorInZone = dc.getDetail("defaultSystemVMHypervisorType");
        if (defaultHypervisorInZone != null) {
            defaultHyper = HypervisorType.getType(defaultHypervisorInZone);
        }

        List<VMTemplateVO> systemTemplates = _templateDao.listAllSystemVMTemplates();
        boolean isValid = false;
        for (VMTemplateVO template : systemTemplates) {
            if (template.getHypervisorType() == defaultHyper) {
                isValid = true;
                break;
            }
        }

        if (isValid) {
            List<ClusterVO> clusters = _clusterDao.listByDcHyType(zoneId, defaultHyper.toString());
            if (clusters.size() <= 0) {
                isValid = false;
            }
        }

        if (isValid) {
            return defaultHyper;
        } else {
            return HypervisorType.None;
        }
    }

    @Override
    public HypervisorType getAvailableHypervisor(long zoneId) {
        HypervisorType defaultHype = getDefaultHypervisor(zoneId);
        if (defaultHype == HypervisorType.None) {
            List<HypervisorType> supportedHypes = getSupportedHypervisorTypes(zoneId, false, null);
            if (supportedHypes.size() > 0) {
                Collections.shuffle(supportedHypes);
                defaultHype = supportedHypes.get(0);
            }
        }

        if (defaultHype == HypervisorType.None) {
            defaultHype = HypervisorType.Any;
        }
        return defaultHype;
    }

    @Override
    public void registerResourceStateAdapter(String name, ResourceStateAdapter adapter) {
        if (_resourceStateAdapters.get(name) != null) {
            throw new CloudRuntimeException(name + " has registered");
        }

        synchronized (_resourceStateAdapters) {
            _resourceStateAdapters.put(name, adapter);
        }
    }

    @Override
    public void unregisterResourceStateAdapter(String name) {
        synchronized (_resourceStateAdapters) {
            _resourceStateAdapters.remove(name);
        }
    }

    private Object dispatchToStateAdapters(ResourceStateAdapter.Event event, boolean singleTaker, Object... args) {
        synchronized (_resourceStateAdapters) {
            Iterator<Map.Entry<String, ResourceStateAdapter>> it = _resourceStateAdapters.entrySet().iterator();
            Object result = null;
            while (it.hasNext()) {
                Map.Entry<String, ResourceStateAdapter> item = it
                        .next();
                ResourceStateAdapter adapter = item.getValue();

                String msg = new String("Dispatching resource state event " + event + " to " + item.getKey());
                s_logger.debug(msg);

                if (event == ResourceStateAdapter.Event.CREATE_HOST_VO_FOR_CONNECTED) {
                    result = adapter.createHostVOForConnectedAgent((HostVO) args[0], (StartupCommand[]) args[1]);
                    if (result != null && singleTaker) {
                        break;
                    }
                } else if (event == ResourceStateAdapter.Event.CREATE_HOST_VO_FOR_DIRECT_CONNECT) {
                    result = adapter.createHostVOForDirectConnectAgent((HostVO) args[0], (StartupCommand[]) args[1], (ServerResource) args[2],
                            (Map<String, String>) args[3], (List<String>) args[4]);
                    if (result != null && singleTaker) {
                        break;
                    }
                } else if (event == ResourceStateAdapter.Event.DELETE_HOST) {
                    try {
                        result = adapter.deleteHost((HostVO) args[0], (Boolean) args[1], (Boolean) args[2]);
                        if (result != null) {
                            break;
                        }
                    } catch (UnableDeleteHostException e) {
                        s_logger.debug("Adapter " + adapter.getName() + " says unable to delete host", e);
                        result = new ResourceStateAdapter.DeleteHostAnswer(false, true);
                    }
                } else {
                    throw new CloudRuntimeException("Unknown resource state event:" + event);
                }
            }

            return result;
        }
    }

    @Override
    public void checkCIDR(HostPodVO pod, DataCenterVO dc, String serverPrivateIP, String serverPrivateNetmask) throws IllegalArgumentException {
        if (serverPrivateIP == null) {
            return;
        }
        // Get the CIDR address and CIDR size
        String cidrAddress = pod.getCidrAddress();
        long cidrSize = pod.getCidrSize();

        // If the server's private IP address is not in the same subnet as the
        // pod's CIDR, return false
        String cidrSubnet = NetUtils.getCidrSubNet(cidrAddress, cidrSize);
        String serverSubnet = NetUtils.getSubNet(serverPrivateIP, serverPrivateNetmask);
        if (!cidrSubnet.equals(serverSubnet)) {
            s_logger.warn("The private ip address of the server (" + serverPrivateIP + ") is not compatible with the CIDR of pod: " + pod.getName()
                    + " and zone: " + dc.getName());
            throw new IllegalArgumentException("The private ip address of the server (" + serverPrivateIP
                    + ") is not compatible with the CIDR of pod: " + pod.getName() + " and zone: " + dc.getName());
        }

        // If the server's private netmask is less inclusive than the pod's CIDR
        // netmask, return false
        String cidrNetmask = NetUtils.getCidrSubNet("255.255.255.255", cidrSize);
        long cidrNetmaskNumeric = NetUtils.ip2Long(cidrNetmask);
        long serverNetmaskNumeric = NetUtils.ip2Long(serverPrivateNetmask);
        if (serverNetmaskNumeric > cidrNetmaskNumeric) {
            throw new IllegalArgumentException("The private ip address of the server (" + serverPrivateIP
                    + ") is not compatible with the CIDR of pod: " + pod.getName() + " and zone: " + dc.getName());
        }

    }

    private boolean checkCIDR(HostPodVO pod, String serverPrivateIP, String serverPrivateNetmask) {
        if (serverPrivateIP == null) {
            return true;
        }
        // Get the CIDR address and CIDR size
        String cidrAddress = pod.getCidrAddress();
        long cidrSize = pod.getCidrSize();

        // If the server's private IP address is not in the same subnet as the
        // pod's CIDR, return false
        String cidrSubnet = NetUtils.getCidrSubNet(cidrAddress, cidrSize);
        String serverSubnet = NetUtils.getSubNet(serverPrivateIP, serverPrivateNetmask);
        if (!cidrSubnet.equals(serverSubnet)) {
            return false;
        }

        // If the server's private netmask is less inclusive than the pod's CIDR
        // netmask, return false
        String cidrNetmask = NetUtils.getCidrSubNet("255.255.255.255", cidrSize);
        long cidrNetmaskNumeric = NetUtils.ip2Long(cidrNetmask);
        long serverNetmaskNumeric = NetUtils.ip2Long(serverPrivateNetmask);
        if (serverNetmaskNumeric > cidrNetmaskNumeric) {
            return false;
        }
        return true;
    }

    protected HostVO createHostVO(StartupCommand[] cmds, ServerResource resource, Map<String, String> details, List<String> hostTags,
            ResourceStateAdapter.Event stateEvent) {
        StartupCommand startup = cmds[0];
        HostVO host = findHostByGuid(startup.getGuid());
        boolean isNew = false;
        if (host == null) {
            host = findHostByGuid(startup.getGuidWithoutResource());
        }
        if (host == null) {
            host = new HostVO(startup.getGuid());
            isNew = true;
        }

        String dataCenter = startup.getDataCenter();
        String pod = startup.getPod();
        String cluster = startup.getCluster();

        if (pod != null && dataCenter != null && pod.equalsIgnoreCase("default") && dataCenter.equalsIgnoreCase("default")) {
            List<HostPodVO> pods = _podDao.listAllIncludingRemoved();
            for (HostPodVO hpv : pods) {
                if (checkCIDR(hpv, startup.getPrivateIpAddress(), startup.getPrivateNetmask())) {
                    pod = hpv.getName();
                    dataCenter = _dcDao.findById(hpv.getDataCenterId()).getName();
                    break;
                }
            }
        }

        long dcId = -1;
        DataCenterVO dc = _dcDao.findByName(dataCenter);
        if (dc == null) {
            try {
                dcId = Long.parseLong(dataCenter);
                dc = _dcDao.findById(dcId);
            } catch (final NumberFormatException e) {
            }
        }
        if (dc == null) {
            throw new IllegalArgumentException("Host " + startup.getPrivateIpAddress() + " sent incorrect data center: " + dataCenter);
        }
        dcId = dc.getId();

        HostPodVO p = _podDao.findByName(pod, dcId);
        if (p == null) {
            try {
                final long podId = Long.parseLong(pod);
                p = _podDao.findById(podId);
            } catch (final NumberFormatException e) {
            }
        }
        /*
         * ResourceStateAdapter is responsible for throwing Exception if Pod is
         * null and non-null is required. for example, XcpServerDiscoever.
         * Others, like PxeServer, ExternalFireware don't require Pod
         */
        Long podId = (p == null ? null : p.getId());

        Long clusterId = null;
        if (cluster != null) {
            try {
                clusterId = Long.valueOf(cluster);
            } catch (NumberFormatException e) {
                ClusterVO c = _clusterDao.findBy(cluster, podId);
                if (c == null) {
                    c = new ClusterVO(dcId, podId, cluster);
                    c = _clusterDao.persist(c);
                }
                clusterId = c.getId();
            }
        }

        host.setDataCenterId(dc.getId());
        host.setPodId(podId);
        host.setClusterId(clusterId);
        host.setPrivateIpAddress(startup.getPrivateIpAddress());
        host.setPrivateNetmask(startup.getPrivateNetmask());
        host.setPrivateMacAddress(startup.getPrivateMacAddress());
        host.setPublicIpAddress(startup.getPublicIpAddress());
        host.setPublicMacAddress(startup.getPublicMacAddress());
        host.setPublicNetmask(startup.getPublicNetmask());
        host.setStorageIpAddress(startup.getStorageIpAddress());
        host.setStorageMacAddress(startup.getStorageMacAddress());
        host.setStorageNetmask(startup.getStorageNetmask());
        host.setVersion(startup.getVersion());
        host.setName(startup.getName());
        host.setManagementServerId(_nodeId);
        host.setStorageUrl(startup.getIqn());
        host.setLastPinged(System.currentTimeMillis() >> 10);
        host.setHostTags(hostTags);
        host.setDetails(details);
        if (startup.getStorageIpAddressDeux() != null) {
            host.setStorageIpAddressDeux(startup.getStorageIpAddressDeux());
            host.setStorageMacAddressDeux(startup.getStorageMacAddressDeux());
            host.setStorageNetmaskDeux(startup.getStorageNetmaskDeux());
        }
        if (resource != null) {
            /* null when agent is connected agent */
            host.setResource(resource.getClass().getName());
        }

        host = (HostVO) dispatchToStateAdapters(stateEvent, true, host, cmds, resource, details, hostTags);
        if (host == null) {
            throw new CloudRuntimeException("No resource state adapter response");
        }

        if (isNew) {
            host = _hostDao.persist(host);
        } else {
            _hostDao.update(host.getId(), host);
        }

        try {
            resourceStateTransitTo(host, ResourceState.Event.InternalCreated, _nodeId);
            /* Agent goes to Connecting status */
            _agentMgr.agentStatusTransitTo(host, Status.Event.AgentConnected, _nodeId);
        } catch (Exception e) {
            s_logger.debug("Cannot transmit host " + host.getId() + " to Creating state", e);
            _agentMgr.agentStatusTransitTo(host, Status.Event.Error, _nodeId);
            try {
                resourceStateTransitTo(host, ResourceState.Event.Error, _nodeId);
            } catch (NoTransitionException e1) {
                s_logger.debug("Cannot transmit host " + host.getId() + "to Error state", e);
            }
        }

        return host;
    }

    private boolean isFirstHostInCluster(HostVO host) {
        boolean isFirstHost = true;
        if (host.getClusterId() != null) {
            SearchBuilder<HostVO> sb = _hostDao.createSearchBuilder();
            sb.and("removed", sb.entity().getRemoved(), SearchCriteria.Op.NULL);
            sb.and("cluster", sb.entity().getClusterId(), SearchCriteria.Op.EQ);
            sb.done();
            SearchCriteria<HostVO> sc = sb.create();
            sc.setParameters("cluster", host.getClusterId());

            List<HostVO> hosts = _hostDao.search(sc, null);
            if (hosts != null && hosts.size() > 1) {
                isFirstHost = false;
            }
        }
        return isFirstHost;
    }

    private void markHostAsDisconnected(HostVO host, StartupCommand[] cmds) {
        if (host == null) { // in case host is null due to some errors, try
            // reloading the host from db
            if (cmds != null) {
                StartupCommand firstCmd = cmds[0];
                host = findHostByGuid(firstCmd.getGuid());
                if (host == null) {
                    host = findHostByGuid(firstCmd.getGuidWithoutResource());
                }
            }
        }

        if (host != null) {
            // Change agent status to Alert, so that host is considered for
            // reconnection next time
            _agentMgr.agentStatusTransitTo(host, Status.Event.AgentDisconnected, _nodeId);
        }
    }

    private Host createHostAndAgent(ServerResource resource, Map<String, String> details, boolean old, List<String> hostTags, boolean forRebalance) {
        HostVO host = null;
        AgentAttache attache = null;
        StartupCommand[] cmds = null;
        boolean hostExists = false;

        try {
            cmds = resource.initialize();
            if (cmds == null) {
                s_logger.info("Unable to fully initialize the agent because no StartupCommands are returned");
                return null;
            }

            /* Generate a random version in a dev setup situation */
            if (this.getClass().getPackage().getImplementationVersion() == null) {
                for (StartupCommand cmd : cmds) {
                    if (cmd.getVersion() == null) {
                        cmd.setVersion(Long.toString(System.currentTimeMillis()));
                    }
                }
            }

            if (s_logger.isDebugEnabled()) {
                new Request(-1l, -1l, cmds, true, false).logD("Startup request from directly connected host: ", true);
            }

            if (old) {
                StartupCommand firstCmd = cmds[0];
                host = findHostByGuid(firstCmd.getGuid());
                if (host == null) {
                    host = findHostByGuid(firstCmd.getGuidWithoutResource());
                }
                if (host != null && host.getRemoved() == null) { // host already
                    // added, no
                    // need to add
                    // again
                    s_logger.debug("Found the host " + host.getId() + " by guid: " + firstCmd.getGuid() + ", old host reconnected as new");
                    hostExists = true; // ensures that host status is left
                    // unchanged in case of adding same one
                    // again
                    return null;
                }
            }

            host = createHostVO(cmds, resource, details, hostTags, ResourceStateAdapter.Event.CREATE_HOST_VO_FOR_DIRECT_CONNECT);
            if (host != null) {
                attache = _agentMgr.handleDirectConnectAgent(host, cmds, resource, forRebalance);
                /* reload myself from database */
                host = _hostDao.findById(host.getId());
            }
        } catch (Exception e) {
            s_logger.warn("Unable to connect due to ", e);
        } finally {
            if (hostExists) {
                if (cmds != null) {
                    resource.disconnected();
                }
            } else {
                if (attache == null) {
                    if (cmds != null) {
                        resource.disconnected();
                    }
                    markHostAsDisconnected(host, cmds);
                }
            }
        }

        return host;
    }

    private Host createHostAndAgentDeferred(ServerResource resource, Map<String, String> details, boolean old, List<String> hostTags,
            boolean forRebalance) {
        HostVO host = null;
        AgentAttache attache = null;
        StartupCommand[] cmds = null;
        boolean hostExists = false;
        boolean deferAgentCreation = true;

        try {
            cmds = resource.initialize();
            if (cmds == null) {
                s_logger.info("Unable to fully initialize the agent because no StartupCommands are returned");
                return null;
            }

            /* Generate a random version in a dev setup situation */
            if (this.getClass().getPackage().getImplementationVersion() == null) {
                for (StartupCommand cmd : cmds) {
                    if (cmd.getVersion() == null) {
                        cmd.setVersion(Long.toString(System.currentTimeMillis()));
                    }
                }
            }

            if (s_logger.isDebugEnabled()) {
                new Request(-1l, -1l, cmds, true, false).logD("Startup request from directly connected host: ", true);
            }

            if (old) {
                StartupCommand firstCmd = cmds[0];
                host = findHostByGuid(firstCmd.getGuid());
                if (host == null) {
                    host = findHostByGuid(firstCmd.getGuidWithoutResource());
                }
                if (host != null && host.getRemoved() == null) { // host already
                    // added, no
                    // need to add
                    // again
                    s_logger.debug("Found the host " + host.getId() + " by guid: " + firstCmd.getGuid() + ", old host reconnected as new");
                    hostExists = true; // ensures that host status is left
                    // unchanged in case of adding same one
                    // again
                    return null;
                }
            }

            host = null;
            GlobalLock addHostLock = GlobalLock.getInternLock("AddHostLock");
            try {
                if (addHostLock.lock(ACQUIRE_GLOBAL_LOCK_TIMEOUT_FOR_COOPERATION)) { // to
                    // safely
                    // determine
                    // first
                    // host
                    // in
                    // cluster
                    // in
                    // multi-MS
                    // scenario
                    try {
                        host = createHostVO(cmds, resource, details, hostTags, ResourceStateAdapter.Event.CREATE_HOST_VO_FOR_DIRECT_CONNECT);
                        if (host != null) {
                            deferAgentCreation = !isFirstHostInCluster(host); // if
                            // first
                            // host
                            // in
                            // cluster
                            // no
                            // need
                            // to
                            // defer
                            // agent
                            // creation
                        }
                    } finally {
                        addHostLock.unlock();
                    }
                }
            } finally {
                addHostLock.releaseRef();
            }

            if (host != null) {
                if (!deferAgentCreation) { // if first host in cluster then
                    // create agent otherwise defer it to
                    // scan task
                    attache = _agentMgr.handleDirectConnectAgent(host, cmds, resource, forRebalance);
                    host = _hostDao.findById(host.getId()); // reload
                } else {
                    host = _hostDao.findById(host.getId()); // reload
                    // force host status to 'Alert' so that it is loaded for
                    // connection during next scan task
                    _agentMgr.agentStatusTransitTo(host, Status.Event.AgentDisconnected, _nodeId);

                    host = _hostDao.findById(host.getId()); // reload
                    host.setLastPinged(0); // so that scan task can pick it up
                    _hostDao.update(host.getId(), host);

                    // schedule a scan task immediately
                    if (_agentMgr instanceof ClusteredAgentManagerImpl) {
                        ClusteredAgentManagerImpl clusteredAgentMgr = (ClusteredAgentManagerImpl) _agentMgr;
                        if (s_logger.isDebugEnabled()) {
                            s_logger.debug("Scheduling a host scan task");
                        }
                        // schedule host scan task on current MS
                        clusteredAgentMgr.scheduleHostScanTask();
                        if (s_logger.isDebugEnabled()) {
                            s_logger.debug("Notifying all peer MS to schedule host scan task");
                        }
                        // notify peers to schedule a host scan task as well
                        clusteredAgentMgr.notifyNodesInClusterToScheduleHostScanTask();
                    }
                }
            }
        } catch (Exception e) {
            s_logger.warn("Unable to connect due to ", e);
        } finally {
            if (hostExists) {
                if (cmds != null) {
                    resource.disconnected();
                }
            } else {
                if (!deferAgentCreation && attache == null) {
                    if (cmds != null) {
                        resource.disconnected();
                    }
                    markHostAsDisconnected(host, cmds);
                }
            }
        }

        return host;
    }

    @Override
    public Host createHostAndAgent(Long hostId, ServerResource resource, Map<String, String> details, boolean old, List<String> hostTags,
            boolean forRebalance) {
        _agentMgr.tapLoadingAgents(hostId, TapAgentsAction.Add);
        Host host = createHostAndAgent(resource, details, old, hostTags, forRebalance);
        _agentMgr.tapLoadingAgents(hostId, TapAgentsAction.Del);
        return host;
    }

    @Override
    public Host addHost(long zoneId, ServerResource resource, Type hostType, Map<String, String> hostDetails) {
        // Check if the zone exists in the system
        if (_dcDao.findById(zoneId) == null) {
            throw new InvalidParameterValueException("Can't find zone with id " + zoneId);
        }

        Map<String, String> details = hostDetails;
        String guid = details.get("guid");
        List<HostVO> currentHosts = listAllUpAndEnabledHostsInOneZoneByType(hostType, zoneId);
        for (HostVO currentHost : currentHosts) {
            if (currentHost.getGuid().equals(guid)) {
                return currentHost;
            }
        }

        return createHostAndAgent(resource, hostDetails, true, null, false);
    }

    @Override
    public HostVO createHostVOForConnectedAgent(StartupCommand[] cmds) {
        return createHostVO(cmds, null, null, null, ResourceStateAdapter.Event.CREATE_HOST_VO_FOR_CONNECTED);
    }

    private void checkIPConflicts(HostPodVO pod, DataCenterVO dc, String serverPrivateIP, String serverPrivateNetmask, String serverPublicIP,
            String serverPublicNetmask) {
        // If the server's private IP is the same as is public IP, this host has
        // a host-only private network. Don't check for conflicts with the
        // private IP address table.
        if (serverPrivateIP != serverPublicIP) {
            if (!_privateIPAddressDao.mark(dc.getId(), pod.getId(), serverPrivateIP)) {
                // If the server's private IP address is already in the
                // database, return false
                List<DataCenterIpAddressVO> existingPrivateIPs = _privateIPAddressDao.listByPodIdDcIdIpAddress(pod.getId(), dc.getId(),
                        serverPrivateIP);

                assert existingPrivateIPs.size() <= 1 : " How can we get more than one ip address with " + serverPrivateIP;
                if (existingPrivateIPs.size() > 1) {
                    throw new IllegalArgumentException("The private ip address of the server (" + serverPrivateIP + ") is already in use in pod: "
                            + pod.getName() + " and zone: " + dc.getName());
                }
                if (existingPrivateIPs.size() == 1) {
                    DataCenterIpAddressVO vo = existingPrivateIPs.get(0);
                    if (vo.getInstanceId() != null) {
                        throw new IllegalArgumentException("The private ip address of the server (" + serverPrivateIP
                                + ") is already in use in pod: " + pod.getName() + " and zone: " + dc.getName());
                    }
                }
            }
        }

        if (serverPublicIP != null && !_publicIPAddressDao.mark(dc.getId(), new Ip(serverPublicIP))) {
            // If the server's public IP address is already in the database,
            // return false
            List<IPAddressVO> existingPublicIPs = _publicIPAddressDao.listByDcIdIpAddress(dc.getId(), serverPublicIP);
            if (existingPublicIPs.size() > 0) {
                throw new IllegalArgumentException("The public ip address of the server (" + serverPublicIP + ") is already in use in zone: "
                        + dc.getName());
            }
        }
    }

    @Override
    public HostVO fillRoutingHostVO(HostVO host, StartupRoutingCommand ssCmd, HypervisorType hyType, Map<String, String> details,
            List<String> hostTags) {
        if (host.getPodId() == null) {
            s_logger.error("Host " + ssCmd.getPrivateIpAddress() + " sent incorrect pod, pod id is null");
            throw new IllegalArgumentException("Host " + ssCmd.getPrivateIpAddress() + " sent incorrect pod, pod id is null");
        }

        ClusterVO clusterVO = _clusterDao.findById(host.getClusterId());
        if (clusterVO.getHypervisorType() != hyType) {
            throw new IllegalArgumentException("Can't add host whose hypervisor type is: " + hyType + " into cluster: " + clusterVO.getId()
                    + " whose hypervisor type is: " + clusterVO.getHypervisorType());
        }

        final Map<String, String> hostDetails = ssCmd.getHostDetails();
        if (hostDetails != null) {
            if (details != null) {
                details.putAll(hostDetails);
            } else {
                details = hostDetails;
            }
        }

        HostPodVO pod = _podDao.findById(host.getPodId());
        DataCenterVO dc = _dcDao.findById(host.getDataCenterId());
        checkIPConflicts(pod, dc, ssCmd.getPrivateIpAddress(), ssCmd.getPublicIpAddress(), ssCmd.getPublicIpAddress(), ssCmd.getPublicNetmask());
        host.setType(com.cloud.host.Host.Type.Routing);
        host.setDetails(details);
        host.setCaps(ssCmd.getCapabilities());
        host.setCpus(ssCmd.getCpus());
        host.setTotalMemory(ssCmd.getMemory());
        host.setSpeed(ssCmd.getSpeed());
        host.setHypervisorType(hyType);
        host.setHypervisorVersion(ssCmd.getHypervisorVersion());
        return host;
    }

    @Override
    public void deleteRoutingHost(HostVO host, boolean isForced, boolean forceDestroyStorage) throws UnableDeleteHostException {
        if (host.getType() != Host.Type.Routing) {
            throw new CloudRuntimeException("Non-Routing host gets in deleteRoutingHost, id is " + host.getId());
        }

        if (s_logger.isDebugEnabled()) {
            s_logger.debug("Deleting Host: " + host.getId() + " Guid:" + host.getGuid());
        }

        if (forceDestroyStorage) {
            // put local storage into mainenance mode, will set all the VMs on
            // this local storage into stopped state
            StoragePoolVO storagePool = _storageMgr.findLocalStorageOnHost(host.getId());
            if (storagePool != null) {
                if (storagePool.getStatus() == StoragePoolStatus.Up || storagePool.getStatus() == StoragePoolStatus.ErrorInMaintenance) {
                    try {
                        StoragePool pool = _storageSvr.preparePrimaryStorageForMaintenance(storagePool.getId());
                        if (pool == null) {
                            s_logger.debug("Failed to set primary storage into maintenance mode");

                            throw new UnableDeleteHostException("Failed to set primary storage into maintenance mode");
                        }
                    } catch (Exception e) {
                        s_logger.debug("Failed to set primary storage into maintenance mode, due to: " + e.toString());
                        throw new UnableDeleteHostException("Failed to set primary storage into maintenance mode, due to: " + e.toString());
                    }
                }

                List<VMInstanceVO> vmsOnLocalStorage = _storageMgr.listByStoragePool(storagePool.getId());
                for (VMInstanceVO vm : vmsOnLocalStorage) {
                    try {
                        _vmMgr.destroy(vm.getUuid());
                    } catch (Exception e) {
                        String errorMsg = "There was an error Destory the vm: " + vm + " as a part of hostDelete id=" + host.getId();
                        s_logger.debug(errorMsg, e);
                        throw new UnableDeleteHostException(errorMsg + "," + e.getMessage());
                    }
                }
            }
        } else {
            // Check if there are vms running/starting/stopping on this host
            List<VMInstanceVO> vms = _vmDao.listByHostId(host.getId());
            if (!vms.isEmpty()) {
                if (isForced) {
                    // Stop HA disabled vms and HA enabled vms in Stopping state
                    // Restart HA enabled vms
                    for (VMInstanceVO vm : vms) {
                        if (!vm.isHaEnabled() || vm.getState() == State.Stopping) {
                            s_logger.debug("Stopping vm: " + vm + " as a part of deleteHost id=" + host.getId());
                            try {
                                _vmMgr.advanceStop(vm.getUuid(), false);
                            } catch (Exception e) {
                                String errorMsg = "There was an error stopping the vm: " + vm + " as a part of hostDelete id=" + host.getId();
                                s_logger.debug(errorMsg, e);
                                throw new UnableDeleteHostException(errorMsg + "," + e.getMessage());
                            }
                        } else if (vm.isHaEnabled() && (vm.getState() == State.Running || vm.getState() == State.Starting)) {
                            s_logger.debug("Scheduling restart for vm: " + vm + " " + vm.getState() + " on the host id=" + host.getId());
                            _haMgr.scheduleRestart(vm, false);
                        }
                    }
                } else {
                    throw new UnableDeleteHostException("Unable to delete the host as there are vms in " + vms.get(0).getState()
                            + " state using this host and isForced=false specified");
                }
            }
        }
    }

    private boolean doCancelMaintenance(long hostId) {
        HostVO host;
        host = _hostDao.findById(hostId);
        if (host == null || host.getRemoved() != null) {
            s_logger.warn("Unable to find host " + hostId);
            return true;
        }

        /*
         * TODO: think twice about returning true or throwing out exception, I
         * really prefer to exception that always exposes bugs
         */
        if (host.getResourceState() != ResourceState.PrepareForMaintenance && host.getResourceState() != ResourceState.Maintenance
                && host.getResourceState() != ResourceState.ErrorInMaintenance) {
            throw new CloudRuntimeException("Cannot perform cancelMaintenance when resource state is " + host.getResourceState() + ", hostId = "
                    + hostId);
        }

        /* TODO: move to listener */
        _haMgr.cancelScheduledMigrations(host);
        List<VMInstanceVO> vms = _haMgr.findTakenMigrationWork();
        for (VMInstanceVO vm : vms) {
            if (vm.getHostId() != null && vm.getHostId() == hostId) {
                s_logger.info("Unable to cancel migration because the vm is being migrated: " + vm);
                return false;
            }
        }

        try {
            resourceStateTransitTo(host, ResourceState.Event.AdminCancelMaintenance, _nodeId);
            _agentMgr.pullAgentOutMaintenance(hostId);

            // for kvm, need to log into kvm host, restart cloudstack-agent
            if (host.getHypervisorType() == HypervisorType.KVM) {

                boolean sshToAgent = Boolean.parseBoolean(_configDao.getValue(Config.KvmSshToAgentEnabled.key()));
                if (!sshToAgent) {
                    s_logger.info("Configuration tells us not to SSH into Agents. Please restart the Agent (" + hostId + ")  manually");
                    return true;
                }

                _hostDao.loadDetails(host);
                String password = host.getDetail("password");
                String username = host.getDetail("username");
                if (password == null || username == null) {
                    s_logger.debug("Can't find password/username");
                    return false;
                }
                com.trilead.ssh2.Connection connection = SSHCmdHelper.acquireAuthorizedConnection(host.getPrivateIpAddress(), 22, username, password);
                if (connection == null) {
                    s_logger.debug("Failed to connect to host: " + host.getPrivateIpAddress());
                    return false;
                }

                try {
                    SSHCmdHelper.sshExecuteCmdOneShot(connection, "service cloudstack-agent restart");
                } catch (sshException e) {
                    return false;
                }
            }

            return true;
        } catch (NoTransitionException e) {
            s_logger.debug("Cannot transmit host " + host.getId() + "to Enabled state", e);
            return false;
        }
    }

    private boolean cancelMaintenance(long hostId) {
        try {
            Boolean result = propagateResourceEvent(hostId, ResourceState.Event.AdminCancelMaintenance);

            if (result != null) {
                return result;
            }
        } catch (AgentUnavailableException e) {
            return false;
        }

        return doCancelMaintenance(hostId);
    }

    @Override
    public boolean executeUserRequest(long hostId, ResourceState.Event event) throws AgentUnavailableException {
        if (event == ResourceState.Event.AdminAskMaintenace) {
            return doMaintain(hostId);
        } else if (event == ResourceState.Event.AdminCancelMaintenance) {
            return doCancelMaintenance(hostId);
        } else if (event == ResourceState.Event.DeleteHost) {
            /* TODO: Ask alex why we assume the last two parameters are false */
            return doDeleteHost(hostId, false, false);
        } else if (event == ResourceState.Event.Unmanaged) {
            return doUmanageHost(hostId);
        } else if (event == ResourceState.Event.UpdatePassword) {
            return doUpdateHostPassword(hostId);
        } else {
            throw new CloudRuntimeException("Received an resource event we are not handling now, " + event);
        }
    }

    private boolean doUmanageHost(long hostId) {
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            s_logger.debug("Cannot find host " + hostId + ", assuming it has been deleted, skip umanage");
            return true;
        }

        if (host.getHypervisorType() == HypervisorType.KVM) {
            MaintainAnswer answer = (MaintainAnswer) _agentMgr.easySend(hostId, new MaintainCommand());
        }

        _agentMgr.disconnectWithoutInvestigation(hostId, Event.ShutdownRequested);
        return true;
    }

    @Override
    public boolean umanageHost(long hostId) {
        try {
            Boolean result = propagateResourceEvent(hostId, ResourceState.Event.Unmanaged);

            if (result != null) {
                return result;
            }
        } catch (AgentUnavailableException e) {
            return false;
        }

        return doUmanageHost(hostId);
    }

    private boolean doUpdateHostPassword(long hostId) {
        if (_agentMgr.isAgentAttached(hostId)) {
            return false;
        }

        DetailVO nv = _hostDetailsDao.findDetail(hostId, ApiConstants.USERNAME);
        String username = nv.getValue();
        nv = _hostDetailsDao.findDetail(hostId, ApiConstants.PASSWORD);
        String password = nv.getValue();
        UpdateHostPasswordCommand cmd = new UpdateHostPasswordCommand(username, password);
        _agentMgr.easySend(hostId, cmd);
        return true;
    }

    @Override
    public boolean updateHostPassword(UpdateHostPasswordCmd cmd) {
        if (cmd.getClusterId() == null) {
            // update agent attache password
            try {
                Boolean result = propagateResourceEvent(cmd.getHostId(), ResourceState.Event.UpdatePassword);
                if (result != null) {
                    return result;
                }
            } catch (AgentUnavailableException e) {
            }

            return doUpdateHostPassword(cmd.getHostId());
        } else {
            // get agents for the cluster
            List<HostVO> hosts = listAllHostsInCluster(cmd.getClusterId());
            for (HostVO h : hosts) {
                try {
                    /*
                     * FIXME: this is a buggy logic, check with alex. Shouldn't
                     * return if propagation return non null
                     */
                    Boolean result = propagateResourceEvent(h.getId(), ResourceState.Event.UpdatePassword);
                    if (result != null) {
                        return result;
                    }

                    doUpdateHostPassword(h.getId());
                } catch (AgentUnavailableException e) {
                }
            }

            return true;
        }
    }

    public String getPeerName(long agentHostId) {

        HostVO host = _hostDao.findById(agentHostId);
        if (host != null && host.getManagementServerId() != null) {
            if (_clusterMgr.getSelfPeerName().equals(Long.toString(host.getManagementServerId()))) {
                return null;
            }

            return Long.toString(host.getManagementServerId());
        }
        return null;
    }

    public Boolean propagateResourceEvent(long agentId, ResourceState.Event event) throws AgentUnavailableException {
        final String msPeer = getPeerName(agentId);
        if (msPeer == null) {
            return null;
        }

        if (s_logger.isDebugEnabled()) {
            s_logger.debug("Propagating agent change request event:" + event.toString() + " to agent:" + agentId);
        }
        Command[] cmds = new Command[1];
        cmds[0] = new PropagateResourceEventCommand(agentId, event);

        String AnsStr = _clusterMgr.execute(msPeer, agentId, _gson.toJson(cmds), true);
        if (AnsStr == null) {
            throw new AgentUnavailableException(agentId);
        }

        Answer[] answers = _gson.fromJson(AnsStr, Answer[].class);

        if (s_logger.isDebugEnabled()) {
            s_logger.debug("Result for agent change is " + answers[0].getResult());
        }

        return answers[0].getResult();
    }

    @Override
    public boolean maintenanceFailed(long hostId) {
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Cant not find host " + hostId);
            }
            return false;
        } else {
            try {
                return resourceStateTransitTo(host, ResourceState.Event.UnableToMigrate, _nodeId);
            } catch (NoTransitionException e) {
                s_logger.debug("No next resource state for host " + host.getId() + " while current state is " + host.getResourceState()
                        + " with event " + ResourceState.Event.UnableToMigrate, e);
                return false;
            }
        }
    }

    @Override
    public List<HostVO> findDirectlyConnectedHosts() {
        /* The resource column is not null for direct connected resource */
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getResource(), Op.NNULL);
        sc.addAnd(sc.getEntity().getResourceState(), Op.NIN, ResourceState.Disabled);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllUpAndEnabledHosts(Type type, Long clusterId, Long podId, long dcId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        if (type != null) {
            sc.addAnd(sc.getEntity().getType(), Op.EQ, type);
        }
        if (clusterId != null) {
            sc.addAnd(sc.getEntity().getClusterId(), Op.EQ, clusterId);
        }
        if (podId != null) {
            sc.addAnd(sc.getEntity().getPodId(), Op.EQ, podId);
        }
        sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        sc.addAnd(sc.getEntity().getStatus(), Op.EQ, Status.Up);
        sc.addAnd(sc.getEntity().getResourceState(), Op.EQ, ResourceState.Enabled);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllUpAndEnabledNonHAHosts(Type type, Long clusterId, Long podId, long dcId) {
        String haTag = _haMgr.getHaTag();
        return _hostDao.listAllUpAndEnabledNonHAHosts(type, clusterId, podId, dcId, haTag);
    }

    @Override
    public List<HostVO> findHostByGuid(long dcId, String guid) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        sc.addAnd(sc.getEntity().getGuid(), Op.EQ, guid);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllHostsInCluster(long clusterId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getClusterId(), Op.EQ, clusterId);
        return sc.list();
    }

    @Override
    public List<HostVO> listHostsInClusterByStatus(long clusterId, Status status) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getClusterId(), Op.EQ, clusterId);
        sc.addAnd(sc.getEntity().getStatus(), Op.EQ, status);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllUpAndEnabledHostsInOneZoneByType(Type type, long dcId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getType(), Op.EQ, type);
        sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        sc.addAnd(sc.getEntity().getStatus(), Op.EQ, Status.Up);
        sc.addAnd(sc.getEntity().getResourceState(), Op.EQ, ResourceState.Enabled);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllNotInMaintenanceHostsInOneZone(Type type, Long dcId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        if (dcId != null) {
            sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        }
        sc.addAnd(sc.getEntity().getType(), Op.EQ, type);
        sc.addAnd(sc.getEntity().getResourceState(), Op.NIN, ResourceState.Maintenance, ResourceState.ErrorInMaintenance,
                ResourceState.PrepareForMaintenance, ResourceState.Error);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllHostsInOneZoneByType(Type type, long dcId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getType(), Op.EQ, type);
        sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        return sc.list();
    }

    @Override
    public List<HostVO> listAllHostsInAllZonesByType(Type type) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getType(), Op.EQ, type);
        return sc.list();
    }

    @Override
    public List<HypervisorType> listAvailHypervisorInZone(Long hostId, Long zoneId) {
        SearchCriteria<String> sc = _hypervisorsInDC.create();
        if (zoneId != null) {
            sc.setParameters("dataCenter", zoneId);
        }
        if (hostId != null) {
            // exclude the given host, since we want to check what hypervisor is already handled
            // in adding this new host
            sc.setParameters("id", hostId);
        }
        sc.setParameters("type", Host.Type.Routing);

        // The search is not able to return list of enums, so getting
        // list of hypervisors as strings and then converting them to enum
        List<String> hvs = _hostDao.customSearch(sc, null);
        List<HypervisorType> hypervisors = new ArrayList<HypervisorType>();
        for (String hv : hvs) {
            hypervisors.add(HypervisorType.getType(hv));
        }
        return hypervisors;
    }

    @Override
    public HostVO findHostByGuid(String guid) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getGuid(), Op.EQ, guid);
        return sc.find();
    }

    @Override
    public HostVO findHostByName(String name) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getName(), Op.EQ, name);
        return sc.find();
    }

    @Override
    public List<HostVO> listHostsByNameLike(String name) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getName(), Op.LIKE, "%" + name + "%");
        return sc.list();
    }

    @Override
    public Pair<Pod, Long> findPod(VirtualMachineTemplate template, ServiceOffering offering, DataCenter dc, long accountId,
            Set<Long> avoids) {
        for (PodAllocator allocator : _podAllocators) {
            final Pair<Pod, Long> pod = allocator.allocateTo(template, offering, dc, accountId, avoids);
            if (pod != null) {
                return pod;
            }
        }
        return null;
    }

    @Override
    public HostStats getHostStatistics(long hostId) {
        Answer answer = _agentMgr.easySend(hostId, new GetHostStatsCommand(_hostDao.findById(hostId).getGuid(), _hostDao.findById(hostId).getName(),
                hostId));

        if (answer != null && (answer instanceof UnsupportedAnswer)) {
            return null;
        }

        if (answer == null || !answer.getResult()) {
            String msg = "Unable to obtain host " + hostId + " statistics. ";
            s_logger.warn(msg);
            return null;
        } else {

            // now construct the result object
            if (answer instanceof GetHostStatsAnswer) {
                return ((GetHostStatsAnswer) answer).getHostStats();
            }
        }
        return null;
    }

    @Override
    public Long getGuestOSCategoryId(long hostId) {
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            return null;
        } else {
            _hostDao.loadDetails(host);
            DetailVO detail = _hostDetailsDao.findDetail(hostId, "guest.os.category.id");
            if (detail == null) {
                return null;
            } else {
                return Long.parseLong(detail.getValue());
            }
        }
    }

    @Override
    public String getHostTags(long hostId) {
        List<String> hostTags = _hostTagsDao.gethostTags(hostId);
        if (hostTags == null) {
            return null;
        } else {
            return StringUtils.listToCsvTags(hostTags);
        }
    }

    @Override
    public List<PodCluster> listByDataCenter(long dcId) {
        List<HostPodVO> pods = _podDao.listByDataCenterId(dcId);
        ArrayList<PodCluster> pcs = new ArrayList<PodCluster>();
        for (HostPodVO pod : pods) {
            List<ClusterVO> clusters = _clusterDao.listByPodId(pod.getId());
            if (clusters.size() == 0) {
                pcs.add(new PodCluster(pod, null));
            } else {
                for (ClusterVO cluster : clusters) {
                    pcs.add(new PodCluster(pod, cluster));
                }
            }
        }
        return pcs;
    }

    @Override
    public List<HostVO> listAllUpAndEnabledHostsInOneZoneByHypervisor(HypervisorType type, long dcId) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        sc.addAnd(sc.getEntity().getHypervisorType(), Op.EQ, type);
        sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, dcId);
        sc.addAnd(sc.getEntity().getStatus(), Op.EQ, Status.Up);
        sc.addAnd(sc.getEntity().getResourceState(), Op.EQ, ResourceState.Enabled);
        return sc.list();
    }

    @Override
    @DB
    @ActionEvent(eventType = EventTypes.EVENT_HOST_RESERVATION_RELEASE, eventDescription = "releasing host reservation", async = true)
    public boolean releaseHostReservation(Long hostId) {
        Transaction txn = Transaction.currentTxn();
        try {
            txn.start();
            PlannerHostReservationVO reservationEntry = _plannerHostReserveDao.findByHostId(hostId);
            if (reservationEntry != null) {
                long id = reservationEntry.getId();
                PlannerHostReservationVO hostReservation = _plannerHostReserveDao.lockRow(id, true);
                if (hostReservation == null) {
                    if (s_logger.isDebugEnabled()) {
                        s_logger.debug("Host reservation for host: " + hostId + " does not even exist.  Release reservartion call is ignored.");
                    }
                    txn.rollback();
                    return false;
                }
                hostReservation.setResourceUsage(null);
                _plannerHostReserveDao.persist(hostReservation);
                txn.commit();
                return true;
            }
            if (s_logger.isDebugEnabled()) {
                s_logger.debug("Host reservation for host: " + hostId
                        + " does not even exist.  Release reservartion call is ignored.");
            }
            return false;
        } catch (CloudRuntimeException e) {
            throw e;
        } catch (Throwable t) {
            s_logger.error("Unable to release host reservation for host: " + hostId, t);
            txn.rollback();
            return false;
        }
    }
}