// 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.Enumeration;
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.naming.ConfigurationException;

import org.apache.log4j.Logger;

import com.cloud.agent.AgentManager;
import com.cloud.agent.AgentManager.TapAgentsAction;
import com.cloud.agent.api.Answer;
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.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.allocator.PodAllocator;
import com.cloud.agent.transport.Request;
import com.cloud.api.ApiConstants;
import com.cloud.api.ApiDBUtils;
import com.cloud.api.commands.AddClusterCmd;
import com.cloud.api.commands.AddHostCmd;
import com.cloud.api.commands.AddSecondaryStorageCmd;
import com.cloud.api.commands.AddSwiftCmd;
import com.cloud.api.commands.CancelMaintenanceCmd;
import com.cloud.api.commands.DeleteClusterCmd;
import com.cloud.api.commands.ListSwiftsCmd;
import com.cloud.api.commands.PrepareForMaintenanceCmd;
import com.cloud.api.commands.ReconnectHostCmd;
import com.cloud.api.commands.UpdateHostCmd;
import com.cloud.api.commands.UpdateHostPasswordCmd;
import com.cloud.capacity.Capacity;
import com.cloud.capacity.CapacityVO;
import com.cloud.capacity.dao.CapacityDao;
import com.cloud.cluster.ClusterManager;
import com.cloud.cluster.ManagementServerNode;
import com.cloud.configuration.Config;
import com.cloud.configuration.ConfigurationManager;
import com.cloud.configuration.dao.ConfigurationDao;
import com.cloud.dc.ClusterDetailsDao;
import com.cloud.dc.ClusterVO;
import com.cloud.dc.ClusterVSMMapVO;
import com.cloud.dc.DataCenterIpAddressVO;
import com.cloud.dc.DataCenterVO;
import com.cloud.dc.HostPodVO;
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.HostPodDao;
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.IPAddressVO;
import com.cloud.network.dao.IPAddressDao;
import com.cloud.org.Cluster;
import com.cloud.org.Grouping;
import com.cloud.org.Grouping.AllocationState;
import com.cloud.org.Managed;
import com.cloud.service.ServiceOfferingVO;
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.StoragePoolVO;
import com.cloud.storage.StorageService;
import com.cloud.storage.Swift;
import com.cloud.storage.SwiftVO;
import com.cloud.storage.VMTemplateVO;
import com.cloud.storage.dao.GuestOSCategoryDao;
import com.cloud.storage.dao.StoragePoolDao;
import com.cloud.storage.dao.StoragePoolHostDao;
import com.cloud.storage.dao.VMTemplateDao;
import com.cloud.storage.secondary.SecondaryStorageVmManager;
import com.cloud.storage.swift.SwiftManager;
import com.cloud.template.VirtualMachineTemplate;
import com.cloud.user.Account;
import com.cloud.user.AccountManager;
import com.cloud.user.User;
import com.cloud.user.UserContext;
import com.cloud.utils.Pair;
import com.cloud.utils.StringUtils;
import com.cloud.utils.UriUtils;
import com.cloud.utils.cisco.n1kv.vsm.NetconfHelper;
import com.cloud.utils.component.Adapters;
import com.cloud.utils.component.Inject;
import com.cloud.utils.component.Manager;
import com.cloud.utils.db.DB;
import com.cloud.utils.db.SearchCriteria;
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;

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

    private String                           _name;

    @Inject
    AccountManager                           _accountMgr;
    @Inject
    AgentManager                             _agentMgr;
    @Inject
    StorageManager                           _storageMgr;
    @Inject
    protected SecondaryStorageVmManager      _secondaryStorageMgr;

    @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 SwiftManager _swiftMgr;
    @Inject
    protected HostDetailsDao                 _hostDetailsDao;
    @Inject
    protected ConfigurationDao _configDao;
    @Inject
    protected HostTagsDao                    _hostTagsDao;    
    @Inject
    protected GuestOSCategoryDao             _guestOSCategoryDao;
    @Inject 
    protected StoragePoolDao                _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(adapter = Discoverer.class)
    protected Adapters<? extends Discoverer> _discoverers;
    @Inject
    protected ClusterManager                 _clusterMgr;
    @Inject
    protected StoragePoolHostDao             _storagePoolHostDao;
    @Inject(adapter = PodAllocator.class)
    protected Adapters<PodAllocator> _podAllocators = null;
    @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 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(zone, dcId, "dcId");
            throw ex;
        }

        Account account = UserContext.current().getCaller();
        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, dcId, "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, podId, "podId");
            ex.addProxyObject(zone, dcId, "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 ");
        }

        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());
        }

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

        long clusterId = 0;
        ClusterVO cluster = new ClusterVO(dcId, podId, clusterName);
        cluster.setHypervisorType(cmd.getHypervisor());

        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, podId, "podId");
            ex.addProxyObject(zone, dcId, "dcId");
            throw ex;
        }
        clusterId = cluster.getId();
        result.add(cluster);

        if (clusterType == Cluster.ClusterType.CloudManaged) {
            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);
        _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, clusterId, uri, username, password, null);

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

                    // For Hyper-V, we are here means agent have already started and connected to management server
                    if (hypervisorType == Hypervisor.HypervisorType.Hyperv) {
                        break;
                    }

                    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(clusterId);
                _clusterDao.remove(clusterId);
            }
        }
    }

    @Override
    public Discoverer getMatchingDiscover(Hypervisor.HypervisorType hypervisorType) {
        Enumeration<? extends Discoverer> en = _discoverers.enumeration();
        while (en.hasMoreElements()) {
            Discoverer discoverer = en.nextElement();
            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(UserContext.current().getCaller(), 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(cluster, clusterId, "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, clusterId, "clusterId");
                        throw ex;
                    }
                }
            }
        }

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

    @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);
    }

    @Override
    public Swift discoverSwift(AddSwiftCmd cmd) throws DiscoveryException {
        return _swiftMgr.addSwift(cmd);
    }

    @Override
    public List<SwiftVO> listSwifts(ListSwiftsCmd cmd) {
        return _swiftMgr.listSwifts(cmd);
    }

    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) 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 = UserContext.current().getCaller();
        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, dcId, "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, podId, "podId");
                ex.addProxyObject(zone, dcId, "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 = this._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, podId, "podId");
                    ex.addProxyObject(zone, dcId, "dcId");
                    throw ex;   
                }
            }
            clusterId = cluster.getId();
        }

        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);
        Enumeration<? extends Discoverer> en = _discoverers.enumeration();
        boolean isHypervisorTypeSupported = false;
        while (en.hasMoreElements()) {
            Discoverer discoverer = en.nextElement();
            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 = (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(UserContext.current().getCallerUserId());
        // Verify that host exists
        HostVO host = _hostDao.findById(hostId);
        if (host == null) {
            throw new InvalidParameterValueException("Host with id " + hostId + " doesn't exist");            
        }
        _accountMgr.checkAccessAndSpecifyAuthority(UserContext.current().getCaller(), host.getDataCenterId());

        /*
         * TODO: check current agent status and updateAgentStatus to removed. If it was already removed, that means
         * someone is deleting host concurrently, return. And consider the situation of CloudStack shutdown during delete.
         * A global lock?
         * 
         */
        AgentAttache attache = _agentMgr.findAttache(hostId);
        // 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);

        // 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);
        txn.commit();
        return true;
    }

    @Override
    public boolean deleteHost(long hostId, boolean isForced, boolean isForceDeleteStorage) {
        try {
            Boolean result = _clusterMgr.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());
                }
            }

            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 = _clusterMgr.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)) {
            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 {
        _name = name;
        _defaultSystemVMHypervisor = HypervisorType.getType(_configDao.getValue(Config.SystemVMDefaultHypervisor.toString()));
        return true;
    }

    @Override
    public boolean start() {
        return true;
    }

    @Override
    public boolean stop() {
        return true;
    }

    @Override
    public String getName() {
        return _name;
    }

    @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) {
                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 it = _resourceStateAdapters.entrySet().iterator();
            Object result = null;
            while (it.hasNext()) {
                Map.Entry<String, ResourceStateAdapter> item = (Map.Entry<String, ResourceStateAdapter>) 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 Host createHostAndAgent(ServerResource resource, Map<String, String> details, boolean old, List<String> hostTags,
            boolean forRebalance) {
        HostVO host = null;
        AgentAttache attache = null;
        StartupCommand[] cmds = null;

        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) {
                    s_logger.debug("Found the host " + host.getId() + " by guid: " + firstCmd.getGuid() + ", old host reconnected as new");
                    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 (attache == null) {
                if (cmds != null) {
                    resource.disconnected();
                }
                //In case of some db errors, we may land with the sitaution that host is null. We need to reload host from db and call disconnect on it so that it will be loaded for reconnection next time
                HostVO tempHost = host;
                if(tempHost == null){
                    if (cmds != null) {
                        StartupCommand firstCmd = cmds[0];
                        tempHost = findHostByGuid(firstCmd.getGuid());
                        if (tempHost == null) {
                            tempHost = findHostByGuid(firstCmd.getGuidWithoutResource());
                        }
                    }
                }
                
                if (tempHost != null) {
                    /* Change agent status to Alert */
                    _agentMgr.agentStatusTransitTo(tempHost, Status.Event.AgentDisconnected, _nodeId);
                    /* Don't change resource state here since HostVO is already in database, which means resource state has had an appropriate value*/
                }
            }
        }

        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 = this.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);        
        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());
        }

        User caller = _accountMgr.getActiveUser(UserContext.current().getCallerUserId());
        if (forceDestroyStorage) {
            // put local storage into mainenance mode, will set all the VMs on
            // this local storage into stopped state
            StoragePool storagePool = _storageMgr.findLocalStorageOnHost(host.getId());
            if (storagePool != null) {
                if (storagePool.getStatus() == StoragePoolStatus.Up || storagePool.getStatus() == StoragePoolStatus.ErrorInMaintenance) {
                    try {
                        storagePool = _storageSvr.preparePrimaryStorageForMaintenance(storagePool.getId());
                        if (storagePool == 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 {
                        if (!_vmMgr.destroy(vm, caller, _accountMgr.getAccount(vm.getAccountId()))) {
                            String errorMsg = "There was an error Destory the vm: " + vm + " as a part of hostDelete id=" + host.getId();
                            s_logger.warn(errorMsg);
                            throw new UnableDeleteHostException(errorMsg);
                        }
                    } 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 {
                                if (!_vmMgr.advanceStop(vm, true, caller, _accountMgr.getAccount(vm.getAccountId()))) {
                                    String errorMsg = "There was an error stopping the vm: " + vm + " as a part of hostDelete id=" + host.getId();
                                    s_logger.warn(errorMsg);
                                    throw new UnableDeleteHostException(errorMsg);
                                }
                            } 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 cloud-agent
            if (host.getHypervisorType() == HypervisorType.KVM) {
                _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 cloud-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 = _clusterMgr.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 = _clusterMgr.propagateResourceEvent(hostId, ResourceState.Event.Unmanaged);

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

        return doUmanageHost(hostId);
    }

    private boolean doUpdateHostPassword(long hostId) {
        AgentAttache attache = _agentMgr.findAttache(hostId);
        if (attache == null) {
            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);
        attache.updatePassword(cmd);
        return true;
    }

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

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

            return true;
        }
    }

    @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) {
        SearchCriteriaService<HostVO, HostVO> sc = SearchCriteria2.create(HostVO.class);
        if (zoneId != null) {
            sc.addAnd(sc.getEntity().getDataCenterId(), Op.EQ, zoneId);
        }
        if (hostId != null) {
            sc.addAnd(sc.getEntity().getId(), Op.EQ, hostId);
        }
        sc.addAnd(sc.getEntity().getType(), Op.EQ, Host.Type.Routing);
        List<HostVO> hosts = sc.list();

        List<HypervisorType> hypers = new ArrayList<HypervisorType>(5);
        for (HostVO host : hosts) {
            hypers.add(host.getHypervisorType());
        }
        return hypers;
    }

    @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<HostPodVO, Long> findPod(VirtualMachineTemplate template, ServiceOfferingVO offering, DataCenterVO dc, long accountId, Set<Long> avoids) {
        final Enumeration en = _podAllocators.enumeration();
        while (en.hasMoreElements()) {
            final PodAllocator allocator = (PodAllocator) en.nextElement();
            final Pair<HostPodVO, 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;
    }
}