server/src/com/cloud/ha/HighAvailabilityManager.java

/**
 *  Copyright (C) 2010 Cloud.com, Inc.  All rights reserved.
 * 
 * This software is licensed under the GNU General Public License v3 or later.
 * 
 * It is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */
package com.cloud.ha;

import java.util.List;

import com.cloud.host.HostVO;
import com.cloud.host.Status;
import com.cloud.utils.component.Manager;
import com.cloud.vm.VMInstanceVO;

/**
 * HighAvailabilityManager checks to make sure the VMs are running fine.
 */
public interface HighAvailabilityManager extends Manager {
    public enum WorkType {
        Migration,  // Migrating VMs off of a host.
        Stop,       // Stops a VM for storage pool migration purposes.  This should be obsolete now.
        CheckStop,  // Checks if a VM has been stopped.
        ForceStop,  // Force a VM to stop even if the states don't allow it.  Use this only if you know the VM is stopped on the physical hypervisor.
        Destroy,    // Destroy a VM.
        HA;         // Restart a VM.
    }

    enum Step {
        Scheduled,
        Investigating,
        Fencing,
        Stopping,
        Restarting,
        Migrating,
        Cancelled,
        Done,
        Error,
    }

    /**
     * Investigate why a host has disconnected and migrate the VMs on it
     * if necessary.
     * 
     * @param host - the host that has disconnected.
     */
    Status investigate(long hostId);

    /**
     * Restart a vm that has gone away due to various reasons.  Whether a
     * VM is restarted depends on various reasons.
     *   1. Is the VM really dead.  This method will try to find out.
     *   2. Is the VM HA enabled?  If not, the VM is simply stopped.
     * 
     * All VMs that enter HA mode is not allowed to be operated on until it
     * has been determined that the VM is dead.
     * 
     * @param vm the vm that has gone away.
     * @param investigate must be investigated before we do anything with this vm.
     */
    void scheduleRestart(VMInstanceVO vm, boolean investigate);

    void cancelDestroy(VMInstanceVO vm, Long hostId);
    
    void scheduleDestroy(VMInstanceVO vm, long hostId);
    
    /**
     * Schedule restarts for all vms running on the host.
     * @param host host.
     */
    void scheduleRestartForVmsOnHost(HostVO host);

    /**
     * Schedule the vm for migration.
     * 
     * @param vm
     * @return true if schedule worked.
     */
    boolean scheduleMigration(VMInstanceVO vm);
    
    List<VMInstanceVO> findTakenMigrationWork();

    /**
     * Schedules a work item to stop a VM.  This method schedules a work
     * item to do one of three things.
     * 
     * 1. Perform a regular stop of a VM: WorkType.Stop
     * 2. Perform a force stop of a VM: WorkType.ForceStop
     * 3. Check if a VM has been stopped: WorkType.CheckStop
     * 
     * @param vm virtual machine to stop.
     * @param host host the virtual machine is on.
     * @param type which type of stop is requested. 
     */
    void scheduleStop(VMInstanceVO vm, long hostId, WorkType type);

    void cancelScheduledMigrations(HostVO host);
}