protected Long restart(HaWorkVO work) {
    List<HaWorkVO> items = _haDao.listFutureHaWorkForVm(work.getInstanceId(), work.getId());
    if (items.size() > 0) {
      StringBuilder str =
          new StringBuilder(
              "Cancelling this work item because newer ones have been scheduled.  Work Ids = [");
      for (HaWorkVO item : items) {
        str.append(item.getId()).append(", ");
      }
      str.delete(str.length() - 2, str.length()).append("]");
      s_logger.info(str.toString());
      return null;
    }

    items = _haDao.listRunningHaWorkForVm(work.getInstanceId());
    if (items.size() > 0) {
      StringBuilder str =
          new StringBuilder(
              "Waiting because there's HA work being executed on an item currently.  Work Ids =[");
      for (HaWorkVO item : items) {
        str.append(item.getId()).append(", ");
      }
      str.delete(str.length() - 2, str.length()).append("]");
      s_logger.info(str.toString());
      return (System.currentTimeMillis() >> 10) + _investigateRetryInterval;
    }

    long vmId = work.getInstanceId();

    VMInstanceVO vm = _itMgr.findByIdAndType(work.getType(), work.getInstanceId());
    if (vm == null) {
      s_logger.info("Unable to find vm: " + vmId);
      return null;
    }

    s_logger.info("HA on " + vm);
    if (vm.getState() != work.getPreviousState() || vm.getUpdated() != work.getUpdateTime()) {
      s_logger.info(
          "VM "
              + vm
              + " has been changed.  Current State = "
              + vm.getState()
              + " Previous State = "
              + work.getPreviousState()
              + " last updated = "
              + vm.getUpdated()
              + " previous updated = "
              + work.getUpdateTime());
      return null;
    }

    short alertType = AlertManager.ALERT_TYPE_USERVM;
    if (VirtualMachine.Type.DomainRouter.equals(vm.getType())) {
      alertType = AlertManager.ALERT_TYPE_DOMAIN_ROUTER;
    } else if (VirtualMachine.Type.ConsoleProxy.equals(vm.getType())) {
      alertType = AlertManager.ALERT_TYPE_CONSOLE_PROXY;
    } else if (VirtualMachine.Type.SecondaryStorageVm.equals(vm.getType())) {
      alertType = AlertManager.ALERT_TYPE_SSVM;
    }

    HostVO host = _hostDao.findById(work.getHostId());
    boolean isHostRemoved = false;
    if (host == null) {
      host = _hostDao.findByIdIncludingRemoved(work.getHostId());
      if (host != null) {
        s_logger.debug(
            "VM "
                + vm.toString()
                + " is now no longer on host "
                + work.getHostId()
                + " as the host is removed");
        isHostRemoved = true;
      }
    }

    DataCenterVO dcVO = _dcDao.findById(host.getDataCenterId());
    HostPodVO podVO = _podDao.findById(host.getPodId());
    String hostDesc =
        "name: "
            + host.getName()
            + "(id:"
            + host.getId()
            + "), availability zone: "
            + dcVO.getName()
            + ", pod: "
            + podVO.getName();

    Boolean alive = null;
    if (work.getStep() == Step.Investigating) {
      if (!isHostRemoved) {
        if (vm.getHostId() == null || vm.getHostId() != work.getHostId()) {
          s_logger.info("VM " + vm.toString() + " is now no longer on host " + work.getHostId());
          return null;
        }

        Enumeration<Investigator> en = _investigators.enumeration();
        Investigator investigator = null;
        while (en.hasMoreElements()) {
          investigator = en.nextElement();
          alive = investigator.isVmAlive(vm, host);
          s_logger.info(investigator.getName() + " found " + vm + "to be alive? " + alive);
          if (alive != null) {
            break;
          }
        }
        boolean fenced = false;
        if (alive == null) {
          s_logger.debug("Fencing off VM that we don't know the state of");
          Enumeration<FenceBuilder> enfb = _fenceBuilders.enumeration();
          while (enfb.hasMoreElements()) {
            FenceBuilder fb = enfb.nextElement();
            Boolean result = fb.fenceOff(vm, host);
            s_logger.info("Fencer " + fb.getName() + " returned " + result);
            if (result != null && result) {
              fenced = true;
              break;
            }
          }
        } else if (!alive) {
          fenced = true;
        } else {
          s_logger.debug(
              "VM " + vm.getHostName() + " is found to be alive by " + investigator.getName());
          if (host.getStatus() == Status.Up) {
            s_logger.info(vm + " is alive and host is up. No need to restart it.");
            return null;
          } else {
            s_logger.debug("Rescheduling because the host is not up but the vm is alive");
            return (System.currentTimeMillis() >> 10) + _investigateRetryInterval;
          }
        }

        if (!fenced) {
          s_logger.debug("We were unable to fence off the VM " + vm);
          _alertMgr.sendAlert(
              alertType,
              vm.getDataCenterIdToDeployIn(),
              vm.getPodIdToDeployIn(),
              "Unable to restart " + vm.getHostName() + " which was running on host " + hostDesc,
              "Insufficient capacity to restart VM, name: "
                  + vm.getHostName()
                  + ", id: "
                  + vmId
                  + " which was running on host "
                  + hostDesc);
          return (System.currentTimeMillis() >> 10) + _restartRetryInterval;
        }

        try {
          _itMgr.advanceStop(vm, true, _accountMgr.getSystemUser(), _accountMgr.getSystemAccount());
        } catch (ResourceUnavailableException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        } catch (OperationTimedoutException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        } catch (ConcurrentOperationException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        }

        work.setStep(Step.Scheduled);
        _haDao.update(work.getId(), work);
      } else {
        s_logger.debug(
            "How come that HA step is Investigating and the host is removed? Calling forced Stop on Vm anyways");
        try {
          _itMgr.advanceStop(vm, true, _accountMgr.getSystemUser(), _accountMgr.getSystemAccount());
        } catch (ResourceUnavailableException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        } catch (OperationTimedoutException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        } catch (ConcurrentOperationException e) {
          assert false : "How do we hit this when force is true?";
          throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
        }
      }
    }

    vm = _itMgr.findByIdAndType(vm.getType(), vm.getId());

    if (!_forceHA && !vm.isHaEnabled()) {
      if (s_logger.isDebugEnabled()) {
        s_logger.debug("VM is not HA enabled so we're done.");
      }
      return null; // VM doesn't require HA
    }

    if (!_storageMgr.canVmRestartOnAnotherServer(vm.getId())) {
      if (s_logger.isDebugEnabled()) {
        s_logger.debug("VM can not restart on another server.");
      }
      return null;
    }

    if (work.getTimesTried() > _maxRetries) {
      s_logger.warn("Retried to max times so deleting: " + vmId);
      return null;
    }

    try {
      VMInstanceVO started =
          _itMgr.advanceStart(
              vm,
              new HashMap<VirtualMachineProfile.Param, Object>(),
              _accountMgr.getSystemUser(),
              _accountMgr.getSystemAccount());
      if (started != null) {
        s_logger.info("VM is now restarted: " + vmId + " on " + started.getHostId());
        return null;
      }

      if (s_logger.isDebugEnabled()) {
        s_logger.debug(
            "Rescheduling VM " + vm.toString() + " to try again in " + _restartRetryInterval);
      }
    } catch (final InsufficientCapacityException e) {
      s_logger.warn("Unable to restart " + vm.toString() + " due to " + e.getMessage());
      _alertMgr.sendAlert(
          alertType,
          vm.getDataCenterIdToDeployIn(),
          vm.getPodIdToDeployIn(),
          "Unable to restart " + vm.getHostName() + " which was running on host " + hostDesc,
          "Insufficient capacity to restart VM, name: "
              + vm.getHostName()
              + ", id: "
              + vmId
              + " which was running on host "
              + hostDesc);
    } catch (final ResourceUnavailableException e) {
      s_logger.warn("Unable to restart " + vm.toString() + " due to " + e.getMessage());
      _alertMgr.sendAlert(
          alertType,
          vm.getDataCenterIdToDeployIn(),
          vm.getPodIdToDeployIn(),
          "Unable to restart " + vm.getHostName() + " which was running on host " + hostDesc,
          "The Storage is unavailable for trying to restart VM, name: "
              + vm.getHostName()
              + ", id: "
              + vmId
              + " which was running on host "
              + hostDesc);
    } catch (ConcurrentOperationException e) {
      s_logger.warn("Unable to restart " + vm.toString() + " due to " + e.getMessage());
      _alertMgr.sendAlert(
          alertType,
          vm.getDataCenterIdToDeployIn(),
          vm.getPodIdToDeployIn(),
          "Unable to restart " + vm.getHostName() + " which was running on host " + hostDesc,
          "The Storage is unavailable for trying to restart VM, name: "
              + vm.getHostName()
              + ", id: "
              + vmId
              + " which was running on host "
              + hostDesc);
    } catch (OperationTimedoutException e) {
      s_logger.warn("Unable to restart " + vm.toString() + " due to " + e.getMessage());
      _alertMgr.sendAlert(
          alertType,
          vm.getDataCenterIdToDeployIn(),
          vm.getPodIdToDeployIn(),
          "Unable to restart " + vm.getHostName() + " which was running on host " + hostDesc,
          "The Storage is unavailable for trying to restart VM, name: "
              + vm.getHostName()
              + ", id: "
              + vmId
              + " which was running on host "
              + hostDesc);
    }
    vm = _itMgr.findByIdAndType(vm.getType(), vm.getId());
    work.setUpdateTime(vm.getUpdated());
    work.setPreviousState(vm.getState());
    return (System.currentTimeMillis() >> 10) + _restartRetryInterval;
  }
  @Override
  public void scheduleRestart(VMInstanceVO vm, boolean investigate) {
    Long hostId = vm.getHostId();
    if (hostId == null) {
      try {
        s_logger.debug("Found a vm that is scheduled to be restarted but has no host id: " + vm);
        _itMgr.advanceStop(vm, true, _accountMgr.getSystemUser(), _accountMgr.getSystemAccount());
      } catch (ResourceUnavailableException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      } catch (OperationTimedoutException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      } catch (ConcurrentOperationException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      }
      return;
    }

    if (vm.getHypervisorType() == HypervisorType.VMware) {
      s_logger.info("Skip HA for VMware VM " + vm.getInstanceName());
      return;
    }

    if (!investigate) {
      if (s_logger.isDebugEnabled()) {
        s_logger.debug(
            "VM does not require investigation so I'm marking it as Stopped: " + vm.toString());
      }

      short alertType = AlertManager.ALERT_TYPE_USERVM;
      if (VirtualMachine.Type.DomainRouter.equals(vm.getType())) {
        alertType = AlertManager.ALERT_TYPE_DOMAIN_ROUTER;
      } else if (VirtualMachine.Type.ConsoleProxy.equals(vm.getType())) {
        alertType = AlertManager.ALERT_TYPE_CONSOLE_PROXY;
      } else if (VirtualMachine.Type.SecondaryStorageVm.equals(vm.getType())) {
        alertType = AlertManager.ALERT_TYPE_SSVM;
      }

      if (!(_forceHA || vm.isHaEnabled())) {
        String hostDesc =
            "id:"
                + vm.getHostId()
                + ", availability zone id:"
                + vm.getDataCenterIdToDeployIn()
                + ", pod id:"
                + vm.getPodIdToDeployIn();
        _alertMgr.sendAlert(
            alertType,
            vm.getDataCenterIdToDeployIn(),
            vm.getPodIdToDeployIn(),
            "VM (name: "
                + vm.getHostName()
                + ", id: "
                + vm.getId()
                + ") stopped unexpectedly on host "
                + hostDesc,
            "Virtual Machine "
                + vm.getHostName()
                + " (id: "
                + vm.getId()
                + ") running on host ["
                + vm.getHostId()
                + "] stopped unexpectedly.");

        if (s_logger.isDebugEnabled()) {
          s_logger.debug("VM is not HA enabled so we're done.");
        }
      }

      try {
        _itMgr.advanceStop(vm, true, _accountMgr.getSystemUser(), _accountMgr.getSystemAccount());
      } catch (ResourceUnavailableException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      } catch (OperationTimedoutException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      } catch (ConcurrentOperationException e) {
        assert false : "How do we hit this when force is true?";
        throw new CloudRuntimeException("Caught exception even though it should be handled.", e);
      }
    }

    List<HaWorkVO> items = _haDao.findPreviousHA(vm.getId());
    int maxRetries = 0;
    for (HaWorkVO item : items) {
      if (maxRetries < item.getTimesTried() && !item.canScheduleNew(_timeBetweenFailures)) {
        maxRetries = item.getTimesTried();
        break;
      }
    }

    HaWorkVO work =
        new HaWorkVO(
            vm.getId(),
            vm.getType(),
            WorkType.HA,
            investigate ? Step.Investigating : Step.Scheduled,
            hostId,
            vm.getState(),
            maxRetries + 1,
            vm.getUpdated());
    _haDao.persist(work);

    if (s_logger.isInfoEnabled()) {
      s_logger.info("Schedule vm for HA:  " + vm);
    }

    wakeupWorkers();
  }