Fix: Select another pod if all hosts in the pod becomes unavailable (#8085)

Author: vishesh92

engine/orchestration/src/main/java/com/cloud/vm/VirtualMachineManagerImpl.java

@@ -569,7 +569,7 @@ public void allocate(final String vmInstanceName, final VirtualMachineTemplate t
         allocate(vmInstanceName, template, serviceOffering, new DiskOfferingInfo(diskOffering), new ArrayList<>(), networks, plan, hyperType, null, null);
     }
 
-    private VirtualMachineGuru getVmGuru(final VirtualMachine vm) {
+    VirtualMachineGuru getVmGuru(final VirtualMachine vm) {
         if(vm != null) {
             return _vmGurus.get(vm.getType());
         }
@@ -1443,6 +1443,7 @@ public void orchestrateStart(final String vmUuid, final Map<VirtualMachineProfil
                 }
                 if (canRetry) {
                     try {
+                        conditionallySetPodToDeployIn(vm);
                         changeState(vm, Event.OperationFailed, null, work, Step.Done);
                     } catch (final NoTransitionException e) {
                         throw new ConcurrentOperationException(e.getMessage());
@@ -1460,6 +1461,24 @@ public void orchestrateStart(final String vmUuid, final Map<VirtualMachineProfil
         }
     }
 
+    /**
+     * Setting pod id to null can result in migration of Volumes across pods. This is not desirable for VMs which
+     * have a volume in Ready state (happens when a VM is shutdown and started again).
+     * So, we set it to null only when
+     * migration of VM across cluster is enabled
+     * Or, volumes are still in allocated state for that VM (happens when VM is Starting/deployed for the first time)
+     */
+    private void conditionallySetPodToDeployIn(VMInstanceVO vm) {
+        if (MIGRATE_VM_ACROSS_CLUSTERS.valueIn(vm.getDataCenterId()) || areAllVolumesAllocated(vm.getId())) {
+            vm.setPodIdToDeployIn(null);
+        }
+    }
+
+    boolean areAllVolumesAllocated(long vmId) {
+        final List<VolumeVO> vols = _volsDao.findByInstance(vmId);
+        return CollectionUtils.isEmpty(vols) || vols.stream().allMatch(v -> Volume.State.Allocated.equals(v.getState()));
+    }
+
     private void logBootModeParameters(Map<VirtualMachineProfile.Param, Object> params) {
         if (params == null) {
           return;