protected void assertThatTheRightLibvirtApiIsInvokedForRunInstance() throws Exception {
    int[] domains = stubLibvirtConnection.listDomains();
    assertEquals(1, domains.length);

    Domain domain = stubLibvirtConnection.domainLookupByID(domains[0]);
    assertEquals(domain.getName(), instanceId);

    String domainXml = domain.getXMLDesc(0);
    assertThatDomainXmlContainsNecessaryFields(domainXml);
  }
  @Override
  public Answer execute(
      final BackupSnapshotCommand command,
      final LibvirtComputingResource libvirtComputingResource) {
    final Long dcId = command.getDataCenterId();
    final Long accountId = command.getAccountId();
    final Long volumeId = command.getVolumeId();
    final String secondaryStoragePoolUrl = command.getSecondaryStorageUrl();
    final String snapshotName = command.getSnapshotName();
    String snapshotDestPath = null;
    String snapshotRelPath = null;
    final String vmName = command.getVmName();
    KVMStoragePool secondaryStoragePool = null;
    final KVMStoragePoolManager storagePoolMgr = libvirtComputingResource.getStoragePoolMgr();

    try {
      final LibvirtUtilitiesHelper libvirtUtilitiesHelper =
          libvirtComputingResource.getLibvirtUtilitiesHelper();
      final Connect conn = libvirtUtilitiesHelper.getConnectionByVmName(vmName);

      secondaryStoragePool = storagePoolMgr.getStoragePoolByURI(secondaryStoragePoolUrl);

      final String ssPmountPath = secondaryStoragePool.getLocalPath();
      snapshotRelPath =
          File.separator
              + "snapshots"
              + File.separator
              + dcId
              + File.separator
              + accountId
              + File.separator
              + volumeId;

      snapshotDestPath =
          ssPmountPath
              + File.separator
              + "snapshots"
              + File.separator
              + dcId
              + File.separator
              + accountId
              + File.separator
              + volumeId;
      final KVMStoragePool primaryPool =
          storagePoolMgr.getStoragePool(
              command.getPool().getType(), command.getPrimaryStoragePoolNameLabel());
      final KVMPhysicalDisk snapshotDisk = primaryPool.getPhysicalDisk(command.getVolumePath());

      final String manageSnapshotPath = libvirtComputingResource.manageSnapshotPath();
      final int cmdsTimeout = libvirtComputingResource.getCmdsTimeout();

      /**
       * RBD snapshots can't be copied using qemu-img, so we have to use the Java bindings for
       * librbd here.
       *
       * <p>These bindings will read the snapshot and write the contents to the secondary storage
       * directly
       *
       * <p>It will stop doing so if the amount of time spend is longer then cmds.timeout
       */
      if (primaryPool.getType() == StoragePoolType.RBD) {
        try {
          final Rados r = new Rados(primaryPool.getAuthUserName());
          r.confSet("mon_host", primaryPool.getSourceHost() + ":" + primaryPool.getSourcePort());
          r.confSet("key", primaryPool.getAuthSecret());
          r.confSet("client_mount_timeout", "30");
          r.connect();
          s_logger.debug("Succesfully connected to Ceph cluster at " + r.confGet("mon_host"));

          final IoCTX io = r.ioCtxCreate(primaryPool.getSourceDir());
          final Rbd rbd = new Rbd(io);
          final RbdImage image = rbd.open(snapshotDisk.getName(), snapshotName);
          final File fh = new File(snapshotDestPath);
          try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(fh)); ) {
            final int chunkSize = 4194304;
            long offset = 0;
            s_logger.debug(
                "Backuping up RBD snapshot " + snapshotName + " to  " + snapshotDestPath);
            while (true) {
              final byte[] buf = new byte[chunkSize];
              final int bytes = image.read(offset, buf, chunkSize);
              if (bytes <= 0) {
                break;
              }
              bos.write(buf, 0, bytes);
              offset += bytes;
            }
            s_logger.debug(
                "Completed backing up RBD snapshot "
                    + snapshotName
                    + " to  "
                    + snapshotDestPath
                    + ". Bytes written: "
                    + offset);
          } catch (final IOException ex) {
            s_logger.error("BackupSnapshotAnswer:Exception:" + ex.getMessage());
          }
          r.ioCtxDestroy(io);
        } catch (final RadosException e) {
          s_logger.error("A RADOS operation failed. The error was: " + e.getMessage());
          return new BackupSnapshotAnswer(command, false, e.toString(), null, true);
        } catch (final RbdException e) {
          s_logger.error(
              "A RBD operation on "
                  + snapshotDisk.getName()
                  + " failed. The error was: "
                  + e.getMessage());
          return new BackupSnapshotAnswer(command, false, e.toString(), null, true);
        }
      } else {
        final Script scriptCommand = new Script(manageSnapshotPath, cmdsTimeout, s_logger);
        scriptCommand.add("-b", snapshotDisk.getPath());
        scriptCommand.add("-n", snapshotName);
        scriptCommand.add("-p", snapshotDestPath);
        scriptCommand.add("-t", snapshotName);
        final String result = scriptCommand.execute();

        if (result != null) {
          s_logger.debug("Failed to backup snaptshot: " + result);
          return new BackupSnapshotAnswer(command, false, result, null, true);
        }
      }
      /* Delete the snapshot on primary */

      DomainState state = null;
      Domain vm = null;
      if (vmName != null) {
        try {
          vm = libvirtComputingResource.getDomain(conn, command.getVmName());
          state = vm.getInfo().state;
        } catch (final LibvirtException e) {
          s_logger.trace("Ignoring libvirt error.", e);
        }
      }

      final KVMStoragePool primaryStorage =
          storagePoolMgr.getStoragePool(command.getPool().getType(), command.getPool().getUuid());

      if (state == DomainState.VIR_DOMAIN_RUNNING && !primaryStorage.isExternalSnapshot()) {
        final MessageFormat snapshotXML =
            new MessageFormat(
                "   <domainsnapshot>"
                    + "       <name>{0}</name>"
                    + "          <domain>"
                    + "            <uuid>{1}</uuid>"
                    + "        </domain>"
                    + "    </domainsnapshot>");

        final String vmUuid = vm.getUUIDString();
        final Object[] args = new Object[] {snapshotName, vmUuid};
        final String snapshot = snapshotXML.format(args);
        s_logger.debug(snapshot);
        final DomainSnapshot snap = vm.snapshotLookupByName(snapshotName);
        if (snap != null) {
          snap.delete(0);
        } else {
          throw new CloudRuntimeException("Unable to find vm snapshot with name -" + snapshotName);
        }

        /*
         * libvirt on RHEL6 doesn't handle resume event emitted from
         * qemu
         */
        vm = libvirtComputingResource.getDomain(conn, command.getVmName());
        state = vm.getInfo().state;
        if (state == DomainState.VIR_DOMAIN_PAUSED) {
          vm.resume();
        }
      } else {
        final Script scriptCommand = new Script(manageSnapshotPath, cmdsTimeout, s_logger);
        scriptCommand.add("-d", snapshotDisk.getPath());
        scriptCommand.add("-n", snapshotName);
        final String result = scriptCommand.execute();
        if (result != null) {
          s_logger.debug("Failed to backup snapshot: " + result);
          return new BackupSnapshotAnswer(
              command, false, "Failed to backup snapshot: " + result, null, true);
        }
      }
    } catch (final LibvirtException e) {
      return new BackupSnapshotAnswer(command, false, e.toString(), null, true);
    } catch (final CloudRuntimeException e) {
      return new BackupSnapshotAnswer(command, false, e.toString(), null, true);
    } finally {
      if (secondaryStoragePool != null) {
        storagePoolMgr.deleteStoragePool(
            secondaryStoragePool.getType(), secondaryStoragePool.getUuid());
      }
    }
    return new BackupSnapshotAnswer(
        command, true, null, snapshotRelPath + File.separator + snapshotName, true);
  }