@SuppressWarnings("unchecked")
 @Override
 public void allocate(Allocation allocInfo) throws Exception {
   RestrictedTypes.allocateNamedUnitlessResources(
       allocInfo.getAllocationTokens().size(),
       allocInfo.getVmType().allocator(),
       (Predicate) Predicates.alwaysTrue());
 }
    @Override
    public boolean apply(Allocation allocInfo)
        throws MetadataException, AuthException, VerificationException {
      RunInstancesType msg = allocInfo.getRequest();
      String imageId = msg.getImageId();
      VmType vmType = allocInfo.getVmType();
      try {
        BootableSet bootSet = Emis.newBootableSet(imageId);
        allocInfo.setBootableSet(bootSet);

        // Add (1024L * 1024L * 10) to handle NTFS min requirements.
        if (!bootSet.isBlockStorage()) {
          if (Platform.windows.equals(bootSet.getMachine().getPlatform())
              && bootSet.getMachine().getImageSizeBytes()
                  > ((1024L * 1024L * 1024L * vmType.getDisk()) + (1024L * 1024L * 10))) {
            throw new ImageInstanceTypeVerificationException(
                "Unable to run instance "
                    + bootSet.getMachine().getDisplayName()
                    + " in which the size "
                    + bootSet.getMachine().getImageSizeBytes()
                    + " bytes of the instance is greater than the vmType "
                    + vmType.getDisplayName()
                    + " size "
                    + vmType.getDisk()
                    + " GB.");
          } else if (bootSet.getMachine().getImageSizeBytes()
              > ((1024L * 1024L * 1024L * vmType.getDisk()))) {
            throw new ImageInstanceTypeVerificationException(
                "Unable to run instance "
                    + bootSet.getMachine().getDisplayName()
                    + " in which the size "
                    + bootSet.getMachine().getImageSizeBytes()
                    + " bytes of the instance is greater than the vmType "
                    + vmType.getDisplayName()
                    + " size "
                    + vmType.getDisk()
                    + " GB.");
          }
        }
      } catch (VerificationException e) {
        throw e;
      } catch (MetadataException ex) {
        LOG.error(ex);
        throw ex;
      } catch (RuntimeException ex) {
        LOG.error(ex);
        throw new VerificationException(
            "Failed to verify references for request: "
                + msg.toSimpleString()
                + " because of: "
                + ex.getMessage(),
            ex);
      }
      return true;
    }
    @Override
    public void allocate(Allocation allocInfo) throws Exception {
      Partition reqPartition = allocInfo.getPartition();
      String zoneName = reqPartition.getName();
      String vmTypeName = allocInfo.getVmType().getName();

      /* Validate min and max amount */
      final int minAmount = allocInfo.getMinCount();
      final int maxAmount = allocInfo.getMaxCount();
      if (minAmount > maxAmount)
        throw new RuntimeException(
            "Maximum instance count must not be smaller than minimum instance count");

      /* Retrieve our context and list of clusters associated with this zone */
      List<Cluster> authorizedClusters = this.doPrivilegedLookup(zoneName, vmTypeName);

      int remaining = maxAmount;
      int allocated = 0;
      int available;

      LOG.info(
          "Found authorized clusters: "
              + Iterables.transform(authorizedClusters, HasName.GET_NAME));

      /* Do we have any VM available throughout our clusters? */
      if ((available = checkAvailability(vmTypeName, authorizedClusters)) < minAmount) {
        throw new NotEnoughResourcesException(
            "Not enough resources ("
                + available
                + " in "
                + zoneName
                + " < "
                + minAmount
                + "): vm instances.");
      } else {
        for (Cluster cluster : authorizedClusters) {
          if (remaining <= 0) {
            break;
          } else {
            ResourceState state = cluster.getNodeState();
            Partition partition = cluster.getConfiguration().lookupPartition();

            /* Has a partition been set if the AZ was not specified? */
            if (allocInfo.getPartition().equals(Partition.DEFAULT)) {
              /*
               * Ok, do we have enough slots in this partition to support our request? We should have at least
               * the minimum. The list is sorted in order of resource availability from the cluster with the most
               * available to the cluster with the least amount available. This is why we don't check against the
               * maxAmount value since its a best effort at this point. If we select the partition here and we
               * can't fit maxAmount, based on the sorting order, the next partition will not fit maxAmount anyway.
               */
              int zoneAvailable = checkZoneAvailability(vmTypeName, partition, authorizedClusters);
              if (zoneAvailable < minAmount) continue;

              /* Lets use this partition */
              allocInfo.setPartition(partition);
            } else if (!allocInfo.getPartition().equals(partition)) {
              /* We should only pick clusters that are part of the selected AZ */
              continue;
            }

            if (allocInfo.getBootSet().getMachine() instanceof BlockStorageImageInfo) {
              try {
                Topology.lookup(Storage.class, partition);
              } catch (Exception ex) {
                allocInfo.abort();
                allocInfo.setPartition(reqPartition);
                throw new NotEnoughResourcesException(
                    "Not enough resources: Cannot run EBS instances in partition w/o a storage controller: "
                        + ex.getMessage(),
                    ex);
              }
            }

            try {
              int tryAmount =
                  (remaining > state.getAvailability(vmTypeName).getAvailable())
                      ? state.getAvailability(vmTypeName).getAvailable()
                      : remaining;

              List<ResourceToken> tokens =
                  this.requestResourceToken(allocInfo, tryAmount, maxAmount);
              remaining -= tokens.size();
              allocated += tokens.size();
            } catch (Exception t) {
              LOG.error(t);
              Logs.extreme().error(t, t);

              allocInfo.abort();
              allocInfo.setPartition(reqPartition);

              /* if we still have some allocation remaining AND no more resources are available */
              if (((available = checkZoneAvailability(vmTypeName, partition, authorizedClusters))
                      < remaining)
                  && (remaining > 0)) {
                throw new NotEnoughResourcesException(
                    "Not enough resources ("
                        + available
                        + " in "
                        + zoneName
                        + " < "
                        + minAmount
                        + "): vm instances.",
                    t);
              } else {
                throw new NotEnoughResourcesException(t.getMessage(), t);
              }
            }
          }
        }

        /* Were we able to meet our minimum requirements? */
        if ((allocated < minAmount) && (remaining > 0)) {
          allocInfo.abort();
          allocInfo.setPartition(reqPartition);

          if (reqPartition.equals(Partition.DEFAULT)) {
            throw new NotEnoughResourcesException(
                "Not enough resources available in all zone for " + minAmount + "): vm instances.");
          } else {
            available = checkZoneAvailability(vmTypeName, reqPartition, authorizedClusters);
            throw new NotEnoughResourcesException(
                "Not enough resources ("
                    + available
                    + " in "
                    + zoneName
                    + " < "
                    + minAmount
                    + "): vm instances.");
          }
        }
      }
    }
    private List<ResourceToken> requestResourceToken(
        final Allocation allocInfo, final int tryAmount, final int maxAmount) throws Exception {
      ServiceConfiguration config =
          Topology.lookup(ClusterController.class, allocInfo.getPartition());
      Cluster cluster = Clusters.lookup(config);
      /**
       * TODO:GRZE: this is the call path which needs to trigger gating.
       * It shouldn't be handled directly here, but instead be handled in {@link ResourceState#requestResourceAllocation().
       *
       */
      if (cluster.getGateLock().readLock().tryLock(60, TimeUnit.SECONDS)) {
        try {
          final ResourceState state = cluster.getNodeState();
          /**
           * NOTE: If the defined instance type has an ordering conflict w/ some other type then it
           * isn't safe to service TWO requests which use differing types during the same resource
           * refresh duty cycle. This determines whether or not an asynchronous allocation is safe
           * to do for the request instance type or whether a synchronous resource availability
           * refresh is needed.
           */
          boolean unorderedType = VmTypes.isUnorderedType(allocInfo.getVmType());
          boolean forceResourceRefresh = state.hasUnorderedTokens() || unorderedType;
          /**
           * GRZE: if the vm type is not "nicely" ordered then we force a refresh of the actual
           * cluster state. Note: we already hold the cluster gating lock here so this update will
           * be mutual exclusive wrt both resource allocations and cluster state updates.
           */
          if (forceResourceRefresh) {
            cluster.refreshResources();
          }
          final List<ResourceToken> tokens =
              state.requestResourceAllocation(allocInfo, tryAmount, maxAmount);
          final Iterator<ResourceToken> tokenIterator = tokens.iterator();
          try {
            final Supplier<ResourceToken> allocator =
                new Supplier<ResourceToken>() {
                  @Override
                  public ResourceToken get() {
                    final ResourceToken ret = tokenIterator.next();
                    allocInfo.getAllocationTokens().add(ret);
                    return ret;
                  }
                };

            RestrictedTypes.allocateUnitlessResources(tokens.size(), allocator);
          } finally {
            // release any tokens that were not allocated
            Iterators.all(
                tokenIterator,
                new Predicate<ResourceToken>() {
                  @Override
                  public boolean apply(final ResourceToken resourceToken) {
                    state.releaseToken(resourceToken);
                    return true;
                  }
                });
          }
          return allocInfo.getAllocationTokens();
        } finally {
          cluster.getGateLock().readLock().unlock();
        }
      } else {
        throw new ServiceStateException(
            "Failed to allocate resources in the zone "
                + cluster.getPartition()
                + ", it is currently locked for maintenance.");
      }
    }