How to use

SerializableOptional

in

org.apache.flink.types

public static <T extends Serializable> SerializableOptional<T> ofNullable(@Nullable T value) {
  if (value == null) {
    return empty();
  } else {
    return of(value);
  }
}

public static <T extends Serializable> SerializableOptional<T> of(@Nonnull T value) {
  return new SerializableOptional<>(value);
}

/**
 * Fail the specified allocation and release the corresponding slot if we have one.
 * This may triggered by JobManager when some slot allocation failed with rpcTimeout.
 * Or this could be triggered by TaskManager, when it finds out something went wrong with the slot,
 * and decided to take it back.
 *
 * @param allocationID Represents the allocation which should be failed
 * @param cause The cause of the failure
 * @return Optional task executor if it has no more slots registered
 */
@Override
public CompletableFuture<SerializableOptional<ResourceID>> failAllocation(final AllocationID allocationID, final Exception cause) {
  final PendingRequest pendingRequest = pendingRequests.removeKeyB(allocationID);
  if (pendingRequest != null) {
    // request was still pending
    failPendingRequest(pendingRequest, cause);
    return CompletableFuture.completedFuture(SerializableOptional.empty());
  }
  else {
    return tryFailingAllocatedSlot(allocationID, cause);
  }
  // TODO: add some unit tests when the previous two are ready, the allocation may failed at any phase
}

private void internalFailAllocation(AllocationID allocationId, Exception cause) {
  final CompletableFuture<SerializableOptional<ResourceID>> emptyTaskExecutorFuture = slotPoolGateway.failAllocation(allocationId, cause);
  emptyTaskExecutorFuture.thenAcceptAsync(
    resourceIdOptional -> resourceIdOptional.ifPresent(this::releaseEmptyTaskManager),
    getMainThreadExecutor());
}

@Override
public CompletableFuture<SerializableOptional<String>> requestMetricQueryServiceAddress(Time timeout) {
  return CompletableFuture.completedFuture(SerializableOptional.ofNullable(metricQueryServicePath));
}

@Override
public CompletableFuture<Collection<Tuple2<ResourceID, String>>> requestTaskManagerMetricQueryServicePaths(Time timeout) {
  final ArrayList<CompletableFuture<Optional<Tuple2<ResourceID, String>>>> metricQueryServicePathFutures = new ArrayList<>(taskExecutors.size());
  for (Map.Entry<ResourceID, WorkerRegistration<WorkerType>> workerRegistrationEntry : taskExecutors.entrySet()) {
    final ResourceID tmResourceId = workerRegistrationEntry.getKey();
    final WorkerRegistration<WorkerType> workerRegistration = workerRegistrationEntry.getValue();
    final TaskExecutorGateway taskExecutorGateway = workerRegistration.getTaskExecutorGateway();
    final CompletableFuture<Optional<Tuple2<ResourceID, String>>> metricQueryServicePathFuture = taskExecutorGateway
      .requestMetricQueryServiceAddress(timeout)
      .thenApply(optional -> optional.map(path -> Tuple2.of(tmResourceId, path)));
    metricQueryServicePathFutures.add(metricQueryServicePathFuture);
  }
  return FutureUtils.combineAll(metricQueryServicePathFutures).thenApply(
    collection -> collection
      .stream()
      .filter(Optional::isPresent)
      .map(Optional::get)
      .collect(Collectors.toList()));
}

/**
 * Fail the specified allocation and release the corresponding slot if we have one.
 * This may triggered by JobManager when some slot allocation failed with rpcTimeout.
 * Or this could be triggered by TaskManager, when it finds out something went wrong with the slot,
 * and decided to take it back.
 *
 * @param allocationID Represents the allocation which should be failed
 * @param cause The cause of the failure
 * @return Optional task executor if it has no more slots registered
 */
@Override
public CompletableFuture<SerializableOptional<ResourceID>> failAllocation(final AllocationID allocationID, final Exception cause) {
  final PendingRequest pendingRequest = pendingRequests.removeKeyB(allocationID);
  if (pendingRequest != null) {
    // request was still pending
    failPendingRequest(pendingRequest, cause);
    return CompletableFuture.completedFuture(SerializableOptional.empty());
  }
  else {
    return tryFailingAllocatedSlot(allocationID, cause);
  }
  // TODO: add some unit tests when the previous two are ready, the allocation may failed at any phase
}

private void internalFailAllocation(AllocationID allocationId, Exception cause) {
  final CompletableFuture<SerializableOptional<ResourceID>> emptyTaskExecutorFuture = slotPoolGateway.failAllocation(allocationId, cause);
  emptyTaskExecutorFuture.thenAcceptAsync(
    resourceIdOptional -> resourceIdOptional.ifPresent(this::releaseEmptyTaskManager),
    getMainThreadExecutor());
}

@Override
public CompletableFuture<SerializableOptional<String>> requestMetricQueryServiceAddress(Time timeout) {
  return CompletableFuture.completedFuture(SerializableOptional.ofNullable(metricQueryServicePath));
}

@Override
public CompletableFuture<Collection<Tuple2<ResourceID, String>>> requestTaskManagerMetricQueryServicePaths(Time timeout) {
  final ArrayList<CompletableFuture<Optional<Tuple2<ResourceID, String>>>> metricQueryServicePathFutures = new ArrayList<>(taskExecutors.size());
  for (Map.Entry<ResourceID, WorkerRegistration<WorkerType>> workerRegistrationEntry : taskExecutors.entrySet()) {
    final ResourceID tmResourceId = workerRegistrationEntry.getKey();
    final WorkerRegistration<WorkerType> workerRegistration = workerRegistrationEntry.getValue();
    final TaskExecutorGateway taskExecutorGateway = workerRegistration.getTaskExecutorGateway();
    final CompletableFuture<Optional<Tuple2<ResourceID, String>>> metricQueryServicePathFuture = taskExecutorGateway
      .requestMetricQueryServiceAddress(timeout)
      .thenApply(optional -> optional.map(path -> Tuple2.of(tmResourceId, path)));
    metricQueryServicePathFutures.add(metricQueryServicePathFuture);
  }
  return FutureUtils.combineAll(metricQueryServicePathFutures).thenApply(
    collection -> collection
      .stream()
      .filter(Optional::isPresent)
      .map(Optional::get)
      .collect(Collectors.toList()));
}

public static <T extends Serializable> SerializableOptional<T> ofNullable(@Nullable T value) {
  if (value == null) {
    return empty();
  } else {
    return of(value);
  }
}

public static <T extends Serializable> SerializableOptional<T> of(@Nonnull T value) {
  return new SerializableOptional<>(value);
}

private CompletableFuture<SerializableOptional<ResourceID>> tryFailingAllocatedSlot(AllocationID allocationID, Exception cause) {
  AllocatedSlot allocatedSlot = availableSlots.tryRemove(allocationID);
  if (allocatedSlot == null) {
    allocatedSlot = allocatedSlots.remove(allocationID);
  }
  if (allocatedSlot != null) {
    log.debug("Failed allocated slot [{}]: {}", allocationID, cause.getMessage());
    // notify TaskExecutor about the failure
    allocatedSlot.getTaskManagerGateway().freeSlot(allocationID, cause, rpcTimeout);
    // release the slot.
    // since it is not in 'allocatedSlots' any more, it will be dropped o return'
    allocatedSlot.releasePayload(cause);
    final ResourceID taskManagerId = allocatedSlot.getTaskManagerId();
    if (!availableSlots.containsTaskManager(taskManagerId) && !allocatedSlots.containResource(taskManagerId)) {
      return CompletableFuture.completedFuture(SerializableOptional.of(taskManagerId));
    }
  }
  return CompletableFuture.completedFuture(SerializableOptional.empty());
}

private CompletableFuture<SerializableOptional<ResourceID>> tryFailingAllocatedSlot(AllocationID allocationID, Exception cause) {
  AllocatedSlot allocatedSlot = availableSlots.tryRemove(allocationID);
  if (allocatedSlot == null) {
    allocatedSlot = allocatedSlots.remove(allocationID);
  }
  if (allocatedSlot != null) {
    log.debug("Failed allocated slot [{}]: {}", allocationID, cause.getMessage());
    // notify TaskExecutor about the failure
    allocatedSlot.getTaskManagerGateway().freeSlot(allocationID, cause, rpcTimeout);
    // release the slot.
    // since it is not in 'allocatedSlots' any more, it will be dropped o return'
    allocatedSlot.releasePayload(cause);
    final ResourceID taskManagerId = allocatedSlot.getTaskManagerId();
    if (!availableSlots.containsTaskManager(taskManagerId) && !allocatedSlots.containResource(taskManagerId)) {
      return CompletableFuture.completedFuture(SerializableOptional.of(taskManagerId));
    }
  }
  return CompletableFuture.completedFuture(SerializableOptional.empty());
}