com.google.api.gax.rpc

Interface OperationFuture<ResponseT,MetadataT,OperationT>

All Superinterfaces:

com.google.api.core.ApiFuture<ResponseT>, Future<ResponseT>

All Known Implementing Classes:

FakeOperationApi.FakeOperationFuture

@BetaApi
public interface OperationFuture<ResponseT,MetadataT,OperationT>
extends com.google.api.core.ApiFuture<ResponseT>

An ApiFuture which tracks polling of a service, typically started by OperationCallable.futureCall(Object, ApiCallContext). The polling is done periodically, based on the TimedRetryAlgorithm specified in OperationCallSettings provided during creation of the corresponding OperationCallable.

Implementations are expected to be thread-safe.

Method Summary

Modifier and Type	Method and Description
com.google.api.core.ApiFuture<OperationT>	getInitialFuture() Returns the OperationT future of the initial request which started this OperationFuture.
com.google.api.core.ApiFuture<MetadataT>	getMetadata() Gets the metadata of the operation tracked by this OperationFuture.
String	getName() Returns the value of the name of the operation from the initial operation object returned from the initial call to start the operation.
com.google.api.core.ApiFuture<MetadataT>	peekMetadata() Peeks at the metadata of the operation tracked by this OperationFuture.

Methods inherited from interface com.google.api.core.ApiFuture

addListener

Methods inherited from interface java.util.concurrent.Future

cancel, get, get, isCancelled, isDone

Method Detail

getName

String getName()
        throws InterruptedException,
               ExecutionException

Returns the value of the name of the operation from the initial operation object returned from the initial call to start the operation. Blocks if the initial call to start the operation hasn't returned yet.

Throws:

InterruptedException

ExecutionException

getInitialFuture

com.google.api.core.ApiFuture<OperationT> getInitialFuture()

Returns the OperationT future of the initial request which started this OperationFuture.

peekMetadata

com.google.api.core.ApiFuture<MetadataT> peekMetadata()

Peeks at the metadata of the operation tracked by this OperationFuture. If the initial future hasn't completed yet this method returns null, otherwise it returns the latest metadata returned from the server (i.e. either initial call metadata or the metadata received from the latest completed poll iteration).

If not null, the returned result is guaranteed to be an already completed future, so Future.isDone() will always be true and Future.get() will always be non-blocking.

Note, some APIs may return null in metadata response message. In such cases this method may return a non-null future whose get() method will return null. This behavior is API specific an should be considered a valid case, which indicates that the recent poll request has completed, but no specific metadata was provided by the server (i.e. most probably providing metadata for an intermediate result is not supported by the server).

This method should be used to check operation progress without blocking current thread. Since this method returns metadata from the latest completed poll, it is potentially slightly stale compared to the most recent data. To get the most recent data and/or get notified when the current scheduled poll request completes use the getMetadata() method instead.

If this operation future is completed, this method always returns the metadata from the last poll request (which completed the operation future).

If this operation future failed, this method may (depending on the failure type) return a non-failing future, representing the metadata from the last poll request (which failed the operation future).

If this operation future was cancelled, this method returns a canceled metatata future as well.

In general this method behaves similarly to RetryingFuture.peekAttemptResult().

getMetadata

com.google.api.core.ApiFuture<MetadataT> getMetadata()

Gets the metadata of the operation tracked by this OperationFuture. This method returns the current poll metadata result (or the initial call metadata if it hasn't completed yet). The returned future completes once the current scheduled poll request (or the initial request if it hasn't completed yet) is executed and response is received from the server. The time when the polling request is executed is determined by the underlying polling algorithm.

Adding direct executor (same thread) callbacks to the future returned by this method is strongly not recommended, since the future is resolved under retrying future's internal lock and may affect the operation polling process. Adding separate thread callbacks is ok.

Note, some APIs may return null in metadata response message. In such cases this method may return a non-null future whose get() method will return null. This behavior is API specific an should be considered a valid case, which indicates that the recent poll request has completed, but no specific metadata was provided by the server. (i.e. most probably providing metadata for an intermediate result is not supported by the server).

In most cases this method returns a future which is not completed yet, so calling Future.get() is a potentially blocking operation. To get metadata without blocking the current thread use the peekMetadata() method instead.

If this operation future is completed, this method always returns the metadata from the last poll request (which completed the operation future).

If this operation future failed, this method may (depending on the failure type) return a non-failing future, representing the metadata from the last poll request (which failed the operation future).

If this operation future was cancelled, this method returns a canceled metatata future as well.

In general this method behaves similarly to RetryingFuture.getAttemptResult().