com.google.cloud.bigtable.gaxx.reframing

Class ReframingResponseObserver<InnerT,OuterT>

java.lang.Object

com.google.api.gax.rpc.StateCheckingResponseObserver<InnerT>

com.google.cloud.bigtable.gaxx.reframing.ReframingResponseObserver<InnerT,OuterT>

All Implemented Interfaces:

ResponseObserver<InnerT>

@InternalApi
public class ReframingResponseObserver<InnerT,OuterT>
extends StateCheckingResponseObserver<InnerT>

Mediates message flow between two ResponseObservers. It is intended for situations when a stream needs to be transformed in such a way where the incoming responses do not map 1:1 to the output responses.

This class manages back pressure between M upstream responses and N downstream responses. It buffers responses when M > N and spools them when M < N. The downstream responses will be delivered via either the upstream thread or the downstream thread that called request(); in either case, the downstream methods will be invoked sequentially. Neither the downstream ResponseObserver nor the Reframer need to be threadsafe.

Expected usage:

  class OuterStreamingCallable extends ServerStreamingCallable<Request, FullResponse> {
    private final ServerStreamingCallable<Request, Chunk> innerCallable;

    OuterStreamingCallable(ServerStreamingCallable<Request, Chunk> innerCallable) {
      this.innerCallable = innerCallable;
    }

    public void call(Request request, ResponseObserver<FullResponse> outerResponseObserver,
 ApiCallContext context) {
      Reframer<Chunk, FullResponse> myReframer = new Reframer<>();
      innerCallable.call(request, new ReframingResponseObserver(myReframer, outerResponseObserver),
 context);
    }
  }
 

Constructor Summary

Constructors

Constructor and Description
ReframingResponseObserver(ResponseObserver<OuterT> observer, Reframer<OuterT,InnerT> reframer)

Method Summary

Modifier and Type	Method and Description
protected void	onCompleteImpl() Process inner/upstream callable's onComplete notification.
protected void	onErrorImpl(Throwable t) Process inner/upstream callable's onError notification.
protected void	onResponseImpl(InnerT response) Accept a new response from inner/upstream callable.
protected void	onStartImpl(StreamController controller) Callback that will be notified when the inner/upstream callable starts.

Methods inherited from class com.google.api.gax.rpc.StateCheckingResponseObserver

onComplete, onError, onResponse, onStart

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ReframingResponseObserver

public ReframingResponseObserver(ResponseObserver<OuterT> observer,
                                 Reframer<OuterT,InnerT> reframer)

Method Detail

onStartImpl

protected void onStartImpl(StreamController controller)

Callback that will be notified when the inner/upstream callable starts. This will in turn notify the outer/downstreamObserver of stream start. Regardless of the outer/downstreamObserver, the upstream controller will be put into manual flow control.

Specified by:

onStartImpl in class StateCheckingResponseObserver<InnerT>

Parameters:

controller - The controller for the upstream stream.

onResponseImpl

protected void onResponseImpl(InnerT response)

Accept a new response from inner/upstream callable. This message will be processed by the Reframer in the delivery loop and the output will be delivered to the downstream ResponseObserver.

If the delivery loop is stopped, this will restart it.

Specified by:

onResponseImpl in class StateCheckingResponseObserver<InnerT>

onErrorImpl

protected void onErrorImpl(Throwable t)

Process inner/upstream callable's onError notification. This will be queued to be delivered after the delegate exhausts its buffers.

If the delivery loop is stopped, this will restart it.

Specified by:

onErrorImpl in class StateCheckingResponseObserver<InnerT>

onCompleteImpl

protected void onCompleteImpl()

Process inner/upstream callable's onComplete notification. This will be queued to be delivered after the delegate exhausts its buffers.

If the delivery loop is stopped, this will restart it.

Specified by:

onCompleteImpl in class StateCheckingResponseObserver<InnerT>