gRPC future callback got exception:StatusRuntimeException: CANCELLED

Question

io.grpc.StatusRuntimeException: CANCELLED
    at io.grpc.Status.asRuntimeException(Status.java:539)
    at io.grpc.stub.ClientCalls$UnaryStreamToFuture.onClose(ClientCalls.java:439)
    at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:422)
    at io.grpc.internal.ClientCallImpl.access$100(ClientCallImpl.java:74)
    at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.close(ClientCallImpl.java:508)
    at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.access$700(ClientCallImpl.java:425)
    at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:540)
    at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:52)
    at io.grpc.internal.SerializeReentrantCallsDirectExecutor.execute(SerializeReentrantCallsDirectExecutor.java:64)
    at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.closed(ClientCallImpl.java:544)
    at io.grpc.internal.AbstractClientStream2$TransportState.closeListener(AbstractClientStream2.java:307)
    at io.grpc.internal.AbstractClientStream2$TransportState.transportReportStatus(AbstractClientStream2.java:287)
    at io.grpc.netty.NettyClientHandler.cancelStream(NettyClientHandler.java:455)
    at io.grpc.netty.NettyClientHandler.write(NettyClientHandler.java:231)
    at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:739)
    at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:731)
    at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:817)
    at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:724)
    at io.netty.channel.DefaultChannelPipeline.write(DefaultChannelPipeline.java:1022)
    at io.netty.channel.AbstractChannel.write(AbstractChannel.java:291)
    at io.grpc.netty.WriteQueue.flush(WriteQueue.java:124)
    at io.grpc.netty.WriteQueue.access$000(WriteQueue.java:46)
    at io.grpc.netty.WriteQueue$1.run(WriteQueue.java:58)
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:403)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:445)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
    at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:144)
    at java.lang.Thread.run(Thread.java:745)

I got an exception as above when i call another grpc service in a grpc server handle process with future & callback.

My code like this:

handle(){

....

***FutureClient futureClient = ...
ListenableFuture<***> future = futureClient.call(...);
Futures.addCallback(future, new FutureCallback<>() {...});

...

}

The access was canceled when the process handle() completed.

How can I resolve the problem?

Answer 1

Outgoing RPCs from a server are implicitly tied to the incoming request that triggered them, via io.grpc.Context. If you are doing an RPC that proceeds even after the incoming RPC completed you should use context.fork():

Context forked = Context.current().fork();
Context old = forked.attach();
try {
  // RPCs at this point can continue after the incoming RPC completes
  futureClient.call(...);
} finally {
  forked.detach(old);
}

Context.run(Runnable) is also a convenient alternative to using attach/detach directly.