gRPC:RPC调用上的随机取消异常

Question

我偶尔得到取消错误时，调用gRPC方法。

以下是我的客户端代码（使用grpc java 1.22.0库）：

public class MyClient {
    private static final Logger logger = LoggerFactory.getLogger(MyClient.class);
    private ManagedChannel channel; 
    private FooGrpc.FooStub fooStub;

    private final StreamObserver<Empty> responseObserver = new StreamObserver<>() {
        @Override
        public void onNext(Empty value) {
        }

        @Override
        public void onError(Throwable t) {
            logger.error("Error: ", t);
        }

        @Override
        public void onCompleted() {
        }
    };

    public MyClient() {
        this.channel = NettyChannelBuilder
            .forAddress(host, port)
            .sslContext(GrpcSslContexts.forClient().trustManager(certStream).build())
            .build();
        var pool = Executors.newCachedThreadPool(
                new ThreadFactoryBuilder().setNameFormat("foo-pool-%d").build());
        this.fooStub = FooGrpc.newStub(channel)
                .withExecutor(pool);
    }

    public void callFoo() {
        fooStub.withDeadlineAfter(500L, TimeUnit.MILLISECONDS)
                .myMethod(whatever, responseObserver);
    }
}

当我调用callFoo（）方法时，它通常是有效的。客户端发送消息，服务器接收消息时不会出现问题。

但这个电话偶尔会给我一个错误：

io.grpc.StatusRuntimeException: CANCELLED: io.grpc.Context was cancelled without error
        at io.grpc.Status.asRuntimeException(Status.java:533) ~[handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.stub.ClientCalls$StreamObserverToCallListenerAdapter.onClose(ClientCalls.java:442) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.CensusStatsModule$StatsClientInterceptor$1$1.onClose(CensusStatsModule.java:700) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.PartialForwardingClientCallListener.onClose(PartialForwardingClientCallListener.java:39) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.ForwardingClientCallListener.onClose(ForwardingClientCallListener.java:23) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.ForwardingClientCallListener$SimpleForwardingClientCallListener.onClose(ForwardingClientCallListener.java:40) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.CensusTracingModule$TracingClientInterceptor$1$1.onClose(CensusTracingModule.java:399) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:507) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl.access$300(ClientCallImpl.java:66) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.close(ClientCallImpl.java:627) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.access$700(ClientCallImpl.java:515) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInternal(ClientCallImpl.java:686) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:675) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37) [handler-0.0.1-SNAPSHOT.jar:?]
        at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:123) [handler-0.0.1-SNAPSHOT.jar:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:834) [?:?]

奇怪的是，即使调用在客户端给出了一个错误，服务器还是会收到请求，大部分情况下。但有时服务器会错过它。

它甚至没有超过截止日期\u异常，它只是抛出取消：io。grpc。上下文被取消，没有出现错误。没有提供其他描述，因此我无法理解为什么会发生这种情况。

总结一下：

1. 来自客户端的gRPC呼叫随机给出取消错误

Answer 1

GRPC-java支持自动截止日期和取消传播。当入站RPC导致出站RPC时，这些出站RPC继承入站RPC的截止日期。此外，如果取消入站RPC，则将取消出站RPC。

这是通过io实现的。grpc。上下文。如果你做了一个出站RPC，你想比入站RPC活得更长，你应该使用Context。fork（）。

public void myRpcMethod(Request req, StreamObserver<Response> observer) {
  // ctx has all the values as the current context, but
  // won't be cancelled
  Context ctx = Context.current().fork();
  // Set ctx as the current context within the Runnable
  ctx.run(() -> {
    // Can start asynchronous work here that will not
    // be cancelled when myRpcMethod returns
  });
  observer.onNext(generateReply());
  observer.onCompleted();
}