Java gRPC：从客户端到服务器的异常

Question

有可能从客户端向服务器抛出异常吗？我们有一个从服务器到客户端的开放流：

rpc addStream(Request) returns (stream StreamMessage) {}     

当我尝试这样的事情时：

throw Status.INTERNAL.withDescription(e.getMessage()).withCause(e.getCause()).asRuntimeException();

我在客户端的StreamObserver.on错误中获得了异常，但在服务器端没有异常。

Answer 1

服务器可以用存根应用编程接口公开的“状态”来响应。然而，客户端只能“取消”RPC。服务器不知道取消的来源；可能是因为客户端取消了，也可能是传输控制协议中断了。

在客户端流式或双流式调用中，客户端可以通过调用observer.onError（）来取消（而不必调用onFuleted（））。但是，如果客户端调用了onFuleted（）或者RPC有一个一元请求，那么您需要使用ClientCallStream观察者或Context：

java prettyprint-override">stub.someRpc(request, new ClientResponseObserver<Request, Response>() {
  private ClientCallStreamObserver<Request> requestStream;

  @Override public void beforeStart(ClientCallStreamObserver<Request> requestStream) {
    this.requestStream = requestStream;
  }
  ...
});

// And then where you want to cancel

// RequestStream is non-thread-safe. For unary requests, wait until
// stub.someRpc() returns, since it uses the stream internally.
// The string is not sent to the server. It is just "echoed"
// back to the client's `onError()` to make clear that the
// cancellation was locally caused.
requestStream.cancel("some message for yourself", null);


// For thread-safe cancellation (e.g., for client-streaming)
CancellableContext ctx = Context.current().withCancellation();
StreamObserver requestObserver = ctx.call(() ->
  stub.someRpc(new StreamObserver<Response>() {
    @Override public void onCompleted() {
      // The ctx must be closed when done, to avoid leaks
      ctx.cancel(null);
    }

    @Override public void onError() {
      ctx.cancel(null);
    }
  }));

// The place you want to cancel
ctx.cancel(ex);