背景

用Java Springboot起一个grpc服务，参照官方示例，但是启动后用Postman或者其他客户端调用时，不论调用什么方法，都是报 12 UNIMPLEMENTED。而且服务端日志里显示Stream was terminated by error, no further calls are allowed。

报错信息如下：

2023-07-07 21:55:28.433 [grpc-default-executor-0] ERROR io.grpc.internal.SerializingExecutor- Exception while executing runnable io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed@30f27e20
java.lang.IllegalStateException: Stream was terminated by error, no further calls are allowed
    at com.google.common.base.Preconditions.checkState(Preconditions.java:511)
    at io.grpc.stub.ServerCalls$ServerCallStreamObserverImpl.onNext(ServerCalls.java:359)
    at com.example.app.report.service.grpc.ReportServiceImpl.reportCompletion(ReportServiceImpl.java:16)
    at com.example.app.report.proto.generated.ReportServiceGrpc$MethodHandlers.invoke(ReportServiceGrpc.java:312)
    at io.grpc.stub.ServerCalls$UnaryServerCallHandler$UnaryServerCallListener.onHalfClose(ServerCalls.java:182)
    at io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.halfClosed(ServerCallImpl.java:331)
    at io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed.runInContext(ServerImpl.java:797)
    at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
    at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:123)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:750)

关键代码如下：

public class ReportServiceImpl extends ReportServiceGrpc.ReportServiceImplBase {
    @Override
    public void report(ReportEvent request, StreamObserver<ReportResponse> responseObserver) {
        super.report(request, responseObserver);
        responseObserver.onNext(ReportResponse.newBuilder().setCode(0).build());
        responseObserver.onCompleted();
    }
}

解决过程

在方法中打日志，这个方法确实被调用了。而且开启grpc服务端反射以后，也能读取到这个方法。
反复和官方示例对比，最后发现IDEA自动补全的Override代码里，会自动调用super类的方法。而这个方法，默认就会返回一个Unimplemented响应。

// 生成的reportService.java文件
...
    public void reportCompletion(com.example.app.report.proto.generated.CompletionEvent request,
        io.grpc.stub.StreamObserver<com.example.app.report.proto.generated.ReportResponse> responseObserver) {
      io.grpc.stub.ServerCalls.asyncUnimplementedUnaryCall(getReportCompletionMethod(), responseObserver); // 默认返回未实现响应
    }
...

解决方案

只需要把自动生成的调用super类的方法删掉即解决。

这个错误确实没有什么资料，而且比较低级，在此记录一下。

关键词

Java Springboot Grpc Unimplemented