Client Streaming API: Server-Side Implementation

Client streaming APIs in gRPC allow the client to send a stream of data to the server in response to a single request. On the server side, you need to handle the incoming stream of data and process it appropriately.

Key Components of Server-Side Implementation

• Server: The server handles the request and receives a stream of responses from the client.
• Client: The client sends a single request to the server and sends a stream of responses.
• StreamObserver: The server uses a StreamObserver to receive responses from the client.

Implementing a Server for Client Streaming APIs

1. Define the Service and Messages: Create a .proto file to define the service and message definitions.
2. Generate Server Code: Use the protoc compiler to generate server code from the .proto file.
3. Implement the Service: Override the client streaming method in your service implementation.
4. Receive Requests: Use the StreamObserver interface to receive requests from the client.

Example

Protocol Buffers

syntax = "proto3";

service UploadService {
  rpc UploadFile(stream UploadRequest) returns (UploadResponse) {}
}

message UploadRequest {
  bytes data = 1;
}

message UploadResponse {
  bool success = 1;
  string message = 2;
}

Java

public class UploadServiceImpl extends UploadServiceGrpc.UploadServiceImplBase {
    @Override
    public StreamObserver<UploadRequest> uploadFile(StreamObserver<UploadResponse>    responseObserver) {
        return new StreamObserver<UploadRequest>() {
            private long totalBytes = 0;

            @Override
            public void onNext(UploadRequest request) {
                // Process the uploaded data
                totalBytes += request.getData().size();
                // ...
            }

            @Override
            public void onError(Throwable t) {
                // Handle errors
                System.err.println("Error: " + t.getMessage());
                responseObserver.onError(t);
            }

            @Override
            public void onCompleted() {
                // Process the completed upload
                UploadResponse response = UploadResponse.newBuilder().setSuccess(true).setMessage("Upload successful").build();
                responseObserver.onNext(response);
                responseObserver.onCompleted();
            }
        };
    }
}

By following these guidelines, you can effectively implement the server-side of a client streaming API in gRPC and handle the stream of data from the client.