python - gRPC:Rendezvous 终止(StatusCode.INTERNAL，收到 RST_STREAM，错误代码为 2)

Question

我正在用 python 实现 gRPC 客户端和服务器。服务器成功接收来自客户端的数据，但客户端收到返回“RST_STREAM with error code 2”。

它实际上意味着什么？我该如何解决它？

这是我的原型(prototype)文件:

service MyApi {
    rpc SelectModelForDataset (Dataset) returns (SelectedModel) {
    }
}
message Dataset {
    // ...
}
message SelectedModel {
    // ...
}

我的服务实现如下所示:

class MyApiServicer(my_api_pb2_grpc.MyApiServicer):
def SelectModelForDataset(self, request, context):
    print("Processing started.")
    selectedModel = ModelSelectionModule.run(request, context)  
    print("Processing Completed.")
    return selectedModel

我使用以下代码启动服务器:

import grpc
from concurrent import futures
#...
server = grpc.server(futures.ThreadPoolExecutor(max_workers=100))
my_api_pb2_grpc.add_MyApiServicer_to_server(MyApiServicer(), server)
server.add_insecure_port('[::]:50051')
server.start()

我的客户看起来像这样:

channel = grpc.insecure_channel(target='localhost:50051')
stub = my_api_pb2_grpc.MyApiStub(channel)
dataset = my_api_pb2.Dataset() 
# fill the object ...
model = stub.SelectModelForDataset(dataset)  # call server

客户端发出调用后，服务器开始处理直到完成(大约需要一分钟)，但客户端立即返回并出现以下错误:

Traceback (most recent call last):                                                                   
File "Client.py", line 32, in <module>                                                               
    run()                                                                                            
File "Client.py", line 26, in run                                                                    
    model = stub.SelectModelForDataset(dataset)  # call server                                       
File "/usr/local/lib/python3.5/dist-packages/grpc/_channel.py", line 484, in __call__
    return _end_unary_response_blocking(state, call, False, deadline)                                
File "/usr/local/lib/python3.5/dist-packages/grpc/_channel.py", line 434, in _end_unary_response_blocking                                                                                               
    raise _Rendezvous(state, None, None, deadline)                                                 
grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with (StatusCode.INTERNAL, Received RST_STREAM with error code 2)>

如果我异步执行请求并等待将来，

model_future = stub.SelectModelForDataset.future(dataset)  # call server
model = model_future.result()

客户端等待直到完成，但之后仍然返回错误:

Traceback (most recent call last):                                                                   
File "AsyncClient.py", line 35, in <module>                                                          
    run()                                                                                            
File "AsyncClient.py", line 29, in run                                                               
    model = model_future.result()                                                                    
File "/usr/local/lib/python3.5/dist-packages/grpc/_channel.py", line 276, in result                  
    raise self                                                                                     
grpc._channel._Rendezvous: <_Rendezvous of RPC that terminated with (StatusCode.INTERNAL, Received RST_STREAM with error code 2)>

UPD:启用跟踪GRPC_TRACE=all后，我发现了以下内容:

客户，请求后立即:

E0109 17:59:42.248727600    1981 channel_connectivity.cc:126] watch_completion_error: {"created":"@1515520782.248638500","description":"GOAWAY received","file":"src/core/ext/transport/chttp2/transport/chttp2_transport.cc","file_line":1137,"http2_error":0,"raw_bytes":"Server shutdown"}            
E0109 17:59:42.451048100    1979 channel_connectivity.cc:126] watch_completion_error: "Cancelled"  
E0109 17:59:42.451160000    1979 completion_queue.cc:659]    Operation failed: tag=0x7f6e5cd1caf8, error={"created":"@1515520782.451034300","description":"Timed out waiting for connection state change","file":"src/core/ext/filters/client_channel/channel_connectivity.cc","file_line":133}
...(last two messages keep repeating 5 times every second)

服务器:

E0109 17:59:42.248201000    1985 completion_queue.cc:659]    Operation failed: tag=0x7f3f74febee8, error={"created":"@1515520782.248170000","description":"Server Shutdown","file":"src/core/lib/surface/server.cc","file_line":1249}                                                                    
E0109 17:59:42.248541100    1975 tcp_server_posix.cc:231]    Failed accept4: Invalid argument                                                                             
E0109 17:59:47.362868700    1994 completion_queue.cc:659]    Operation failed: tag=0x7f3f74febee8, error={"created":"@1515520787.362853500","description":"Server Shutdown","file":"src/core/lib/surface/server.cc","file_line":1249}                                                                                                                                             
E0109 17:59:52.430612500    2000 completion_queue.cc:659]    Operation failed: tag=0x7f3f74febee8, error={"created":"@1515520792.430598800","description":"Server Shutdown","file":"src/core/lib/surface/server.cc","file_line":1249}
... (last message kept repeating every few seconds)                                                             

UPD2:

我的 Server.py 文件的完整内容:

import ModelSelectionModule
import my_api_pb2_grpc
import my_api_pb2
import grpc
from concurrent import futures
import time

class MyApiServicer(my_api_pb2_grpc.MyApiServicer):
    def SelectModelForDataset(self, request, context):
        print("Processing started.")
        selectedModel = ModelSelectionModule.run(request, context)
        print("Processing Completed.")
        return selectedModel


# TODO(shalamov): what is the best way to run a python server?
def serve():
    server = grpc.server(futures.ThreadPoolExecutor(max_workers=100))
    my_api_pb2_grpc.add_MyApiServicer_to_server(MyApiServicer(), server)
    server.add_insecure_port('[::]:50051')
    server.start()

    print("gRPC server started\n")
    try:
        while True:
            time.sleep(24 * 60 * 60)  # run for 24h
    except KeyboardInterrupt:
        server.stop(0)


if __name__ == '__main__':
    serve()

UPD3:似乎是 ModelSelectionModule.run 导致了问题。我尝试将其隔离到一个单独的线程中，但没有帮助。 selectedModel 最终被计算出来，但此时客户端已经消失了。 如何防止此调用干扰 grpc？

pool = ThreadPool(processes=1)
async_result = pool.apply_async(ModelSelectionModule.run(request, context))
selectedModel = async_result.get()

该调用相当复杂，它会生成并加入许多线程，调用不同的库，例如 scikit-learn 和 smac 等。如果我把所有内容都贴在这里就太多了。

在调试时，我发现在客户端发出请求后，服务器保持 2 个连接打开(fd 3 和 fd 8)。如果我手动关闭fd 8或向其写入一些字节，我在客户端中看到的错误将变为Streamremoved(而不是Received RST_STREAM with error code 2)。似乎套接字(fd 8)以某种方式被子进程损坏。 这怎么可能？如何保护套接字不被子进程访问？

Answer 1

这是在进程处理程序中使用 fork() 的结果。 gRPC Python 不支持此用例。