# Buggy code
def _blocking_send(
    self, req: ray_client_pb2.DataRequest
) -> ray_client_pb2.DataResponse:
    req_id = self._next_id()
    req.req_id = req_id
    self.request_queue.put(req)
    data = None
    with self.cv:
        self.cv.wait_for(lambda: req_id in self.ready_data)
        data = self.ready_data[req_id]
        del self.ready_data[req_id]
    return data


# Traceback (debug_error)
Got Error from data channel -- shutting down: <_MultiThreadedRendezvous of RPC that terminated with:
status = StatusCode.UNAVAILABLE
details = "Received http2 header with status: 502"
debug_error_string = "{"created":"@1610421939.184399675","description":"Received http2 :status header with non-200 OK status","file":"src/core/ext/filters/http/client/http_client_filter.cc","file_line":129,"grpc_message":"Received http2 header with status: 502","grpc_status":14,"value":"502"}"

Got Error from logger channel -- shutting down: <_MultiThreadedRendezvous of RPC that terminated with:
status = StatusCode.UNAVAILABLE
details = "Received http2 header with status: 502"
debug_error_string = "{"created":"@1610421939.184408826","description":"Received http2 :status header with non-200 OK status","file":"src/core/ext/filters/http/client/http_client_filter.cc","file_line":129,"grpc_message":"Received http2 header with status: 502","grpc_status":14,"value":"502"}"

Exception in thread Thread-1:
Traceback (most recent call last):
File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
self.run()
File "/usr/lib/python3.6/threading.py", line 864, in run
self._target(*self._args, **self._kwargs)
File "/home/eric/Desktop/ray/python/ray/util/client/dataclient.py", line 76, in _data_main
raise e
File "/home/eric/Desktop/ray/python/ray/util/client/dataclient.py", line 61, in _data_main
for response in resp_stream:
File "/home/eric/.local/lib/python3.6/site-packages/grpc/_channel.py", line 416, in __next__
return self._next()
File "/home/eric/.local/lib/python3.6/site-packages/grpc/_channel.py", line 706, in _next
raise self
grpc._channel._MultiThreadedRendezvous: <_MultiThreadedRendezvous of RPC that terminated with:
status = StatusCode.UNAVAILABLE
details = "Received http2 header with status: 502"
debug_error_string = "{"created":"@1610421939.184399675","description":"Received http2 :status header with non-200 OK status","file":"src/core/ext/filters/http/client/http_client_filter.cc","file_line":129,"grpc_message":"Received http2 header with status: 502","grpc_status":14,"value":"502"}"


Exception in thread Thread-2:
Traceback (most recent call last):
File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
self.run()
File "/usr/lib/python3.6/threading.py", line 864, in run
self._target(*self._args, **self._kwargs)
File "/home/eric/Desktop/ray/python/ray/util/client/logsclient.py", line 51, in _log_main
raise e
File "/home/eric/Desktop/ray/python/ray/util/client/logsclient.py", line 42, in _log_main
for record in log_stream:
File "/home/eric/.local/lib/python3.6/site-packages/grpc/_channel.py", line 416, in __next__
return self._next()
File "/home/eric/.local/lib/python3.6/site-packages/grpc/_channel.py", line 706, in _next
raise self
grpc._channel._MultiThreadedRendezvous: <_MultiThreadedRendezvous of RPC that terminated with:
status = StatusCode.UNAVAILABLE
details = "Received http2 header with status: 502"
debug_error_string = "{"created":"@1610421939.184408826","description":"Received http2 :status header with non-200 OK status","file":"src/core/ext/filters/http/client/http_client_filter.cc","file_line":129,"grpc_message":"Received http2 header with status: 502","grpc_status":14,"value":"502"}"


# Fixed code
def _blocking_send(
    self, req: ray_client_pb2.DataRequest
) -> ray_client_pb2.DataResponse:
    req_id = self._next_id()
    req.req_id = req_id
    self.request_queue.put(req)
    data = None
    with self.cv:
        self.cv.wait_for(lambda: req_id in self.ready_data or self._in_shutdown)
        if self._in_shutdown:
            raise ConnectionError(
                f"cannot send request {req}: data channel shutting down"
            )
        data = self.ready_data[req_id]
        del self.ready_data[req_id]
    return data