[Core] Stop iteratoring cancelled grpc request streams (#23865) (#27951)

This fixes the below grpc error mentioned in #23865.

grpc._channel._MultiThreadedRendezvous: <_MultiThreadedRendezvous of RPC that terminated with:
        status = StatusCode.UNKNOWN
        details = "Exception iterating requests!"
        debug_error_string = "None"
>
This error happens when proxying the grpc stream to the individual SpecificServer but the incoming grpc stream is already canceled. (https://github.com/grpc/grpc/blob/v1.43.0/src/python/grpcio/grpc/_server.py#L353-L354)

Therefore, just wrap the request_iterator with a new RequestIteratorProxy which will catch the _CANCELLED signal.

Related issue number
#23865

python/ray/tests/test_client_proxy.py

@@ -4,7 +4,8 @@
 import sys
 import time
 from glob import glob
-from unittest.mock import patch
+from unittest.mock import patch, MagicMock
+from itertools import chain
 
 import grpc
 import pytest
@@ -398,6 +399,80 @@ def make_internal_kv_calls():
             make_internal_kv_calls()
 
 
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="PSUtil does not work the same on windows."
+)
+def test_proxy_cancelled_grpc_request_stream():
+    """
+    Test that DataServicerProxy and LogstreamServicerProxy should gracefully
+    close grpc stream when the request stream is cancelled.
+    """
+
+    proxier.CHECK_PROCESS_INTERVAL_S = 1
+    # The timeout has likely been set to 1 in an earlier test. Increase timeout
+    # to wait for the channel to become ready.
+    proxier.CHECK_CHANNEL_TIMEOUT_S = 5
+    os.environ["TIMEOUT_FOR_SPECIFIC_SERVER_S"] = "5"
+    pm, free_ports = start_ray_and_proxy_manager(n_ports=2)
+
+    data_servicer = proxier.DataServicerProxy(pm)
+    logstream_servicer = proxier.LogstreamServicerProxy(pm)
+
+    # simulate cancelled grpc request stream
+    # https://github.com/grpc/grpc/blob/v1.43.0/src/python/grpcio/grpc/_server.py#L353-L354
+    class Cancelled:
+        def __iter__(self):
+            return self
+
+        def __next__(self):
+            raise grpc.RpcError()
+
+    context = MagicMock()
+    context.set_code = MagicMock()
+    context.set_details = MagicMock()
+    context.invocation_metadata = MagicMock(
+        return_value=[
+            ("client_id", "client1"),
+            ("reconnecting", "False"),
+        ]
+    )
+
+    init = ray_client_pb2.DataRequest(
+        req_id=1,
+        init=ray_client_pb2.InitRequest(job_config=pickle.dumps(JobConfig())),
+    )
+
+    for _ in data_servicer.Datapath(chain([init], Cancelled()), context):
+        pass
+    for _ in logstream_servicer.Logstream(Cancelled(), context):
+        pass
+
+    assert not context.set_code.called, "grpc error should not be set"
+    assert not context.set_details.called, "grpc error should not be set"
+
+    class Rendezvous:
+        def __iter__(self):
+            return self
+
+        def __next__(self):
+            raise grpc._Rendezvous()
+
+    context.invocation_metadata = MagicMock(
+        return_value=[
+            ("client_id", "client2"),
+            ("reconnecting", "False"),
+        ]
+    )
+
+    for _ in data_servicer.Datapath(chain([init], Rendezvous()), context):
+        pass
+    for _ in logstream_servicer.Logstream(Rendezvous(), context):
+        pass
+
+    assert context.set_code.called, "grpc error should be set"
+    assert context.set_details.called, "grpc error should be set"
+
+
 if __name__ == "__main__":
     import sys
 

python/ray/util/client/server/proxier.py

@@ -608,6 +608,30 @@ def prepare_runtime_init_req(
     return (init_request, new_job_config)
 
 
+class RequestIteratorProxy:
+    def __init__(self, request_iterator):
+        self.request_iterator = request_iterator
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        try:
+            return next(self.request_iterator)
+        except grpc.RpcError as e:
+            # To stop proxying already CANCLLED request stream gracefully,
+            # we only translate the exact grpc.RpcError to StopIteration,
+            # not its subsclasses. ex: grpc._Rendezvous
+            # https://github.com/grpc/grpc/blob/v1.43.0/src/python/grpcio/grpc/_server.py#L353-L354
+            # This fixes the https://github.com/ray-project/ray/issues/23865
+            if type(e) != grpc.RpcError:
+                raise e  # re-raise other grpc exceptions
+            logger.exception(
+                "Stop iterating cancelled request stream with the following exception:"
+            )
+            raise StopIteration
+
+
 class DataServicerProxy(ray_client_pb2_grpc.RayletDataStreamerServicer):
     def __init__(self, proxy_manager: ProxyManager):
         self.num_clients = 0
@@ -635,6 +659,7 @@ def modify_connection_info_resp(
         return modified_resp
 
     def Datapath(self, request_iterator, context):
+        request_iterator = RequestIteratorProxy(request_iterator)
         cleanup_requested = False
         start_time = time.time()
         client_id = _get_client_id_from_context(context)
@@ -761,6 +786,7 @@ def __init__(self, proxy_manager: ProxyManager):
         self.proxy_manager = proxy_manager
 
     def Logstream(self, request_iterator, context):
+        request_iterator = RequestIteratorProxy(request_iterator)
         client_id = _get_client_id_from_context(context)
         if client_id == "":
             return