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client: fix race between transport draining and new RPCs (#2919)
Before these fixes, it was possible to see errors on new RPCs after a connection began draining, and before establishing a new connection. There is an inherent race between choosing a SubConn and attempting to creating a stream on it. We should be able to avoid application-visible RPC errors due to this with transparent retry. However, several bugs were preventing this from working correctly: 1. Non-wait-for-ready RPCs were skipping transparent retry, though the retry design calls for retrying them. 2. The transport closed itself (and would consequently error new RPCs) before notifying the SubConn that it was draining. 3. The SubConn wasn't synchronously updating itself once it was notified about the closing or draining state. 4. The SubConn would go into the TRANSIENT_FAILURE state instantaneously, causing RPCs to fail instead of queue.
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/* | ||
* | ||
* Copyright 2019 gRPC authors. | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
* | ||
*/ | ||
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package test | ||
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import ( | ||
"context" | ||
"net" | ||
"testing" | ||
"time" | ||
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"google.golang.org/grpc" | ||
"google.golang.org/grpc/keepalive" | ||
testpb "google.golang.org/grpc/test/grpc_testing" | ||
) | ||
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// TestGracefulClientOnGoAway attempts to ensure that when the server sends a | ||
// GOAWAY (in this test, by configuring max connection age on the server), a | ||
// client will never see an error. This requires that the client is appraised | ||
// of the GOAWAY and updates its state accordingly before the transport stops | ||
// accepting new streams. If a subconn is chosen by a picker and receives the | ||
// goaway before creating the stream, an error will occur, but upon transparent | ||
// retry, the clientconn will ensure a ready subconn is chosen. | ||
func (s) TestGracefulClientOnGoAway(t *testing.T) { | ||
const maxConnAge = 100 * time.Millisecond | ||
const testTime = maxConnAge * 10 | ||
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ss := &stubServer{ | ||
emptyCall: func(context.Context, *testpb.Empty) (*testpb.Empty, error) { | ||
return &testpb.Empty{}, nil | ||
}, | ||
} | ||
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s := grpc.NewServer(grpc.KeepaliveParams(keepalive.ServerParameters{MaxConnectionAge: maxConnAge})) | ||
defer s.Stop() | ||
testpb.RegisterTestServiceServer(s, ss) | ||
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lis, err := net.Listen("tcp", "localhost:0") | ||
if err != nil { | ||
t.Fatalf("Failed to create listener: %v", err) | ||
} | ||
go s.Serve(lis) | ||
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cc, err := grpc.Dial(lis.Addr().String(), grpc.WithInsecure()) | ||
if err != nil { | ||
t.Fatalf("Failed to dial server: %v", err) | ||
} | ||
defer cc.Close() | ||
c := testpb.NewTestServiceClient(cc) | ||
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endTime := time.Now().Add(testTime) | ||
for time.Now().Before(endTime) { | ||
ctx, cancel := context.WithTimeout(context.Background(), time.Second) | ||
if _, err := c.EmptyCall(ctx, &testpb.Empty{}); err != nil { | ||
t.Fatalf("EmptyCall(_, _) = _, %v; want _, <nil>", err) | ||
} | ||
cancel() | ||
} | ||
} |