client: fix race between transport draining and new RPCs #2919
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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.
menghanl
approved these changes
Jul 22, 2019
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@dfawley Can we confirm 1.23 release date? https://github.com/grpc/grpc-go/milestone/21 says August 13. etcd is using 1.22. Would like to use 1.23 with this fix for our 3.4 release. Thanks! /cc @jpbetz |
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@gyuho The milestone has the right date. Release 1.23 is scheduled for August 13. |
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@menghanl Thanks for the confirmation! |
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Fixes #2767
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:
Non-wait-for-ready RPCs were skipping transparent retry, though the retry
design calls for retrying them.
The transport closed itself (and would consequently error new RPCs) before
notifying the SubConn that it was draining.
The SubConn wasn't synchronously updating itself once it was notified about
the closing or draining state.
The SubConn would go into the TRANSIENT_FAILURE state instantaneously,
causing RPCs to fail instead of queue.