etcdserver: add more detailed traces on linearized reading #12335
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tangcong
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Sep 25, 2020
| @@ -775,6 +778,7 @@ func (s *EtcdServer) linearizableReadLoop() { | |||
| if !done { | |||
| continue | |||
| } | |||
| trace.Step("read index received") | |||
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can we add following fields to improve observability?
trace.AddField(traceutil.Field{Key: "appliedIndex", Value: s.getAppliedIndex})
trace.AddField(traceutil.Field{Key: "readStateIndex", Value: rs.Index})
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ci is failed. https://travis-ci.com/github/etcd-io/etcd/jobs/391026189
PierreZ
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tangcong
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Sep 25, 2020
etcdserver/v3_server.go
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| @@ -715,6 +716,9 @@ func (s *EtcdServer) linearizableReadLoop() { | |||
| return | |||
| } | |||
|
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| // as a single loop is can unlock multiple reads, it is not very useful | |||
| // to propagate the trace from Txn or Range. | |||
| trace := traceutil.New("linearizableReadLoop", s.lg) | |||
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lg should be s.getLogger().
To improve debuggability of `agreement among raft nodes before linearized reading`, we added some tracing inside `linearizableReadLoop`. This will allow us to know the timing of `s.r.ReadIndex` vs `s.applyWait.Wait(rs.Index)`.
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lgtm. thanks @PierreZ |
This was referenced Jul 19, 2022
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This PR is related to #11884
Why
To improve debuggability of
agreement among raft nodes before linearized reading, we added some tracing insidelinearizableReadLoop.This will allow us to know the timing of
s.r.ReadIndexvss.applyWait.Wait(rs.Index).Results
The patch has been deployed on clusters running v3.4.9, here's some traces:
{ "level": "info", "ts": "2020-09-22T12:54:01.021Z", "caller": "traceutil/trace.go:152", "msg": "trace[2138445431] linearizableReadLoop", "detail": "", "duration": "855.447896ms", "start": "2020-09-22T12:54:00.166Z", "end": "2020-09-22T12:54:01.021Z", "steps": [ "trace[2138445431] read index received (duration: 824.408µs)", "trace[2138445431] applied index is now lower than readState.Index (duration: 854.622058ms)" ] }