etcdserver: remove possibly compacted entry look-up #7513
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heyitsanthony
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Mar 15, 2017
etcdserver/server.go
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| @@ -1254,8 +1257,9 @@ func (s *EtcdServer) sendMergedSnap(merged snap.Message) { | |||
| // apply takes entries received from Raft (after it has been committed) and | |||
| // applies them to the current state of the EtcdServer. | |||
| // The given entries should not be empty. | |||
| func (s *EtcdServer) apply(es []raftpb.Entry, confState *raftpb.ConfState) (uint64, bool) { | |||
| var applied uint64 | |||
| func (s *EtcdServer) apply(es []raftpb.Entry, confState *raftpb.ConfState) (uint64, uint64, bool) { | |||
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func (s *EtcdServer) apply(es []raftpb.Entry, confState *raftpb.ConfState) (appliedt uint64, appliedi uint64, shouldStop bool) { to make the return values clearer?
|
lgtm defer to @xiang90 |
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xiang90
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Mar 15, 2017
etcdserver/server.go
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| } | ||
| return applied, shouldstop | ||
| return |
|
LGTM. Great analysis. |
Fix etcd-io#7470. This patch removes unnecessary term look-up in 'createMergedSnapshotMessage', which can trigger panic if raft entry at etcdProgress.appliedi got compacted by subsequent 'MsgSnap' messages--if a follower is being (in this case, network latency spikes), it could receive subsequent 'MsgSnap' requests from leader. etcd server-side 'applyAll' routine and raft's Ready processing routine becomes asynchronous after raft entries are persisted. And given that raft Ready routine takes less time to finish, it is possible that second 'MsgSnap' is being handled, while the slow 'applyAll' is still processing the first(old) 'MsgSnap'. Then raft Ready routine can compact the log entries at future index to 'applyAll'. That is how 'createMergedSnapshotMessage' tried to look up raft term with outdated etcdProgress.appliedi. Signed-off-by: Gyu-Ho Lee <[email protected]>
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Codecov Report
@@ Coverage Diff @@
## master #7513 +/- ##
=========================================
Coverage ? 70.25%
=========================================
Files ? 320
Lines ? 26203
Branches ? 0
=========================================
Hits ? 18408
Misses ? 6338
Partials ? 1457
Continue to review full report at Codecov.
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Fix #7470.
This patch removes unnecessary term look-up in
'createMergedSnapshotMessage', which can trigger panic
if raft entry at etcdProgress.appliedi got compacted
by subsequent 'MsgSnap' messages--if a follower is
being (in this case, network latency spikes) slow, it
could receive subsequent 'MsgSnap' requests from leader.
etcd server-side 'applyAll' routine and raft's Ready
processing routine becomes asynchronous after raft
entries are persisted. And given that raft Ready routine
takes less time to finish, it is possible that second
'MsgSnap' is being handled, while the slow 'applyAll'
is still processing the first(old) 'MsgSnap'. Then raft
Ready routine can compact the log entries at future
index to 'applyAll'. That is how 'createMergedSnapshotMessage'
tried to look up raft term with outdated etcdProgress.appliedi.