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KAFKA-9232: Coordinator new member heartbeat completion does not work for JoinGroup v3 #7753

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Merged
hachikuji merged 8 commits into from
Dec 23, 2019
Merged

KAFKA-9232: Coordinator new member heartbeat completion does not work for JoinGroup v3 #7753

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61a2acf
return true when isNew
ableegoldman Nov 27, 2019
74a9fe9
reorder calls in onCompleteJoin
ableegoldman Nov 27, 2019
8392273
Revert "reorder calls in onCompleteJoin"
ableegoldman Dec 11, 2019
151477f
typo
ableegoldman Dec 11, 2019
321fb1c
should fall to new member timeout
ableegoldman Dec 18, 2019
18d441d
add unit test
ableegoldman Dec 20, 2019
d4d9209
indentation
ableegoldman Dec 20, 2019
69477f8
refactor test
ableegoldman Dec 20, 2019
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4 changes: 3 additions & 1 deletion core/src/main/scala/kafka/coordinator/group/MemberMetadata.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -88,7 +88,9 @@ private[group] class MemberMetadata(var memberId: String,
def shouldKeepAlive(deadlineMs: Long): Boolean = {
if (isAwaitingJoin)
!isNew || latestHeartbeat + GroupCoordinator.NewMemberJoinTimeoutMs > deadlineMs
else awaitingSyncCallback != null ||

@ableegoldman ableegoldman Nov 27, 2019

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replaced awaitingSyncCallback != null with isAwaitingSync

else if (isNew || isAwaitingSync)

@ableegoldman ableegoldman Nov 27, 2019

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In onCompleteJoin, we call

  1. group.maybeInvokeJoinCallback(member, joinResult)
  2. completeAndScheduleNextHeartbeatExpiration(group, member)
  3. member.isNew = false

In 1. we ultimately set member.isAwaitingJoin to false, so we never reach the first branch in this case.

I refactored this a bit to reflect what (I think) makes sense: we want to always return true in the special cases of a) awaiting Sync, and b) between awaiting the Join and awaiting the Sync, ie, when isNew = true -- otherwise, we fall back to the usual case, ie, just return whether we've seen a heartbeat within the deadline or not

@ableegoldman ableegoldman Nov 27, 2019

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Alternatively we could leave this method alone and change the ordering in onCompleteJoin to

member.isNew = false
completeAndScheduleNextHeartbeatExpiration(group, member)
group.maybeInvokeJoinCallback(member, joinResult)

I think this also makes sense, and might be a bit more clear, but I'd want to verify that it's ok to move the heartbeat completion to before the group.maybeInvokeJoinCallback

@hachikuji hachikuji Nov 27, 2019

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I'm for simplifying if possible. What I am thinking is the following:

if (isNew)
  // New members are expired after the static join timeout
  latestHeartbeat + GroupCoordinator.NewMemberJoinTimeoutMs > deadlineMs
else if (isAwaitingJoin || isAwaitingSync)
  // Don't remove members as long as they have a request in purgatory
  true
else
  // Otherwise check for session expiration
  latestHeartbeat + sessionTimeoutMs > deadlineMs

Then I think this works with the reordering you suggested above:

member.isNew = false
completeAndScheduleNextHeartbeatExpiration(group, member)
group.maybeInvokeJoinCallback(member, joinResult)

Upon rebalance completion, the first check will fail since we set isNew to false and the second check will succeed because we haven't cleared the join callback yet. What do you think?

@ableegoldman ableegoldman Nov 27, 2019

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Ok yeah I like that, the shouldKeepAlive logic is much easier to follow

true
else
latestHeartbeat + sessionTimeoutMs > deadlineMs
}

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