Hey Guozhang, Usually I think such naming inconsistencies are best avoided. It adds another level of confusion for people who have to dip into the code, figure out a problem, and ultimately explain it. Since we already have the PreparingRebalance state, maybe we could just rename the AwaitingSync state to CompletingRebalance?
-Jason On Thu, Aug 3, 2017 at 6:09 PM, Guozhang Wang <wangg...@gmail.com> wrote: > From an ops person's view who are mostly likely watching the metrics these > names may not be very clear as people may not know the internals well. I'd > prefer PrepareRebalance and CompleteRebalance since they may be easier to > understand thought not 100 percent accurately match to internal > implementation. > > > Guozhang > > > On Thu, Aug 3, 2017 at 4:14 PM, Jason Gustafson <ja...@confluent.io> > wrote: > > > Hey Colin, Guozhang, > > > > I agree the current state names are not ideal for end users. I tend to > see > > the rebalance as joining the group and receiving the assignment. Maybe > the > > states could be named in those terms? For example: RebalanceJoin and > > RebalanceAssignment. What do you think? > > > > -Jason > > > > On Fri, Jul 28, 2017 at 11:18 AM, Guozhang Wang <wangg...@gmail.com> > > wrote: > > > > > I feel we can change `AwaitSync` to `completeRebalance` while keeping > the > > > other as is. > > > > > > cc Jason? > > > > > > Guozhang > > > > > > On Fri, Jul 28, 2017 at 10:08 AM, Colin McCabe <cmcc...@apache.org> > > wrote: > > > > > >> Thanks for the explanation. I guess maybe we should just keep the > group > > >> names as they are, then? > > >> > > >> best, > > >> Colin > > >> > > >> > > >> On Wed, Jul 26, 2017, at 11:25, Guozhang Wang wrote: > > >> > To me `PreparingRebalance` sounds better than `StartingRebalance` > > since > > >> > only by the end of that stage we have formed a new group. More > > >> > specifically, this this the workflow from the coordinator's point of > > >> > view: > > >> > > > >> > 1. decided to trigger a rebalance, enter PreparingRebalance phase; > > >> > | > > >> > | send out error code for all heartbeat reponses > > >> > \|/ > > >> > | > > >> > | waiting for join group requests from members > > >> > \|/ > > >> > 2. formed a new group, increment the generation number, now start > > >> > rebalancing, entering AwaitSync phase: > > >> > | > > >> > | send out the join group responses for whoever > > >> > requested join > > >> > \|/ > > >> > | > > >> > | waiting for the sync group request from the > > leader > > >> > \|/ > > >> > 3. received assignment from the leader; the rebalance has ended, > start > > >> > ticking for all members, entering Stable phase. > > >> > | > > >> > | for whoever else sending the sync group > request, > > >> > reply with the assignment > > >> > \|/ > > >> > > > >> > So from the coordinator's point of view the rebalance starts at > > >> beginning > > >> > of step 2 and ends at beginning of step 3. Maybe we can rename > > >> > `AwaitSync` > > >> > itself to `CompletingRebalance`. > > >> > > > >> > Guozhang > > >> > > > >> > > > >> > > > >> > On Tue, Jul 25, 2017 at 6:44 AM, Ismael Juma <ism...@juma.me.uk> > > wrote: > > >> > > > >> > > Hi Guozhang, > > >> > > > > >> > > Thanks for the clarification. The naming does seem a bit unclear. > > >> Maybe > > >> > > `PreparingRebalance` could be `StartingRebalance` or something > that > > >> makes > > >> > > it clear that it is part of the rebalance instead of a step before > > the > > >> > > actual rebalance. `AwaitingSync` could also be > > `CompletingRebalance`, > > >> but > > >> > > not sure if that's better. > > >> > > > > >> > > Ismael > > >> > > > > >> > > On Mon, Jul 24, 2017 at 7:02 PM, Guozhang Wang < > wangg...@gmail.com> > > >> wrote: > > >> > > > > >> > > > Actually Rebalancing includes two steps, and we name them > > >> > > PrepareRebalance > > >> > > > and WaitSync (arguably they may not be the best names). But > these > > >> two > > >> > > steps > > >> > > > together should be treated as the complete rebalance cycle. > > >> > > > > > >> > > > > > >> > > > Guozhang > > >> > > > > > >> > > > On Mon, Jul 24, 2017 at 10:46 AM, Colin McCabe < > > cmcc...@apache.org> > > >> > > wrote: > > >> > > > > > >> > > > > Hi all, > > >> > > > > > > >> > > > > I think maybe it makes sense to rename the > "PreparingRebalance" > > >> > > consumer > > >> > > > > group state to "Rebalancing." To me, "Preparing" implies that > > >> there > > >> > > > > will be a later "rebalance" state that follows-- but there is > > not. > > >> > > > > Since we're now exposing this state name publicly in these > > >> metrics, > > >> > > > > perhaps it makes sense to do this rename now. Thoughts? > > >> > > > > > > >> > > > > best, > > >> > > > > Colin > > >> > > > > > > >> > > > > > > >> > > > > On Fri, Jul 21, 2017, at 13:52, Colin McCabe wrote: > > >> > > > > > That's a good point. I revised the KIP to add metrics for > all > > >> the > > >> > > > group > > >> > > > > > states. > > >> > > > > > > > >> > > > > > best, > > >> > > > > > Colin > > >> > > > > > > > >> > > > > > > > >> > > > > > On Fri, Jul 21, 2017, at 12:08, Guozhang Wang wrote: > > >> > > > > > > Ah, that's right Jason. > > >> > > > > > > > > >> > > > > > > With that I can be convinced to add one metric per each > > state. > > >> > > > > > > > > >> > > > > > > Guozhang > > >> > > > > > > > > >> > > > > > > On Fri, Jul 21, 2017 at 11:44 AM, Jason Gustafson < > > >> > > > ja...@confluent.io> > > >> > > > > > > wrote: > > >> > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > "Dead" and "Empty" states are transient: groups > usually > > >> only > > >> > > > > leaves in > > >> > > > > > > > this > > >> > > > > > > > > state for a short while and then being deleted or > > >> transited to > > >> > > > > other > > >> > > > > > > > > states. > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > This is not strictly true for the "Empty" state which we > > >> also use > > >> > > > to > > >> > > > > > > > represent simple groups which only use the coordinator > to > > >> store > > >> > > > > offsets. I > > >> > > > > > > > think we may as well cover all the states if we're going > > to > > >> cover > > >> > > > > any of > > >> > > > > > > > them specifically. > > >> > > > > > > > > > >> > > > > > > > -Jason > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > On Fri, Jul 21, 2017 at 9:45 AM, Guozhang Wang < > > >> > > wangg...@gmail.com > > >> > > > > > > >> > > > > wrote: > > >> > > > > > > > > > >> > > > > > > > > My two cents: > > >> > > > > > > > > > > >> > > > > > > > > "Dead" and "Empty" states are transient: groups > usually > > >> only > > >> > > > > leaves in > > >> > > > > > > > this > > >> > > > > > > > > state for a short while and then being deleted or > > >> transited to > > >> > > > > other > > >> > > > > > > > > states. > > >> > > > > > > > > > > >> > > > > > > > > Since we have the existing "*NumGroups*" metric, > > >> `*NumGroups - > > >> > > > > > > > > **NumGroupsRebalancing > > >> > > > > > > > > - **NumGroupsAwaitingSync`* should cover the above > > three, > > >> where > > >> > > > > "Stable" > > >> > > > > > > > > should be contributing most of the counts: If we have > a > > >> bug > > >> > > that > > >> > > > > causes > > >> > > > > > > > the > > >> > > > > > > > > num.Dead / Empty to keep increasing, then we would > > observe > > >> > > > > `NumGroups` > > >> > > > > > > > keep > > >> > > > > > > > > increasing which should be sufficient for alerting. > And > > >> trouble > > >> > > > > shooting > > >> > > > > > > > of > > >> > > > > > > > > the issue could be relying on the log4j. > > >> > > > > > > > > > > >> > > > > > > > > *Guozhang* > > >> > > > > > > > > > > >> > > > > > > > > On Fri, Jul 21, 2017 at 7:19 AM, Ismael Juma < > > >> > > ism...@juma.me.uk> > > >> > > > > wrote: > > >> > > > > > > > > > > >> > > > > > > > > > Thanks for the KIP, Colin. This will definitely be > > >> useful. > > >> > > One > > >> > > > > > > > question: > > >> > > > > > > > > > would it be useful to have a metric for for the > number > > >> of > > >> > > > groups > > >> > > > > in > > >> > > > > > > > each > > >> > > > > > > > > > possible state? The KIP suggests > "PreparingRebalance" > > >> and > > >> > > > > > > > "AwaitingSync". > > >> > > > > > > > > > That leaves "Stable", "Dead" and "Empty". Are those > > not > > >> > > useful? > > >> > > > > > > > > > > > >> > > > > > > > > > Ismael > > >> > > > > > > > > > > > >> > > > > > > > > > On Thu, Jul 20, 2017 at 6:52 PM, Colin McCabe < > > >> > > > > cmcc...@apache.org> > > >> > > > > > > > > wrote: > > >> > > > > > > > > > > > >> > > > > > > > > > > Hi all, > > >> > > > > > > > > > > > > >> > > > > > > > > > > I posted "KIP-180: Add a broker metric specifying > > the > > >> > > number > > >> > > > of > > >> > > > > > > > > consumer > > >> > > > > > > > > > > group rebalances in progress" for discussion: > > >> > > > > > > > > > > > > >> > > > > > > > > > > https://cwiki.apache.org/confl > > >> uence/display/KAFKA/KIP- > > >> > > > > > > > > > > 180%3A+Add+a+broker+metric+ > > specifying+the+number+of+ > > >> > > > > > > > > > > consumer+group+rebalances+in+progress > > >> > > > > > > > > > > > > >> > > > > > > > > > > Check it out. > > >> > > > > > > > > > > > > >> > > > > > > > > > > cheers, > > >> > > > > > > > > > > Colin > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > -- > > >> > > > > > > > > -- Guozhang > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > -- > > >> > > > > > > -- Guozhang > > >> > > > > > > >> > > > > > >> > > > > > >> > > > > > >> > > > -- > > >> > > > -- Guozhang > > >> > > > > > >> > > > > >> > > > >> > > > >> > > > >> > -- > > >> > -- Guozhang > > >> > > > > > > > > > > > > -- > > > -- Guozhang > > > > > > > > > -- > -- Guozhang >
