I agree that we should make them consistent. I think RebalanceJoin and RebalanceAssignment are reasonable names. I think they are a bit more descriptive than `PreparingRebalance` and `CompletingRebalance`. If we need to add more states, it seems a little easier to do if the states are a bit more descriptive. I am OK with either of the 2 options as I think they are both better than the status quo.
Ismael On Fri, Aug 4, 2017 at 4:52 PM, Jason Gustafson <ja...@confluent.io> wrote: > 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 > > >
