I think I'm OK to always enable checkpointing, but I'm not sure if we want to checkpoint on every commit. Since in the extreme case users can commit on completed processing each record. So I think it is still valuable to have a checkpoint internal config in this KIP, which can be ignored if EOS is turned on. That being said, if most people are favoring checkpointing on each commit we can try that with this as well, since it won't change any public APIs and we can still add this config in the future if we do observe some users reporting it has huge perf impacts.
Guozhang On Fri, Feb 10, 2017 at 12:20 PM, Damian Guy <damian....@gmail.com> wrote: > I'm fine with that. Gouzhang? > On Fri, 10 Feb 2017 at 19:45, Matthias J. Sax <matth...@confluent.io> > wrote: > > > I am actually supporting Eno's view: checkpoint on every commit. > > > > @Dhwani: I understand your view and did raise the same question about > > performance trade-off with checkpoiting enabled/disabled etc. However, > > it seems that writing the checkpoint file is super cheap -- thus, there > > is nothing to gain performance wise by disabling it. > > > > For Streams EoS we do not need the checkpoint file -- but we should have > > a switch for EoS anyway and can disable the checkpoint file for this > > case. And even if there is no switch and we enable EoS all the time, we > > can get rid of the checkpoint file overall (making the parameter > obsolete). > > > > IMHO, if the config parameter is not really useful, we should not have > it. > > > > > > -Matthias > > > > > > On 2/10/17 9:27 AM, Damian Guy wrote: > > > Gouzhang, Thanks for the clarification. Understood. > > > > > > Eno, you are correct if we just used commit interval then we wouldn't > > need > > > a KIP. But, then we'd have no way of turning it off. > > > > > > On Fri, 10 Feb 2017 at 17:14 Eno Thereska <eno.there...@gmail.com> > > wrote: > > > > > >> A quick check: the checkpoint file is not new, we're just exposing a > > knob > > >> on when to set it, right? Would turning if off still do what it does > > today > > >> (i.e., write the checkpoint at the end when the user quits?) So it's > > not a > > >> new feature as such, I was only recommending we dial up the frequency > by > > >> default. With that option arguably we don't even need a KIP. > > >> > > >> Eno > > >> > > >> > > >> > > >>> On 10 Feb 2017, at 17:02, Guozhang Wang <wangg...@gmail.com> wrote: > > >>> > > >>> Damian, > > >>> > > >>> I was thinking if it is a new failure scenarios but as Eno pointed > out > > it > > >>> was not. > > >>> > > >>> Another thing I was considering is if it has any impact for > > incorporating > > >>> KIP-98 to avoid duplicates: if there is a failure in the middle of a > > >>> transaction, then upon recovery we cannot rely on the local state > store > > >>> file even if the checkpoint file exists, since the local state store > > file > > >>> may not be at the transaction boundaries. But since Streams will > likely > > >> to > > >>> have EOS as an opt-in I think it is still worthwhile to add this > > feature, > > >>> just keeping in mind that when EOS is turned on it may cease to be > > >>> effective. > > >>> > > >>> And yes, I'd suggest we leave the config value to be possibly > > >> non-positive > > >>> to indicate not turning on this feature for the reason above: if it > > will > > >>> not be effective then we want to leave it as an option to be turned > > off. > > >>> > > >>> Guozhang > > >>> > > >>> > > >>> On Fri, Feb 10, 2017 at 8:06 AM, Eno Thereska < > eno.there...@gmail.com> > > >>> wrote: > > >>> > > >>>> The overhead of writing to the checkpoint file should be much, much > > >>>> smaller than the overall overhead of doing a commit, so I think > tuning > > >> the > > >>>> commit time is sufficient to guide performance tradeoffs. > > >>>> > > >>>> Eno > > >>>> > > >>>>> On 10 Feb 2017, at 13:08, Dhwani Katagade < > > >> dhwani_katag...@persistent.co > > >>>> .in> wrote: > > >>>>> > > >>>>> May be for fine tuning the performance. > > >>>>> Say we don't need the checkpointing and would like to gain the lil > > bit > > >>>> of performance improvement by turning it off. > > >>>>> The trade off is between giving people control knobs vs > complicating > > >> the > > >>>> complete set of knobs. > > >>>>> > > >>>>> -dk > > >>>>> > > >>>>> On Friday 10 February 2017 04:05 PM, Eno Thereska wrote: > > >>>>>> I can't see why users would care to turn it off. > > >>>>>> > > >>>>>> Eno > > >>>>>>> On 10 Feb 2017, at 10:29, Damian Guy <damian....@gmail.com> > wrote: > > >>>>>>> > > >>>>>>> Hi Eno, > > >>>>>>> > > >>>>>>> Sounds good to me. The only reason i can think of is if we want > to > > be > > >>>> able > > >>>>>>> to turn it off. > > >>>>>>> Gouzhang - thoughts? > > >>>>>>> > > >>>>>>> On Fri, 10 Feb 2017 at 10:28 Eno Thereska < > eno.there...@gmail.com> > > >>>> wrote: > > >>>>>>> > > >>>>>>>> Question: if checkpointing is so cheap why not do it every > commit > > >>>>>>>> interval? That way we can get rid of this extra config variable > > and > > >>>> just > > >>>>>>>> use the existing commit interval. > > >>>>>>>> > > >>>>>>>> Less tuning knobs. > > >>>>>>>> > > >>>>>>>> Eno > > >>>>>>>> > > >>>>>>>>> On 10 Feb 2017, at 09:27, Damian Guy <damian....@gmail.com> > > wrote: > > >>>>>>>>> > > >>>>>>>>> Gouzhang, > > >>>>>>>>> > > >>>>>>>>> You've confused me. The failure scenarios you have described > are > > >> the > > >>>> same > > >>>>>>>>> as they are today. With the checkpoint files in place less data > > >> will > > >>>> be > > >>>>>>>>> replayed, so there will be fewer duplicates. > > >>>>>>>>> > > >>>>>>>>> Are you saying you'd like the option to turn checkpointing off? > > >>>>>>>>> > > >>>>>>>>> Thanks, > > >>>>>>>>> Damian > > >>>>>>>>> > > >>>>>>>>> On Thu, 9 Feb 2017 at 21:55 Guozhang Wang <wangg...@gmail.com> > > >>>> wrote: > > >>>>>>>>> > > >>>>>>>>>> Eno, > > >>>>>>>>>> > > >>>>>>>>>> You are right, it is not a new scenario. > > >>>>>>>>>> > > >>>>>>>>>> Thinking a bit more on how we could incorporate KIP-98 in > > >> Streams, I > > >>>>>>>> feel > > >>>>>>>>>> that if EOS is turned on inside Streams, then we probably > cannot > > >>>> always > > >>>>>>>>>> resume from the checkpointed offsets as it is not guaranteed > to > > be > > >>>>>>>>>> "consistent"; but since EOS may not be turned on by default > this > > >> is > > >>>>>>>> still > > >>>>>>>>>> worthwhile to add this feature I guess. > > >>>>>>>>>> > > >>>>>>>>>> About the default config values: I think the default value of > 5 > > >> min > > >>>> is > > >>>>>>>> OK > > >>>>>>>>>> to me, since restoration is usually faster than normal > > processing > > >>>>>>>> (unless > > >>>>>>>>>> your traffic was really high), about allowing it to be "turned > > >> off" > > >>>>>>>> with a > > >>>>>>>>>> non-positive value: I feel there are still values to keep this > > >> door > > >>>>>>>> open as > > >>>>>>>>>> in the future if EOS is turned on, people may just want to > turn > > >> off > > >>>>>>>>>> checkpointing anyways, or there maybe other scenarios that we > > have > > >>>> not > > >>>>>>>>>> realized yet. On the other hand, I would argue that it is less > > >>>> likely > > >>>>>>>> users > > >>>>>>>>>> mistakenly set it to a non-positive value. > > >>>>>>>>>> > > >>>>>>>>>> Guozhang > > >>>>>>>>>> > > >>>>>>>>>> On Thu, Feb 9, 2017 at 1:03 PM, Eno Thereska < > > >>>> eno.there...@gmail.com> > > >>>>>>>>>> wrote: > > >>>>>>>>>> > > >>>>>>>>>>> Hi Guozhang, > > >>>>>>>>>>> > > >>>>>>>>>>> It seems to me we have the same semantics today. Are you > saying > > >>>> there > > >>>>>>>> is > > >>>>>>>>>> a > > >>>>>>>>>>> new failure scenario? > > >>>>>>>>>>> > > >>>>>>>>>>> Thanks, > > >>>>>>>>>>> Eno > > >>>>>>>>>>> > > >>>>>>>>>>>> On 9 Feb 2017, at 19:42, Guozhang Wang <wangg...@gmail.com> > > >>>> wrote: > > >>>>>>>>>>>> > > >>>>>>>>>>>> More specifically, here is my reasoning of failure cases, > and > > >>>> would > > >>>>>>>>>> like > > >>>>>>>>>>> to > > >>>>>>>>>>>> get your feedbacks: > > >>>>>>>>>>>> > > >>>>>>>>>>>> *StreamTask* > > >>>>>>>>>>>> > > >>>>>>>>>>>> For stream-task, the committing order is 1) flush state (may > > >> send > > >>>> more > > >>>>>>>>>>>> records to changelog in producer), 2) flush producer, 3) > > commit > > >>>>>>>>>> upstream > > >>>>>>>>>>>> offsets. My understanding is that the writing of the > > checkpoint > > >>>> file > > >>>>>>>>>> will > > >>>>>>>>>>>> between 2) and 3). So thatt he new order will be 1) flush > > state, > > >>>> 2) > > >>>>>>>>>> flush > > >>>>>>>>>>>> producer, 3) write checkpoint file (when necessary), 4) > commit > > >>>>>>>> upstream > > >>>>>>>>>>>> offsets. > > >>>>>>>>>>>> > > >>>>>>>>>>>> And we have a bunch of "changelog offsets" regarding the > > state: > > >> a) > > >>>>>>>>>> offset > > >>>>>>>>>>>> corresponding to the image of the persistent file, name it > > point > > >>>> A, b) > > >>>>>>>>>>> log > > >>>>>>>>>>>> end offset, name it offset B, c) checkpoint file recorded > > >> offset, > > >>>> name > > >>>>>>>>>> it > > >>>>>>>>>>>> offset C, d) offset corresponding to the current committed > > >>>> upstream > > >>>>>>>>>>> offset, > > >>>>>>>>>>>> name it offset D. > > >>>>>>>>>>>> > > >>>>>>>>>>>> Now let's talk about the failure cases: > > >>>>>>>>>>>> > > >>>>>>>>>>>> If there is a crash between 1) and 2), then A > B = C = D. > In > > >> this > > >>>>>>>>>> case, > > >>>>>>>>>>> if > > >>>>>>>>>>>> we restore, we will replay no logs at all since B = C while > > the > > >>>>>>>>>>> persistent > > >>>>>>>>>>>> state file is actually "ahead of time", and we will start > > >>>> reprocessing > > >>>>>>>>>>>> since from the input offset corresponding to D = B < A and > > hence > > >>>> have > > >>>>>>>>>>> some > > >>>>>>>>>>>> duplicated, *which will be incorrect* if the update logic > > >> involve > > >>>>>>>>>> reading > > >>>>>>>>>>>> the state store values as well (i.e. not a blind write), > e.g. > > >>>>>>>>>>> aggregations. > > >>>>>>>>>>>> If there is a crash between 2) and 3), then A = B > C = D. > > When > > >> we > > >>>>>>>>>>> restore, > > >>>>>>>>>>>> we will replay from C -> B = A, and then start reprocessing > > from > > >>>> input > > >>>>>>>>>>>> offset corresponding to D < A, and same issue applies as > > above. > > >>>>>>>>>>>> > > >>>>>>>>>>>> If there is a crash between 3) and 4), then A = B = C > D. > > When > > >> we > > >>>>>>>>>>> restore, > > >>>>>>>>>>>> we will not replay, and then start reprocessing from input > > >> offset > > >>>>>>>>>>>> corresponding to D < A, and same issue applies as above. > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> *StandbyTask* > > >>>>>>>>>>>> > > >>>>>>>>>>>> We only do one operation today, which is 1) flush state, I > > think > > >>>> we > > >>>>>>>>>> will > > >>>>>>>>>>>> add the writing of the checkpoint file after it as step 2). > > >>>>>>>>>>>> > > >>>>>>>>>>>> Failure cases again: offset A -> correspond to the image of > > the > > >>>> file, > > >>>>>>>>>>>> offset B -> changelog end offset, offset C -> written as in > > the > > >>>>>>>>>>> checkpoint > > >>>>>>>>>>>> file. > > >>>>>>>>>>>> > > >>>>>>>>>>>> If there is a crash between 1) and 2), then B >= A > C (B > >= A > > >>>> because > > >>>>>>>>>> we > > >>>>>>>>>>>> are reading from changelog topic so A will never be greater > > than > > >>>> B), > > >>>>>>>>>>>> > > >>>>>>>>>>>> 1) and if this task resumes as a standby task, we will > resume > > >>>>>>>>>> restoration > > >>>>>>>>>>>> from offset C, and a few duplicates from C -> A will be > > applied > > >>>> again > > >>>>>>>>>> to > > >>>>>>>>>>>> local state files, then continue from A -> B, *this is OK* > > since > > >>>> they > > >>>>>>>>>> do > > >>>>>>>>>>>> not incur any computations hence no side effects and are all > > >>>>>>>>>> idempotent. > > >>>>>>>>>>>> 2) and if this task resumes as a stream task, we will replay > > >>>>>>>> changelogs > > >>>>>>>>>>>> from C -> A, with duplicated updates, and then from A -> B. > > This > > >>>> is > > >>>>>>>>>> also > > >>>>>>>>>>> OK > > >>>>>>>>>>>> for the same reason as above. > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> So it seems to me that this is not safe for a StreamTask, or > > >>>> maybe the > > >>>>>>>>>>>> writing of the checkpoint file in your mind is different? > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> Guozhang > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> On Thu, Feb 9, 2017 at 11:02 AM, Guozhang Wang < > > >>>> wangg...@gmail.com> > > >>>>>>>>>>> wrote: > > >>>>>>>>>>>>> A quick question re: `We will add the above config > parameter > > to > > >>>>>>>>>>>>> *StreamsConfig*. During *StreamTask#commit()*, > > >>>>>>>> *StandbyTask#commit()*, > > >>>>>>>>>>>>> and *GlobalUpdateStateTask#flushState()* we will check if > the > > >>>>>>>>>>> checkpoint > > >>>>>>>>>>>>> interval has elapsed and write the checkpoint file.` > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> Will the writing of the checkpoint file happen before the > > >>>> flushing of > > >>>>>>>>>>> the > > >>>>>>>>>>>>> state manager? > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> Guozhang > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> On Thu, Feb 9, 2017 at 10:48 AM, Matthias J. Sax < > > >>>>>>>>>> matth...@confluent.io > > >>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>> > > >>>>>>>>>>>>>> But 5 min means, that we (in the worst case) need to reply > > >> data > > >>>> from > > >>>>>>>>>>> the > > >>>>>>>>>>>>>> last 5 minutes to get the store ready. > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>>> So why not go with the min possible value of 30 seconds to > > >>>> speed up > > >>>>>>>>>>> this > > >>>>>>>>>>>>>> process if the impact is negligible anyway? > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>>> What do you gain by being conservative? > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>>> -Matthias > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>>> On 2/9/17 2:54 AM, Damian Guy wrote: > > >>>>>>>>>>>>>>> Why shouldn't it be 5 minutes? ;-) > > >>>>>>>>>>>>>>> It is a finger in the air number. Based on the testing i > > did > > >> it > > >>>>>>>>>> shows > > >>>>>>>>>>>>>> that > > >>>>>>>>>>>>>>> there isn't much, if any, overhead when checkpointing a > > >> single > > >>>>>>>> store > > >>>>>>>>>>> on > > >>>>>>>>>>>>>> the > > >>>>>>>>>>>>>>> commit interval. The default commit interval is 30 > seconds, > > >> so > > >>>> it > > >>>>>>>>>>> could > > >>>>>>>>>>>>>>> possibly be set to that. However, i'd prefer to be a > little > > >>>>>>>>>>>>>> conservative so > > >>>>>>>>>>>>>>> 5 minutes seemed reasonable. > > >>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>> On Thu, 9 Feb 2017 at 10:25 Michael Noll < > > >> mich...@confluent.io > > >>>>> > > >>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>> Damian, > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> could you elaborate briefly why the default value should > > be > > >> 5 > > >>>>>>>>>>> minutes? > > >>>>>>>>>>>>>>>> What are the considerations, assumptions, etc. that go > > into > > >>>>>>>> picking > > >>>>>>>>>>>>>> this > > >>>>>>>>>>>>>>>> value? > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> Right now, in the KIP and in this discussion, "5 mins" > > looks > > >>>> like > > >>>>>>>> a > > >>>>>>>>>>>>>> magic > > >>>>>>>>>>>>>>>> number to me. :-) > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> -Michael > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>> On Thu, Feb 9, 2017 at 11:03 AM, Damian Guy < > > >>>> damian....@gmail.com > > >>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>> I've ran the SimpleBenchmark with checkpoint on and off > > to > > >>>> see > > >>>>>>>>>> what > > >>>>>>>>>>>>>> the > > >>>>>>>>>>>>>>>>> impact is. It appears that there is very little impact, > > if > > >>>> any. > > >>>>>>>>>> The > > >>>>>>>>>>>>>>>> numbers > > >>>>>>>>>>>>>>>>> with checkpointing on actually look better, but that is > > >>>> likely > > >>>>>>>>>>> largely > > >>>>>>>>>>>>>>>> due > > >>>>>>>>>>>>>>>>> to external influences. > > >>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>> In any case, i'm going to suggest we go with a default > > >>>> checkpoint > > >>>>>>>>>>>>>>>> interval > > >>>>>>>>>>>>>>>>> of 5 minutes. I've update the KIP with this. > > >>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>> commit every 10 seconds (no checkpoint) > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/34798/287372.83751939767/29.570664980746017 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/35942/278226.0308274442/28.62945857214401 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/34677/288375.58035585546/29.673847218617528 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/34677/288375.58035585546/29.673847218617528 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/31192/320595.02436522185/32.98922800718133 > > >>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>> checkpoint every 10 seconds (same as commit interval) > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/36997/270292.185852907/27.81306592426413 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/32087/311652.69423754164/32.069062237043035 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/32895/303997.5680194558/31.281349749202004 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/33476/298721.4720994145/30.738439479029754 > > >>>>>>>>>>>>>>>>> Streams Performance [records/latency/rec-sec/MB-sec > > >>>>>>>> source+store]: > > >>>>>>>>>>>>>>>>> 10000000/33196/301241.1133871551/30.99771056753826 > > >>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>> On Wed, 8 Feb 2017 at 09:02 Damian Guy < > > >> damian....@gmail.com > > >>>>> > > >>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>> Matthias, > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> Fair point. I'll update it the KIP. > > >>>>>>>>>>>>>>>>>> Thanks > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> On Wed, 8 Feb 2017 at 05:49 Matthias J. Sax < > > >>>>>>>>>> matth...@confluent.io > > >>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>> Damian, > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> I am not strict about it either. However, if there is > no > > >>>>>>>>>> advantage > > >>>>>>>>>>> in > > >>>>>>>>>>>>>>>>>> disabling it, we might not want to allow it. This > would > > >>>> have the > > >>>>>>>>>>>>>>>>>> advantage to guard users to accidentally switch it > off. > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> -Matthias > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> On 2/3/17 2:03 AM, Damian Guy wrote: > > >>>>>>>>>>>>>>>>>>> Hi Matthias, > > >>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>> It possibly doesn't make sense to disable it, but > then > > >> i'm > > >>>> sure > > >>>>>>>>>>>>>>>> someone > > >>>>>>>>>>>>>>>>>>> will come up with a reason they don't want it! > > >>>>>>>>>>>>>>>>>>> I'm happy to change it such that the checkpoint > > interval > > >>>> must > > >>>>>>>>>> be > > > >>>>>>>>>>>>>> 0. > > >>>>>>>>>>>>>>>>>>> Cheers, > > >>>>>>>>>>>>>>>>>>> Damian > > >>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>> On Fri, 3 Feb 2017 at 01:29 Matthias J. Sax < > > >>>>>>>>>>> matth...@confluent.io> > > >>>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>>>> Thanks Damian. > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> One more question: "Checkpointing is disabled if the > > >>>>>>>> checkpoint > > >>>>>>>>>>>>>>>>> interval > > >>>>>>>>>>>>>>>>>>>> is set to a value <=0." > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> Does it make sense to disable check pointing? What's > > the > > >>>>>>>>>> tradeoff > > >>>>>>>>>>>>>>>>> here? > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> -Matthias > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> On 2/2/17 1:51 AM, Damian Guy wrote: > > >>>>>>>>>>>>>>>>>>>>> Hi Matthias, > > >>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> Thanks for the comments. > > >>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> 1. TBD - i need to do some performance tests and > try > > >> and > > >>>> work > > >>>>>>>>>>> out > > >>>>>>>>>>>>>> a > > >>>>>>>>>>>>>>>>>>>>> sensible default. > > >>>>>>>>>>>>>>>>>>>>> 2. Yes, you are correct. It could be a multiple of > > the > > >>>>>>>>>>>>>>>>>>>> commit.interval.ms. > > >>>>>>>>>>>>>>>>>>>>> But, that would also mean if you change the commit > > >>>> interval - > > >>>>>>>>>>> say > > >>>>>>>>>>>>>>>> you > > >>>>>>>>>>>>>>>>>>>> lower > > >>>>>>>>>>>>>>>>>>>>> it, then you might also need to change the > checkpoint > > >>>> setting > > >>>>>>>>>>>>>> (i.e, > > >>>>>>>>>>>>>>>>> you > > >>>>>>>>>>>>>>>>>>>>> still only want to checkpoint every n minutes). > > >>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>> On Wed, 1 Feb 2017 at 23:46 Matthias J. Sax < > > >>>>>>>>>>>>>> matth...@confluent.io > > >>>>>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>>>>>> Thanks for the KIP Damian. > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> I am wondering about two things: > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> 1. what should be the default value for the new > > >>>> parameter? > > >>>>>>>>>>>>>>>>>>>>>> 2. why is the new parameter provided in ms? > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> About (2): because > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> "the minimum checkpoint interval will be the value > > of > > >>>>>>>>>>>>>>>>>>>>>> commit.interval.ms. In effect the actual > checkpoint > > >>>>>>>> interval > > >>>>>>>>>>>>>> will > > >>>>>>>>>>>>>>>>> be > > >>>>>>>>>>>>>>>>>> a > > >>>>>>>>>>>>>>>>>>>>>> multiple of the commit interval" > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> it might be easier to just use an parameter that > is > > >>>>>>>>>>>>>>>>> "number-or-commit > > >>>>>>>>>>>>>>>>>>>>>> intervals". > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> -Matthias > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> On 2/1/17 7:29 AM, Damian Guy wrote: > > >>>>>>>>>>>>>>>>>>>>>>> Thanks for the comments Eno. > > >>>>>>>>>>>>>>>>>>>>>>> As for exactly once, i don't believe this matters > > as > > >>>> we are > > >>>>>>>>>>> just > > >>>>>>>>>>>>>>>>>>>>>> restoring > > >>>>>>>>>>>>>>>>>>>>>>> the change-log, i.e, the result of the > aggregations > > >>>> that > > >>>>>>>>>>>>>>>> previously > > >>>>>>>>>>>>>>>>>> ran > > >>>>>>>>>>>>>>>>>>>>>>> etc. So once initialized the state store will be > in > > >> the > > >>>>>>>> same > > >>>>>>>>>>>>>>>> state > > >>>>>>>>>>>>>>>>> as > > >>>>>>>>>>>>>>>>>>>> it > > >>>>>>>>>>>>>>>>>>>>>>> was before. > > >>>>>>>>>>>>>>>>>>>>>>> Having the checkpoint in a kafka topic is not > ideal > > >> as > > >>>> the > > >>>>>>>>>>> state > > >>>>>>>>>>>>>>>> is > > >>>>>>>>>>>>>>>>>> per > > >>>>>>>>>>>>>>>>>>>>>>> kafka streams instance. So each instance would > need > > >> to > > >>>>>>>> start > > >>>>>>>>>>>>>>>> with a > > >>>>>>>>>>>>>>>>>>>>>> unique > > >>>>>>>>>>>>>>>>>>>>>>> id that is persistent. > > >>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> Cheers, > > >>>>>>>>>>>>>>>>>>>>>>> Damian > > >>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>> On Wed, 1 Feb 2017 at 13:20 Eno Thereska < > > >>>>>>>>>>>>>> eno.there...@gmail.com > > >>>>>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>>>>>>>> As a follow up to my previous comment, have you > > >>>> thought > > >>>>>>>>>> about > > >>>>>>>>>>>>>>>>>> writing > > >>>>>>>>>>>>>>>>>>>>>> the > > >>>>>>>>>>>>>>>>>>>>>>>> checkpoint to a topic instead of a local file? > > That > > >>>> would > > >>>>>>>>>>> have > > >>>>>>>>>>>>>>>> the > > >>>>>>>>>>>>>>>>>>>>>>>> advantage that all metadata continues to be > > managed > > >> by > > >>>>>>>>>> Kafka, > > >>>>>>>>>>>>>> as > > >>>>>>>>>>>>>>>>>> well > > >>>>>>>>>>>>>>>>>>>> as > > >>>>>>>>>>>>>>>>>>>>>>>> fit with EoS. The potential disadvantage would > be > > a > > >>>> slower > > >>>>>>>>>>>>>>>>> latency, > > >>>>>>>>>>>>>>>>>>>>>> however > > >>>>>>>>>>>>>>>>>>>>>>>> if it is periodic as you mention, I'm not sure > > that > > >>>> would > > >>>>>>>>>> be > > >>>>>>>>>>> a > > >>>>>>>>>>>>>>>>> show > > >>>>>>>>>>>>>>>>>>>>>> stopper. > > >>>>>>>>>>>>>>>>>>>>>>>> Thanks > > >>>>>>>>>>>>>>>>>>>>>>>> Eno > > >>>>>>>>>>>>>>>>>>>>>>>>> On 1 Feb 2017, at 12:58, Eno Thereska < > > >>>>>>>>>>> eno.there...@gmail.com > > >>>>>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>>>>>>>>> Thanks Damian, this is a good idea and will > > reduce > > >>>> the > > >>>>>>>>>>> restore > > >>>>>>>>>>>>>>>>>> time. > > >>>>>>>>>>>>>>>>>>>>>>>> Looking forward, with exactly once and support > for > > >>>>>>>>>>> transactions > > >>>>>>>>>>>>>>>> in > > >>>>>>>>>>>>>>>>>>>>>> Kafka, I > > >>>>>>>>>>>>>>>>>>>>>>>> believe we'll have to add some support for > rolling > > >>>> back > > >>>>>>>>>>>>>>>>> checkpoints, > > >>>>>>>>>>>>>>>>>>>>>> e.g., > > >>>>>>>>>>>>>>>>>>>>>>>> when a transaction is aborted. We need to be > aware > > >> of > > >>>> that > > >>>>>>>>>>> and > > >>>>>>>>>>>>>>>>>> ideally > > >>>>>>>>>>>>>>>>>>>>>>>> anticipate a bit those needs in the KIP. > > >>>>>>>>>>>>>>>>>>>>>>>>> Thanks > > >>>>>>>>>>>>>>>>>>>>>>>>> Eno > > >>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>>> On 1 Feb 2017, at 10:18, Damian Guy < > > >>>>>>>>>> damian....@gmail.com> > > >>>>>>>>>>>>>>>>> wrote: > > >>>>>>>>>>>>>>>>>>>>>>>>>> Hi all, > > >>>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>>> I would like to start the discussion on > KIP-116: > > >>>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> https://cwiki.apache.org/ > confluence/display/KAFKA/KIP- > > >>>>>>>>>>>>>>>>> 116+-+Add+State+Store+Checkpoint+Interval+ > Configuration > > >>>>>>>>>>>>>>>>>>>>>>>>>> Thanks, > > >>>>>>>>>>>>>>>>>>>>>>>>>> Damian > > >>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>>>>>> > > >>>>>>>>>>>>>> > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> -- > > >>>>>>>>>>>>> -- Guozhang > > >>>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> > > >>>>>>>>>>>> -- > > >>>>>>>>>>>> -- Guozhang > > >>>>>>>>>>> > > >>>>>>>>>> > > >>>>>>>>>> -- > > >>>>>>>>>> -- Guozhang > > >>>>>>>>>> > > >>>>>>>> > > >>>>> > > >>>>> > > >>>>> DISCLAIMER > > >>>>> ========== > > >>>>> This e-mail may contain privileged and confidential information > which > > >> is > > >>>> the property of Persistent Systems Ltd. It is intended only for the > > use > > >> of > > >>>> the individual or entity to which it is addressed. If you are not > the > > >>>> intended recipient, you are not authorized to read, retain, copy, > > print, > > >>>> distribute or use this message. If you have received this > > communication > > >> in > > >>>> error, please notify the sender and delete all copies of this > message. > > >>>> Persistent Systems Ltd. does not accept any liability for virus > > infected > > >>>> mails. > > >>>>> > > >>>> > > >>>> > > >>> > > >>> > > >>> -- > > >>> -- Guozhang > > >> > > >> > > > > > > > > -- -- Guozhang
