Woops! Thanks for the catch Lucas. Given this was just a typo, I don't think this affects the voting.
Cheers, Nick On Tue, 14 May 2024 at 18:06, Lucas Brutschy <lbruts...@confluent.io.invalid> wrote: > Hi Nick, > > you are still referring to oldest-open-iterator-age-ms in the > `Proposed Changes` section. > > Cheers, > Lucas > > On Thu, May 2, 2024 at 4:00 PM Lucas Brutschy <lbruts...@confluent.io> > wrote: > > > > Hi Nick! > > > > I agree, the age variant is a bit nicer since the semantics are very > > clear from the name. If you'd rather go for the simple implementation, > > how about calling it `oldest-iterator-open-since-ms`? I believe this > > could be understood without docs. Either way, I think we should be > > able to open the vote for this KIP because nobody raised any major / > > blocking concerns. > > > > Looking forward to getting this voted on soon! > > > > Cheers > > Lucas > > > > On Sun, Mar 31, 2024 at 5:23 PM Nick Telford <nick.telf...@gmail.com> > wrote: > > > > > > Hi Matthias, > > > > > > > For the oldest iterator metric, I would propose something simple like > > > > `iterator-opened-ms` and it would just be the actual timestamp when > the > > > > iterator was opened. I don't think we need to compute the actual age, > > > > but user can to this computation themselves? > > > > > > That works for me; it's easier to implement like that :-D I'm a little > > > concerned that the name "iterator-opened-ms" may not be obvious enough > > > without reading the docs. > > > > > > > If we think reporting the age instead of just the timestamp is > better, I > > > > would propose `iterator-max-age-ms`. I should be sufficient to call > out > > > > (as it's kinda "obvious" anyway) that the metric applies to open > > > > iterator only. > > > > > > While I think it's preferable to record the timestamp, rather than the > age, > > > this does have the benefit of a more obvious metric name. > > > > > > > Nit: the KIP says it's a store-level metric, but I think it would be > > > > good to say explicitly that it's recorded with DEBUG level only? > > > > > > Yes, I've already updated the KIP with this information in the table. > > > > > > Regards, > > > > > > Nick > > > > > > On Sun, 31 Mar 2024 at 10:53, Matthias J. Sax <mj...@apache.org> > wrote: > > > > > > > The time window thing was just an idea. Happy to drop it. > > > > > > > > For the oldest iterator metric, I would propose something simple like > > > > `iterator-opened-ms` and it would just be the actual timestamp when > the > > > > iterator was opened. I don't think we need to compute the actual age, > > > > but user can to this computation themselves? > > > > > > > > If we think reporting the age instead of just the timestamp is > better, I > > > > would propose `iterator-max-age-ms`. I should be sufficient to call > out > > > > (as it's kinda "obvious" anyway) that the metric applies to open > > > > iterator only. > > > > > > > > And yes, I was hoping that the code inside MetereXxxStore might > already > > > > be setup in a way that custom stores would inherit the iterator > metrics > > > > automatically -- I am just not sure, and left it as an exercise for > > > > somebody to confirm :) > > > > > > > > > > > > Nit: the KIP says it's a store-level metric, but I think it would be > > > > good to say explicitly that it's recorded with DEBUG level only? > > > > > > > > > > > > > > > > -Matthias > > > > > > > > > > > > On 3/28/24 2:52 PM, Nick Telford wrote: > > > > > Quick addendum: > > > > > > > > > > My suggested metric "oldest-open-iterator-age-seconds" should be > > > > > "oldest-open-iterator-age-ms". Milliseconds is obviously a better > > > > > granularity for such a metric. > > > > > > > > > > Still accepting suggestions for a better name. > > > > > > > > > > On Thu, 28 Mar 2024 at 13:41, Nick Telford <nick.telf...@gmail.com > > > > > > wrote: > > > > > > > > > >> Hi everyone, > > > > >> > > > > >> Sorry for leaving this for so long. So much for "3 weeks until KIP > > > > freeze"! > > > > >> > > > > >> On Sophie's comments: > > > > >> 1. Would Matthias's suggestion of a separate metric tracking the > age of > > > > >> the oldest open iterator (within the tag set) satisfy this? That > way we > > > > can > > > > >> keep iterator-duration-(avg|max) for closed iterators, which can > be > > > > useful > > > > >> for performance debugging for iterators that don't leak. I'm not > sure > > > > what > > > > >> we'd call this metric, maybe: "oldest-open-iterator-age-seconds"? > Seems > > > > >> like a mouthful. > > > > >> > > > > >> 2. You're right, it makes more sense to provide > > > > >> iterator-duration-(avg|max). Honestly, I can't remember why I had > > > > "total" > > > > >> before, or why I was computing a rate-of-change over it. > > > > >> > > > > >> 3, 4, 5, 6. Agreed, I'll make all those changes as suggested. > > > > >> > > > > >> 7. Combined with Matthias's point about RocksDB, I'm convinced > that this > > > > >> is the wrong KIP for these. I'll introduce the additional Rocks > metrics > > > > in > > > > >> another KIP. > > > > >> > > > > >> On Matthias's comments: > > > > >> A. Not sure about the time window. I'm pretty sure all existing > avg/max > > > > >> metrics are since the application was started? Any other > suggestions > > > > here > > > > >> would be appreciated. > > > > >> > > > > >> B. Agreed. See point 1 above. > > > > >> > > > > >> C. Good point. My focus was very much on Rocks memory leaks when > I wrote > > > > >> the first draft. I can generalise it. My only concern is that it > might > > > > make > > > > >> it more difficult to detect Rocks iterator leaks caused *within* > our > > > > >> high-level iterator, e.g. RocksJNI, RocksDB, RocksDBStore, etc. > But we > > > > >> could always provide a RocksDB-specific metric for this, as you > > > > suggested. > > > > >> > > > > >> D. Hmm, we do already have MeteredKeyValueIterator, which > automatically > > > > >> wraps the iterator from inner-stores of MeteredKeyValueStore. If > we > > > > >> implemented these metrics there, then custom stores would > automatically > > > > >> gain the functionality, right? This seems like a pretty logical > place to > > > > >> implement these metrics, since MeteredKeyValueStore is all about > adding > > > > >> metrics to state stores. > > > > >> > > > > >>> I imagine the best way to implement this would be to do so at the > > > > >>> high-level iterator rather than implementing it separately for > each > > > > >>> specific iterator implementation for every store type. > > > > >> > > > > >> Sophie, does MeteredKeyValueIterator fit with your recommendation? > > > > >> > > > > >> Thanks for your thoughts everyone, I'll update the KIP now. > > > > >> > > > > >> Nick > > > > >> > > > > >> On Thu, 14 Mar 2024 at 03:37, Sophie Blee-Goldman < > > > > sop...@responsive.dev> > > > > >> wrote: > > > > >> > > > > >>> About your last two points: I completely agree that we should > try to > > > > >>> make this independent of RocksDB, and should probably adopt a > > > > >>> general philosophy of being store-implementation agnostic unless > > > > >>> there is good reason to focus on a particular store type: eg if > it was > > > > >>> only possible to implement for certain stores, or only made > sense in > > > > >>> the context of a certain store type but not necessarily stores in > > > > general. > > > > >>> > > > > >>> While leaking memory due to unclosed iterators on RocksDB stores > is > > > > >>> certainly the most common issue, I think Matthias sufficiently > > > > >>> demonstrated that the problem of leaking iterators is not > actually > > > > >>> unique to RocksDB, and we should consider including in-memory > > > > >>> stores at the very least. I also think that at this point, we > may as > > > > well > > > > >>> just implement the metrics for *all* store types, whether > rocksdb or > > > > >>> in-memory or custom. Not just because it probably applies to all > > > > >>> store types (leaking iterators are rarely a good thing!) but > because > > > > >>> I imagine the best way to implement this would be to do so at the > > > > >>> high-level iterator rather than implementing it separately for > each > > > > >>> specific iterator implementation for every store type. > > > > >>> > > > > >>> That said, I haven't thought all that carefully about the > > > > implementation > > > > >>> yet -- it just strikes me as easiest to do at the top level of > the > > > > store > > > > >>> hierarchy rather than at the bottom. My gut instinct may very > well be > > > > >>> wrong, but that's what it's saying > > > > >>> > > > > >>> On Thu, Mar 7, 2024 at 10:43 AM Matthias J. Sax < > mj...@apache.org> > > > > wrote: > > > > >>> > > > > >>>> Seems I am late to this party. Can we pick this up again aiming > for > > > > 3.8 > > > > >>>> release? I think it would be a great addition. Few comments: > > > > >>>> > > > > >>>> > > > > >>>> - I think it does make sense to report `iterator-duration-avg` > and > > > > >>>> `iterator-duration-max` for all *closed* iterators -- it just > seems to > > > > >>>> be a useful metric (wondering if this would be _overall_ or > bounded to > > > > >>>> some time window?) > > > > >>>> > > > > >>>> - About the duration iterators are currently open, I believe > the only > > > > >>>> useful way is to report the "oldest iterator", ie, the smallest > > > > iterator > > > > >>>> open-time, of all currently open-iterator? We all agree that in > > > > general, > > > > >>>> leaking iterator would bump the count metric, and if there is a > few > > > > ones > > > > >>>> which are not closed and open for a long time, it seem > sufficient to > > > > >>>> detect the single oldest one for alerting purpose? > > > > >>>> > > > > >>>> - What I don't like about the KIP is it focus on RocksDB. I > don't > > > > think > > > > >>>> we should build on the internal RocksDB counters as proposed (I > guess, > > > > >>>> we could still expose them, similar to other RocksDB metrics > which we > > > > >>>> expose already). However, for this new metric, we should track > it > > > > >>>> ourselves and thus make it independent of RocksDB -- in the > end, an > > > > >>>> in-memory store could also leak memory (and kill a JVM with an > > > > >>>> out-of-memory error) and we should be able to track it. > > > > >>>> > > > > >>>> - Not sure if we would like to add support for custom stores, > to allow > > > > >>>> them to register their iterators with this metric? Or would > this not > > > > be > > > > >>>> necessary, because custom stores could just register a custom > metric > > > > >>>> about it to begin with? > > > > >>>> > > > > >>>> > > > > >>>> > > > > >>>> -Matthias > > > > >>>> > > > > >>>> On 10/25/23 4:41 PM, Sophie Blee-Goldman wrote: > > > > >>>>>> > > > > >>>>>> If we used "iterator-duration-max", for > > > > >>>>>> example, would it not be confusing that it includes Iterators > that > > > > >>> are > > > > >>>>>> still open, and therefore the duration is not yet known? > > > > >>>>> > > > > >>>>> > > > > >>>>> 1. Ah, I think I understand your concern better now -- I > totally > > > > agree > > > > >>>> that > > > > >>>>> a > > > > >>>>> "iterator-duration-max" metric would be > confusing/misleading. I > > > > was > > > > >>>>> thinking about it a bit differently, something more akin to the > > > > >>>>> "last-rebalance-seconds-ago" consumer metric. As the name > suggests, > > > > >>>>> that basically just tracks how long the consumer has gone > without > > > > >>>>> rebalancing -- it doesn't purport to represent the actual > duration > > > > >>>> between > > > > >>>>> rebalances, just the current time since the last one. The > hard part > > > > >>> is > > > > >>>>> really > > > > >>>>> in choosing a name that reflects this -- maybe you have some > better > > > > >>> ideas > > > > >>>>> but off the top of my head, perhaps something like > > > > >>>> "iterator-lifetime-max"? > > > > >>>>> > > > > >>>>> 2. I'm not quite sure how to interpret the > "iterator-duration-total" > > > > >>>> metric > > > > >>>>> -- what exactly does it mean to add up all the iterator > durations? > > > > For > > > > >>>>> some context, while this is not a hard-and-fast rule, in > general > > > > >>> you'll > > > > >>>>> find that Kafka/Streams metrics tend to come in pairs of > avg/max or > > > > >>>>> rate/total. Something that you might measure the avg for > usually is > > > > >>>>> also useful to measure the max, whereas a total metric is > probably > > > > >>>>> also useful as a rate but not so much as an avg. I actually > think > > > > this > > > > >>>>> is part of why it feels like it makes so much sense to include > a > > > > "max" > > > > >>>>> version of this metric, as Lucas suggested, even if the name of > > > > >>>>> "iterator-duration-max" feels misleading. Ultimately the > metric names > > > > >>>>> are up to you, but for this reason, I would personally > advocate for > > > > >>>>> just going with an "iterator-duration-avg" and > > > > "iterator-duration-max" > > > > >>>>> > > > > >>>>> I did see your example in which you mention one could monitor > the > > > > >>>>> rate of change of the "-total" metric. While this does make > sense to > > > > >>>>> me, if the only way to interpret a metric is by computing > another > > > > >>>>> function over it, then why not just make that computation the > metric > > > > >>>>> and cut out the middle man? And in this case, to me at least, > it > > > > feels > > > > >>>>> much easier to understand a metric like > "iterator-duration-max" vs > > > > >>>>> something like "iterator-duration-total-rate" > > > > >>>>> > > > > >>>>> 3. By the way, can you add another column to the table with > the new > > > > >>>> metrics > > > > >>>>> that lists the recording level? My suggestion would be to put > the > > > > >>>>> "number-open-iterators" at INFO and the other two at DEBUG. See > > > > >>>>> the following for my reasoning behind this recommendation > > > > >>>>> > > > > >>>>> 4. I would change the "Type" entry for the > "number-open-iterators" > > > > >>> from > > > > >>>>> "Value" to "Gauge". This helps justify the "INFO" level for > this > > > > >>> metric, > > > > >>>>> since unlike the other metrics which are "Measurables", the > current > > > > >>>>> timestamp won't need to be retrieved on each recording > > > > >>>>> > > > > >>>>> 5. Can you list the tags that would be associated with each of > these > > > > >>>>> metrics (either in the table, or separately above/below if > they will > > > > >>> be > > > > >>>>> the same for all) > > > > >>>>> > > > > >>>>> 6. Do you have a strong preference for the name > > > > >>> "number-open-iterators" > > > > >>>>> or would you be alright in shortening this to > "num-open-iterators"? > > > > >>> The > > > > >>>>> latter is more in line with the naming scheme used elsewhere > in Kafka > > > > >>>>> for similar kinds of metrics, and a shorter name is always > nice. > > > > >>>>> > > > > >>>>> 7. With respect to the rocksdb cache metrics, those sound > useful but > > > > >>>>> if it was me, I would probably save them for a separate KIP > mainly > > > > >>> just > > > > >>>>> because the KIP freeze deadline is in a few weeks, and I > wouldn't > > > > want > > > > >>>>> to end up blocking all the new metrics just because there was > ongoing > > > > >>>>> debate about a subset of them. That said, you do have 3 full > weeks, > > > > so > > > > >>>>> I would hope that you could get both sets of metrics agreed > upon in > > > > >>>>> that timeframe! > > > > >>>>> > > > > >>>>> > > > > >>>>> On Tue, Oct 24, 2023 at 6:35 AM Nick Telford < > nick.telf...@gmail.com > > > > > > > > > >>>> wrote: > > > > >>>>> > > > > >>>>>> I don't really have a problem with adding such a metric, I'm > just > > > > not > > > > >>>>>> entirely sure how it would work. If we used > "iterator-duration-max", > > > > >>> for > > > > >>>>>> example, would it not be confusing that it includes Iterators > that > > > > >>> are > > > > >>>>>> still open, and therefore the duration is not yet known? When > > > > >>> graphing > > > > >>>> that > > > > >>>>>> over time, I suspect it would be difficult to understand. > > > > >>>>>> > > > > >>>>>> 3. > > > > >>>>>> FWIW, this would still be picked up by "open-iterators", > since that > > > > >>>> metric > > > > >>>>>> is only decremented when Iterator#close is called (via the > > > > >>>>>> ManagedKeyValueIterator#onClose hook). > > > > >>>>>> > > > > >>>>>> I'm actually considering expanding the scope of this KIP > slightly to > > > > >>>>>> include improved Block Cache metrics, as my own memory leak > > > > >>>> investigations > > > > >>>>>> have trended in that direction. Do you think the following > metrics > > > > >>>> should > > > > >>>>>> be included in this KIP, or should I create a new KIP? > > > > >>>>>> > > > > >>>>>> - block-cache-index-usage (number of bytes occupied by > index > > > > >>> blocks) > > > > >>>>>> - block-cache-filter-usage (number of bytes occupied by > filter > > > > >>>> blocks) > > > > >>>>>> > > > > >>>>>> Regards, > > > > >>>>>> Nick > > > > >>>>>> > > > > >>>>>> On Tue, 24 Oct 2023 at 07:09, Sophie Blee-Goldman < > > > > >>>> sop...@responsive.dev> > > > > >>>>>> wrote: > > > > >>>>>> > > > > >>>>>>> I actually think we could implement Lucas' suggestion pretty > easily > > > > >>> and > > > > >>>>>>> without too much additional effort. We have full control > over the > > > > >>>>>> iterator > > > > >>>>>>> that is returned by the various range queries, so it would > be easy > > > > >>> to > > > > >>>>>>> register a gauge metric for how long it has been since the > iterator > > > > >>> was > > > > >>>>>>> created. Then we just deregister the metric when the > iterator is > > > > >>>> closed. > > > > >>>>>>> > > > > >>>>>>> With respect to how useful this metric would be, both Nick > and > > > > Lucas > > > > >>>> have > > > > >>>>>>> made good points: I would agree that in general, leaking > iterators > > > > >>>> would > > > > >>>>>>> mean an ever-increasing iterator count that should be > possible to > > > > >>> spot > > > > >>>>>>> without this. However, a few things to consider: > > > > >>>>>>> > > > > >>>>>>> 1. it's really easy to set up an alert based on some maximum > > > > >>> threshold > > > > >>>> of > > > > >>>>>>> how long an iterator should remain open for. It's relatively > more > > > > >>>> tricky > > > > >>>>>> to > > > > >>>>>>> set up alerts based on the current count of open iterators > and how > > > > >>> it > > > > >>>>>>> changes over time. > > > > >>>>>>> 2. As Lucas mentioned, it only takes a few iterators to > wreak havoc > > > > >>> in > > > > >>>>>>> extreme cases. Sometimes more advanced applications end up > with > > > > >>> just a > > > > >>>>>> few > > > > >>>>>>> leaking iterators despite closing the majority of them. I've > seen > > > > >>> this > > > > >>>>>>> happen just once personally, but it was driving everyone > crazy > > > > >>> until we > > > > >>>>>>> figured it out. > > > > >>>>>>> 3. A metric for how long the iterator has been open would > help to > > > > >>>>>> identify > > > > >>>>>>> hanging iterators due to some logic where the iterator is > properly > > > > >>>> closed > > > > >>>>>>> but for whatever reason just isn't being advanced to the > end, and > > > > >>> thus > > > > >>>>>> not > > > > >>>>>>> reached the iterator#close line of the user code. This case > seems > > > > >>>>>> difficult > > > > >>>>>>> to spot without the specific metric for iterator lifetime > > > > >>>>>>> 4. Lastly, I think you could argue that all of the above are > fairly > > > > >>>>>>> advanced use cases, but this seems like a fairly advanced > feature > > > > >>>>>> already, > > > > >>>>>>> so it doesn't seem unreasonable to try and cover all the > bases. > > > > >>>>>>> > > > > >>>>>>> All that said, my philosophy is that the KIP author gets the > final > > > > >>> word > > > > >>>>>> on > > > > >>>>>>> what to pull into scope as long as the proposal isn't harming > > > > anyone > > > > >>>>>>> without the extra feature/changes. So it's up to you Nick > -- just > > > > >>>> wanted > > > > >>>>>>> to add some context on how it could work, and why it would be > > > > >>> helpful > > > > >>>>>>> > > > > >>>>>>> Thanks for the KIP! > > > > >>>>>>> > > > > >>>>>>> On Wed, Oct 18, 2023 at 7:04 AM Lucas Brutschy > > > > >>>>>>> <lbruts...@confluent.io.invalid> wrote: > > > > >>>>>>> > > > > >>>>>>>> Hi Nick, > > > > >>>>>>>> > > > > >>>>>>>> I did not think in detail about how to implement it, just > about > > > > >>> what > > > > >>>>>>>> metrics would be nice to have. You are right, we'd have to > > > > >>>>>>>> register/deregister the iterators during open/close. This > would be > > > > >>>>>>>> more complicated to implement than the other metrics, but I > do not > > > > >>> see > > > > >>>>>>>> a fundamental problem with it. > > > > >>>>>>>> > > > > >>>>>>>> As far as I understand, even a low number of leaked > iterators can > > > > >>> hurt > > > > >>>>>>>> RocksDB compaction significantly. So we may even want to > detect if > > > > >>> the > > > > >>>>>>>> iterators are opened by one-time / rare queries against the > state > > > > >>>>>>>> store. > > > > >>>>>>>> > > > > >>>>>>>> But, as I said, that would be an addition and not a change > of the > > > > >>>>>>>> current contents of the KIP, so I'd support the KIP moving > forward > > > > >>>>>>>> even without this extension. > > > > >>>>>>>> > > > > >>>>>>>> Cheers, Lucas > > > > >>>>>>>> > > > > >>>>>>>> > > > > >>>>>>>> > > > > >>>>>>>> On Tue, Oct 17, 2023 at 3:45 PM Nick Telford < > > > > >>> nick.telf...@gmail.com> > > > > >>>>>>>> wrote: > > > > >>>>>>>>> > > > > >>>>>>>>> Hi Lucas, > > > > >>>>>>>>> > > > > >>>>>>>>> Hmm, I'm not sure how we could reliably identify such > leaked > > > > >>>>>> Iterators. > > > > >>>>>>>> If > > > > >>>>>>>>> we tried to include open iterators when calculating > > > > >>>>>> iterator-duration, > > > > >>>>>>>> we'd > > > > >>>>>>>>> need some kind of registry of all the open iterator > creation > > > > >>>>>>> timestamps, > > > > >>>>>>>>> wouldn't we? > > > > >>>>>>>>> > > > > >>>>>>>>> In general, if you have a leaky Iterator, it should > manifest as a > > > > >>>>>>>>> persistently climbing "open-iterators" metric, even on a > busy > > > > >>> node, > > > > >>>>>>>> because > > > > >>>>>>>>> each time that Iterator is used, it will leak another one. > So > > > > >>> even in > > > > >>>>>>> the > > > > >>>>>>>>> presence of many non-leaky Iterators on a busy instance, > the > > > > >>> metric > > > > >>>>>>>> should > > > > >>>>>>>>> still consistently climb. > > > > >>>>>>>>> > > > > >>>>>>>>> Regards, > > > > >>>>>>>>> > > > > >>>>>>>>> Nick > > > > >>>>>>>>> > > > > >>>>>>>>> On Mon, 16 Oct 2023 at 14:24, Lucas Brutschy < > > > > >>> lbruts...@confluent.io > > > > >>>>>>>> .invalid> > > > > >>>>>>>>> wrote: > > > > >>>>>>>>> > > > > >>>>>>>>>> Hi Nick! > > > > >>>>>>>>>> > > > > >>>>>>>>>> thanks for the KIP! I think this could be quite useful, > given > > > > the > > > > >>>>>>>>>> problems that we had with leaks due to RocksDB resources > not > > > > >>> being > > > > >>>>>>>>>> closed. > > > > >>>>>>>>>> > > > > >>>>>>>>>> I don't have any pressing issues why we can't accept it > like it > > > > >>> is, > > > > >>>>>>>>>> just one minor point for discussion: would it also make > sense to > > > > >>>>>> make > > > > >>>>>>>>>> it possible to identify a few very long-running / leaked > > > > >>>>>> iterators? I > > > > >>>>>>>>>> can imagine on a busy node, it would be hard to spot that > 1% of > > > > >>> the > > > > >>>>>>>>>> iterators never close when looking only at closed > iterator or > > > > the > > > > >>>>>>>>>> number of iterators. But it could still be good to > identify > > > > those > > > > >>>>>>>>>> leaks early. One option would be to add > `iterator-duration-max` > > > > >>> and > > > > >>>>>>>>>> take open iterators into account when computing the > metric. > > > > >>>>>>>>>> > > > > >>>>>>>>>> Cheers, > > > > >>>>>>>>>> Lucas > > > > >>>>>>>>>> > > > > >>>>>>>>>> > > > > >>>>>>>>>> On Thu, Oct 5, 2023 at 3:50 PM Nick Telford < > > > > >>>>>> nick.telf...@gmail.com> > > > > >>>>>>>>>> wrote: > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> Hi Colt, > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> I kept the details out of the KIP, because KIPs generally > > > > >>>>>> document > > > > >>>>>>>>>>> high-level design, but the way I'm doing it is like this: > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> final ManagedKeyValueIterator<Bytes, byte[]> > > > > >>>>>>>>>>> rocksDbPrefixSeekIterator = cf.prefixScan(accessor, > > > > >>> prefixBytes); > > > > >>>>>>>>>>> --> final long startedAt = System.nanoTime(); > > > > >>>>>>>>>>> openIterators.add(rocksDbPrefixSeekIterator); > > > > >>>>>>>>>>> rocksDbPrefixSeekIterator.onClose(() -> { > > > > >>>>>>>>>>> --> > > > > >>>>>>> metricsRecorder.recordIteratorDuration(System.nanoTime() > > > > >>>>>>>> - > > > > >>>>>>>>>>> startedAt); > > > > >>>>>>>>>>> > openIterators.remove(rocksDbPrefixSeekIterator); > > > > >>>>>>>>>>> }); > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> The lines with the arrow are the new code. This pattern > is > > > > >>>>>> repeated > > > > >>>>>>>>>>> throughout RocksDBStore, wherever a new RocksDbIterator > is > > > > >>>>>> created. > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> Regards, > > > > >>>>>>>>>>> Nick > > > > >>>>>>>>>>> > > > > >>>>>>>>>>> On Thu, 5 Oct 2023 at 12:32, Colt McNealy < > c...@littlehorse.io > > > > > > > > > >>>>>>>> wrote: > > > > >>>>>>>>>>> > > > > >>>>>>>>>>>> Thank you for the KIP, Nick! > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> This would be highly useful for many reasons. Much more > sane > > > > >>>>>> than > > > > >>>>>>>>>> checking > > > > >>>>>>>>>>>> for leaked iterators by profiling memory usage while > running > > > > >>>>>>> 100's > > > > >>>>>>>> of > > > > >>>>>>>>>>>> thousands of range scans via interactive queries (: > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> One small question: > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>>> The iterator-duration metrics will be updated whenever > an > > > > >>>>>>>> Iterator's > > > > >>>>>>>>>>>> close() method is called > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> Does the Iterator have its own "createdAt()" or > equivalent > > > > >>>>>> field, > > > > >>>>>>>> or > > > > >>>>>>>>>> do we > > > > >>>>>>>>>>>> need to keep track of the Iterator's start time upon > creation? > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> Cheers, > > > > >>>>>>>>>>>> Colt McNealy > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> *Founder, LittleHorse.dev* > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>> On Wed, Oct 4, 2023 at 9:07 AM Nick Telford < > > > > >>>>>>>> nick.telf...@gmail.com> > > > > >>>>>>>>>>>> wrote: > > > > >>>>>>>>>>>> > > > > >>>>>>>>>>>>> Hi everyone, > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> KIP-989 is a small Kafka Streams KIP to add a few new > metrics > > > > >>>>>>>> around > > > > >>>>>>>>>> the > > > > >>>>>>>>>>>>> creation and use of RocksDB Iterators, to aid users in > > > > >>>>>>>> identifying > > > > >>>>>>>>>>>>> "Iterator leaks" that could cause applications to leak > native > > > > >>>>>>>> memory. > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> Let me know what you think! > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>> > > > > >>>>>>>>>> > > > > >>>>>>>> > > > > >>>>>>> > > > > >>>>>> > > > > >>>> > > > > >>> > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-989%3A+RocksDB+Iterator+Metrics > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> P.S. I'm not too sure about the formatting of the "New > > > > >>>>>> Metrics" > > > > >>>>>>>>>> table, > > > > >>>>>>>>>>>> any > > > > >>>>>>>>>>>>> advice there would be appreciated. > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>>> Regards, > > > > >>>>>>>>>>>>> Nick > > > > >>>>>>>>>>>>> > > > > >>>>>>>>>>>> > > > > >>>>>>>>>> > > > > >>>>>>>> > > > > >>>>>>> > > > > >>>>>> > > > > >>>>> > > > > >>>> > > > > >>> > > > > >> > > > > > > > > > >