Thanks Xintong! Just so I understand correctly, do you suggest adding a metric for delta(Time) / delta(Count) since the last reporting ? <Collector>.TimePerGc or <Collector>.AverageTime would make sense. AverageTime may be a bit nicer :)
My only concern is how useful this will be in reality. If there are only (or several) long pauses then the msPerSec metrics will show it already, and if there is a single long pause that may not be shown at all if there are several shorter pauses as well with this metric. Gyula On Wed, Sep 6, 2023 at 8:46 AM Xintong Song <tonysong...@gmail.com> wrote: > Thanks for bringing this up, Gyula. > > The proposed changes make sense to me. +1 for them. > > In addition to the proposed changes, I wonder if we should also add > something like timePerGc? This would help understand whether there are long > pauses, due to GC STW, that may lead to rpc unresponsiveness and heartbeat > timeouts. Ideally, we'd like to understand the max pause time per STW in a > recent time window. However, I don't see an easy way to separate the pause > time of each STW. Deriving the overall time per GC from the existing > metrics (time-increment / count-increment) seems to be a good alternative. > WDYT? > > Best, > > Xintong > > > > On Wed, Sep 6, 2023 at 2:16 PM Rui Fan <1996fan...@gmail.com> wrote: > > > Thanks for the clarification! > > > > By default the meterview measures for 1 minute sounds good to me! > > > > +1 for this proposal. > > > > Best, > > Rui > > > > On Wed, Sep 6, 2023 at 1:27 PM Gyula Fóra <gyula.f...@gmail.com> wrote: > > > > > Thanks for the feedback Rui, > > > > > > The rates would be computed using the MeterView class (like for any > other > > > rate metric), just because we report the value per second it doesn't > mean > > > that we measure in a second granularity. > > > By default the meterview measures for 1 minute and then we calculate > the > > > per second rates, but we can increase the timespan if necessary. > > > > > > So I don't think we run into this problem in practice and we can keep > the > > > metric aligned with other time rate metrics like busyTimeMsPerSec etc. > > > > > > Cheers, > > > Gyula > > > > > > On Wed, Sep 6, 2023 at 4:55 AM Rui Fan <1996fan...@gmail.com> wrote: > > > > > > > Hi Gyula, > > > > > > > > +1 for this proposal. The current GC metric is really unfriendly. > > > > > > > > I have a concern with your proposed rate metric: the rate is > perSecond > > > > instead of per minute. I'm unsure whether it's suitable for GC > metric. > > > > > > > > There are two reasons why I suspect perSecond may not be well > > > > compatible with GC metric: > > > > > > > > 1. GCs are usually infrequent and may only occur for a small number > > > > of time periods within a minute. > > > > > > > > Metrics are collected periodically, for example, reported every > minute. > > > > If the result reported by the GC metric is 1s/perSecond, it does not > > > > mean that the GC of the TM is serious, because there may be no GC > > > > in the remaining 59s. > > > > > > > > On the contrary, the GC metric reports 0s/perSecond, which does not > > > > mean that the GC of the TM is not serious, and the GC may be very > > > > serious in the remaining 59s. > > > > > > > > 2. Stop-the-world may cause the metric to fail(delay) to report > > > > > > > > The TM will stop the world during GC, especially full GC. It means > > > > the metric cannot be collected or reported during full GC. > > > > > > > > So the collected GC metric may never be 1s/perSecond. This metric > > > > may always be good because the metric will only be reported when > > > > the GC is not severe. > > > > > > > > > > > > If these concerns make sense, how about updating the GC rate > > > > at minute level? > > > > > > > > We can define the type to Gauge for TimeMsPerMiunte, and updating > > > > this Gauge every second, it is: > > > > GC Total.Time of current time - GC total time of one miunte ago. > > > > > > > > Best, > > > > Rui > > > > > > > > On Tue, Sep 5, 2023 at 11:05 PM Maximilian Michels <m...@apache.org> > > > wrote: > > > > > > > > > Hi Gyula, > > > > > > > > > > +1 The proposed changes make sense and are in line with what is > > > > > available for other metrics, e.g. number of records processed. > > > > > > > > > > -Max > > > > > > > > > > On Tue, Sep 5, 2023 at 2:43 PM Gyula Fóra <gyula.f...@gmail.com> > > > wrote: > > > > > > > > > > > > Hi Devs, > > > > > > > > > > > > I would like to start a discussion on FLIP-361: Improve GC > Metrics > > > [1]. > > > > > > > > > > > > The current Flink GC metrics [2] are not very useful for > monitoring > > > > > > purposes as they require post processing logic that is also > > dependent > > > > on > > > > > > the current runtime environment. > > > > > > > > > > > > Problems: > > > > > > - Total time is not very relevant for long running applications, > > > only > > > > > the > > > > > > rate of change (msPerSec) > > > > > > - In most cases it's best to simply aggregate the time/count > > across > > > > the > > > > > > different GabrageCollectors, however the specific collectors are > > > > > dependent > > > > > > on the current Java runtime > > > > > > > > > > > > We propose to improve the current situation by: > > > > > > - Exposing rate metrics per GarbageCollector > > > > > > - Exposing aggregated Total time/count/rate metrics > > > > > > > > > > > > These new metrics are all derived from the existing ones with > > minimal > > > > > > overhead. > > > > > > > > > > > > Looking forward to your feedback. > > > > > > > > > > > > Cheers, > > > > > > Gyula > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-361%3A+Improve+GC+Metrics > > > > > > [2] > > > > > > > > > > > > > > > > > > > > > https://nightlies.apache.org/flink/flink-docs-master/docs/ops/metrics/#garbagecollection > > > > > > > > > > > > > > >
