Sorry for the lag but since we've got a consensus days ago, I started a vote thread which will have a result by EOD, thus I'm closing this discussion thread. Thanks all for the participation and comments/suggestions!
Best Regards, Yu On Fri, 16 Aug 2019 at 09:09, Till Rohrmann <trohrm...@apache.org> wrote: > +1 for this FLIP and the feature. I think this feature will be super > helpful for many Flink users. > > Once the SpillableHeapKeyedStateBackend has proven to be superior to the > HeapKeyedStateBackend we should think about removing the latter completely > to reduce maintenance burden. > > Cheers, > Till > > On Fri, Aug 16, 2019 at 4:06 AM Congxian Qiu <qcx978132...@gmail.com> > wrote: > > > Big +1 for this feature. > > > > This FLIP can help improves at least the following two scenarios: > > - Temporary data peak when using Heap StateBackend > > - Heap State Backend has better performance than RocksDBStateBackend, > > especially on SATA disk. there are some guys ever told me that they > > increased the parallelism of operators(and use HeapStateBackend) other > than > > use RocksDBStateBackend to get better performance. But increase > parallelism > > will have some other problems, after this FLIP, we can run Flink Job with > > the same parallelism as RocksDBStateBackend and get better performance > > also. > > > > Best, > > Congxian > > > > > > Yu Li <car...@gmail.com> 于2019年8月16日周五 上午12:14写道： > > > > > Thanks all for the reviews and comments! > > > > > > bq. From the implementation plan, it looks like this exists purely in a > > new > > > module and does not require any changes in other parts of Flink's code. > > Can > > > you confirm that? > > > Confirmed, thanks! > > > > > > Best Regards, > > > Yu > > > > > > > > > On Thu, 15 Aug 2019 at 18:04, Tzu-Li (Gordon) Tai <tzuli...@apache.org > > > > > wrote: > > > > > > > +1 to start a VOTE for this FLIP. > > > > > > > > Given the properties of this new state backend and that it will exist > > as > > > a > > > > new module without touching the original heap backend, I don't see a > > harm > > > > in including this. > > > > Regarding design of the feature, I've already mentioned my comments > in > > > the > > > > original discussion thread. > > > > > > > > Cheers, > > > > Gordon > > > > > > > > On Thu, Aug 15, 2019 at 5:53 PM Yun Tang <myas...@live.com> wrote: > > > > > > > > > Big +1 for this feature. > > > > > > > > > > Our customers including me, have ever met dilemma where we have to > > use > > > > > window to aggregate events in applications like real-time > monitoring. > > > The > > > > > larger of timer and window state, the poor performance of RocksDB. > > > > However, > > > > > switching to use FsStateBackend would always make me feel fear > about > > > the > > > > > OOM errors. > > > > > > > > > > Look forward for more powerful enrichment to state-backend, and > help > > > > Flink > > > > > to achieve better performance together. > > > > > > > > > > Best > > > > > Yun Tang > > > > > ________________________________ > > > > > From: Stephan Ewen <se...@apache.org> > > > > > Sent: Thursday, August 15, 2019 23:07 > > > > > To: dev <dev@flink.apache.org> > > > > > Subject: Re: [DISCUSS] FLIP-50: Spill-able Heap Keyed State Backend > > > > > > > > > > +1 for this feature. I think this will be appreciated by users, as > a > > > way > > > > to > > > > > use the HeapStateBackend with a safety-net against OOM errors. > > > > > And having had major production exposure is great. > > > > > > > > > > From the implementation plan, it looks like this exists purely in a > > new > > > > > module and does not require any changes in other parts of Flink's > > code. > > > > Can > > > > > you confirm that? > > > > > > > > > > Other that that, I have no further questions and we could proceed > to > > > vote > > > > > on this FLIP, from my side. > > > > > > > > > > Best, > > > > > Stephan > > > > > > > > > > > > > > > On Tue, Aug 13, 2019 at 10:00 PM Yu Li <car...@gmail.com> wrote: > > > > > > > > > > > Sorry for forgetting to give the link of the FLIP, here it is: > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-50%3A+Spill-able+Heap+Keyed+State+Backend > > > > > > > > > > > > Thanks! > > > > > > > > > > > > Best Regards, > > > > > > Yu > > > > > > > > > > > > > > > > > > On Tue, 13 Aug 2019 at 18:06, Yu Li <car...@gmail.com> wrote: > > > > > > > > > > > > > Hi All, > > > > > > > > > > > > > > We ever held a discussion about this feature before [1] but now > > > > opening > > > > > > > another thread because after a second thought introducing a new > > > > backend > > > > > > > instead of modifying the existing heap backend is a better > option > > > to > > > > > > > prevent causing any regression or surprise to existing > > > in-production > > > > > > usage. > > > > > > > And since introducing a new backend is relatively big change, > we > > > > regard > > > > > > it > > > > > > > as a FLIP and need another discussion and voting process > > according > > > to > > > > > our > > > > > > > newly drafted bylaw [2]. > > > > > > > > > > > > > > Please allow me to quote the brief description from the old > > thread > > > > [1] > > > > > > for > > > > > > > the convenience of those who noticed this feature for the first > > > time: > > > > > > > > > > > > > > > > > > > > > *HeapKeyedStateBackend is one of the two KeyedStateBackends in > > > Flink, > > > > > > > since state lives as Java objects on the heap in > > > > HeapKeyedStateBackend > > > > > > and > > > > > > > the de/serialization only happens during state snapshot and > > > restore, > > > > it > > > > > > > outperforms RocksDBKeyeStateBackend when all data could reside > in > > > > > > memory.**However, > > > > > > > along with the advantage, HeapKeyedStateBackend also has its > > > > > > shortcomings, > > > > > > > and the most painful one is the difficulty to estimate the > > maximum > > > > heap > > > > > > > size (Xmx) to set, and we will suffer from GC impact once the > > heap > > > > > memory > > > > > > > is not enough to hold all state data. There’re several > > (inevitable) > > > > > > causes > > > > > > > for such scenario, including (but not limited to):* > > > > > > > > > > > > > > > > > > > > > > > > > > > > ** Memory overhead of Java object representation (tens of times > > of > > > > the > > > > > > > serialized data size).* Data flood caused by burst traffic.* > Data > > > > > > > accumulation caused by source malfunction.**To resolve this > > > problem, > > > > we > > > > > > > proposed a solution to support spilling state data to disk > before > > > > heap > > > > > > > memory is exhausted. We will monitor the heap usage and choose > > the > > > > > > coldest > > > > > > > data to spill, and reload them when heap memory is regained > after > > > > data > > > > > > > removing or TTL expiration, automatically. Furthermore, *to > > prevent > > > > > > > causing unexpected regression to existing usage of > > > > > HeapKeyedStateBackend, > > > > > > > we plan to introduce a new SpillableHeapKeyedStateBackend and > > > change > > > > it > > > > > > to > > > > > > > default in future if proven to be stable. > > > > > > > > > > > > > > Please let us know your point of the feature and any comment is > > > > > > > welcomed/appreciated. Thanks. > > > > > > > > > > > > > > [1] https://s.apache.org/pxeif > > > > > > > [2] > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=120731026 > > > > > > > > > > > > > > Best Regards, > > > > > > > Yu > > > > > > > > > > > > > > > > > > > > > > > > > > > >
