+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 > > > > > > > > > > > > > > > > > > > > >
