Anton, Seems like we have a name for the defragmentation mode with a downtime - Rolling Defrag )
- Denis On Mon, Oct 7, 2019 at 11:04 PM Anton Vinogradov <a...@apache.org> wrote: > Denis, > > I like the idea that defragmentation is just an additional step on a node > (re)start like we perform PDS recovery now. > We may just use special key to specify node should defragment persistence > on (re)start. > Defragmentation can be the part of Rolling Upgrade in this case :) > It seems to be not a problem to restart nodes one-by-one, this will "eat" > only one backup guarantee. > > On Mon, Oct 7, 2019 at 8:28 PM Denis Magda <dma...@apache.org> wrote: > > > Alex, thanks for the summary and proposal. Anton, Ivan and others who > took > > part in this discussion, what're your thoughts? I see this > > rolling-upgrades-based approach as a reasonable solution. Even though a > > node shutdown is expected, the procedure doesn't lead to the cluster > outage > > meaning it can be utilized for 24x7 production environments. > > > > - > > Denis > > > > > > On Mon, Oct 7, 2019 at 1:35 AM Alexey Goncharuk < > > alexey.goncha...@gmail.com> > > wrote: > > > > > Created a ticket for the first stage of this improvement. This can be a > > > first change towards the online mode suggested by Sergey and Anton. > > > https://issues.apache.org/jira/browse/IGNITE-12263 > > > > > > пт, 4 окт. 2019 г. в 19:38, Alexey Goncharuk < > alexey.goncha...@gmail.com > > >: > > > > > > > Maxim, > > > > > > > > Having a cluster-wide lock for a cache does not improve availability > of > > > > the solution. A user cannot defragment a cache if the cache is > involved > > > in > > > > a mission-critical operation, so having a lock on such a cache is > > > > equivalent to the whole cluster shutdown. > > > > > > > > We should decide between either a single offline node or a more > complex > > > > fully online solution. > > > > > > > > пт, 4 окт. 2019 г. в 11:55, Maxim Muzafarov <mmu...@apache.org>: > > > > > > > >> Igniters, > > > >> > > > >> This thread seems to be endless, but we if some kind of cache group > > > >> distributed write lock (exclusive for some of the internal Ignite > > > >> process) will be introduced? I think it will help to solve a batch > of > > > >> problems, like: > > > >> > > > >> 1. defragmentation of all cache group partitions on the local node > > > >> without concurrent updates. > > > >> 2. improve data loading with data streamer isolation mode [1]. It > > > >> seems we should not allow concurrent updates to cache if we on `fast > > > >> data load` step. > > > >> 3. recovery from a snapshot without cache stop\start actions > > > >> > > > >> > > > >> [1] https://issues.apache.org/jira/browse/IGNITE-11793 > > > >> > > > >> On Thu, 3 Oct 2019 at 22:50, Sergey Kozlov <skoz...@gridgain.com> > > > wrote: > > > >> > > > > >> > Hi > > > >> > > > > >> > I'm not sure that node offline is a best way to do that. > > > >> > Cons: > > > >> > - different caches may have different defragmentation but we > force > > to > > > >> stop > > > >> > whole node > > > >> > - offline node is a maintenance operation will require to add +1 > > > >> backup to > > > >> > reduce the risk of data loss > > > >> > - baseline auto adjustment? > > > >> > - impact to index rebuild? > > > >> > - cache configuration changes (or destroy) during node offline > > > >> > > > > >> > What about other ways without node stop? E.g. make cache group on > a > > > node > > > >> > offline? Add *defrag <cache_group> *command to control.sh to force > > > start > > > >> > rebalance internally in the node with expected impact to > > performance. > > > >> > > > > >> > > > > >> > > > > >> > On Thu, Oct 3, 2019 at 12:08 PM Anton Vinogradov <a...@apache.org> > > > wrote: > > > >> > > > > >> > > Alexey, > > > >> > > As for me, it does not matter will it be IEP, umbrella or a > single > > > >> issue. > > > >> > > The most important thing is Assignee :) > > > >> > > > > > >> > > On Thu, Oct 3, 2019 at 11:59 AM Alexey Goncharuk < > > > >> > > alexey.goncha...@gmail.com> > > > >> > > wrote: > > > >> > > > > > >> > > > Anton, do you think we should file a single ticket for this or > > > >> should we > > > >> > > go > > > >> > > > with an IEP? As of now, the change does not look big enough > for > > an > > > >> IEP > > > >> > > for > > > >> > > > me. > > > >> > > > > > > >> > > > чт, 3 окт. 2019 г. в 11:18, Anton Vinogradov <a...@apache.org>: > > > >> > > > > > > >> > > > > Alexey, > > > >> > > > > > > > >> > > > > Sounds good to me. > > > >> > > > > > > > >> > > > > On Thu, Oct 3, 2019 at 10:51 AM Alexey Goncharuk < > > > >> > > > > alexey.goncha...@gmail.com> > > > >> > > > > wrote: > > > >> > > > > > > > >> > > > > > Anton, > > > >> > > > > > > > > >> > > > > > Switching a partition to and from the SHRINKING state will > > > >> require > > > >> > > > > > intricate synchronizations in order to properly determine > > the > > > >> start > > > >> > > > > > position for historical rebalance without PME. > > > >> > > > > > > > > >> > > > > > I would still go with an offline-node approach, but > instead > > of > > > >> > > cleaning > > > >> > > > > the > > > >> > > > > > persistence, we can do effective defragmentation when the > > node > > > >> is > > > >> > > > offline > > > >> > > > > > because we are sure that there is no concurrent load. > After > > > the > > > >> > > > > > defragmentation completes, we bring the node back to the > > > >> cluster and > > > >> > > > > > historical rebalance will kick in automatically. It will > > still > > > >> > > require > > > >> > > > > > manual node restarts, but since the data is not removed, > > there > > > >> are no > > > >> > > > > > additional risks. Also, this will be an excellent solution > > for > > > >> those > > > >> > > > who > > > >> > > > > > can afford downtime and execute the defragment command on > > all > > > >> nodes > > > >> > > in > > > >> > > > > the > > > >> > > > > > cluster simultaneously - this will be the fastest way > > > possible. > > > >> > > > > > > > > >> > > > > > --AG > > > >> > > > > > > > > >> > > > > > пн, 30 сент. 2019 г. в 09:29, Anton Vinogradov < > > a...@apache.org > > > >: > > > >> > > > > > > > > >> > > > > > > Alexei, > > > >> > > > > > > >> stopping fragmented node and removing partition data, > > > then > > > >> > > > starting > > > >> > > > > it > > > >> > > > > > > again > > > >> > > > > > > > > > >> > > > > > > That's exactly what we're doing to solve the > fragmentation > > > >> issue. > > > >> > > > > > > The problem here is that we have to perform N/B > > > >> restart-rebalance > > > >> > > > > > > operations (N - cluster size, B - backups count) and it > > > takes > > > >> a lot > > > >> > > > of > > > >> > > > > > time > > > >> > > > > > > with risks to lose the data. > > > >> > > > > > > > > > >> > > > > > > On Fri, Sep 27, 2019 at 5:49 PM Alexei Scherbakov < > > > >> > > > > > > alexey.scherbak...@gmail.com> wrote: > > > >> > > > > > > > > > >> > > > > > > > Probably this should be allowed to do using public > API, > > > >> actually > > > >> > > > this > > > >> > > > > > is > > > >> > > > > > > > same as manual rebalancing. > > > >> > > > > > > > > > > >> > > > > > > > пт, 27 сент. 2019 г. в 17:40, Alexei Scherbakov < > > > >> > > > > > > > alexey.scherbak...@gmail.com>: > > > >> > > > > > > > > > > >> > > > > > > > > The poor man's solution for the problem would be > > > stopping > > > >> > > > > fragmented > > > >> > > > > > > node > > > >> > > > > > > > > and removing partition data, then starting it again > > > >> allowing > > > >> > > full > > > >> > > > > > state > > > >> > > > > > > > > transfer already without deletes. > > > >> > > > > > > > > Rinse and repeat for all owners. > > > >> > > > > > > > > > > > >> > > > > > > > > Anton Vinogradov, would this work for you as > > workaround > > > ? > > > >> > > > > > > > > > > > >> > > > > > > > > чт, 19 сент. 2019 г. в 13:03, Anton Vinogradov < > > > >> a...@apache.org > > > >> > > >: > > > >> > > > > > > > > > > > >> > > > > > > > >> Alexey, > > > >> > > > > > > > >> > > > >> > > > > > > > >> Let's combine your and Ivan's proposals. > > > >> > > > > > > > >> > > > >> > > > > > > > >> >> vacuum command, which acquires exclusive table > > lock, > > > >> so no > > > >> > > > > > > concurrent > > > >> > > > > > > > >> activities on the table are possible. > > > >> > > > > > > > >> and > > > >> > > > > > > > >> >> Could the problem be solved by stopping a node > > which > > > >> needs > > > >> > > to > > > >> > > > > be > > > >> > > > > > > > >> defragmented, clearing persistence files and > > restarting > > > >> the > > > >> > > > node? > > > >> > > > > > > > >> >> After rebalancing the node will receive all data > > > back > > > >> > > without > > > >> > > > > > > > >> fragmentation. > > > >> > > > > > > > >> > > > >> > > > > > > > >> How about to have special partition state > SHRINKING? > > > >> > > > > > > > >> This state should mean that partition unavailable > for > > > >> reads > > > >> > > and > > > >> > > > > > > updates > > > >> > > > > > > > >> but > > > >> > > > > > > > >> should keep it's update-counters and should not be > > > >> marked as > > > >> > > > lost, > > > >> > > > > > > > renting > > > >> > > > > > > > >> or evicted. > > > >> > > > > > > > >> At this state we able to iterate over the partition > > and > > > >> apply > > > >> > > > it's > > > >> > > > > > > > entries > > > >> > > > > > > > >> to another file in a compact way. > > > >> > > > > > > > >> Indices should be updated during the copy-on-shrink > > > >> procedure > > > >> > > or > > > >> > > > > at > > > >> > > > > > > the > > > >> > > > > > > > >> shrink completion. > > > >> > > > > > > > >> Once shrank file is ready we should replace the > > > original > > > >> > > > partition > > > >> > > > > > > file > > > >> > > > > > > > >> with it and mark it as MOVING which will start the > > > >> historical > > > >> > > > > > > rebalance. > > > >> > > > > > > > >> Shrinking should be performed during the low > activity > > > >> periods, > > > >> > > > but > > > >> > > > > > > even > > > >> > > > > > > > in > > > >> > > > > > > > >> case we found that activity was high and historical > > > >> rebalance > > > >> > > is > > > >> > > > > not > > > >> > > > > > > > >> suitable we may just remove the file and use > regular > > > >> rebalance > > > >> > > > to > > > >> > > > > > > > restore > > > >> > > > > > > > >> the partition (this will also lead to shrink). > > > >> > > > > > > > >> > > > >> > > > > > > > >> BTW, seems, we able to implement partition shrink > in > > a > > > >> cheap > > > >> > > > way. > > > >> > > > > > > > >> We may just use rebalancing code to apply fat > > > partition's > > > >> > > > entries > > > >> > > > > to > > > >> > > > > > > the > > > >> > > > > > > > >> new file. > > > >> > > > > > > > >> So, 3 stages here: local rebalance, indices update > > and > > > >> global > > > >> > > > > > > historical > > > >> > > > > > > > >> rebalance. > > > >> > > > > > > > >> > > > >> > > > > > > > >> On Thu, Sep 19, 2019 at 11:43 AM Alexey Goncharuk < > > > >> > > > > > > > >> alexey.goncha...@gmail.com> wrote: > > > >> > > > > > > > >> > > > >> > > > > > > > >> > Anton, > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > > >> The solution which Anton suggested does not > > > look > > > >> easy > > > >> > > > > > because > > > >> > > > > > > it > > > >> > > > > > > > >> will > > > >> > > > > > > > >> > > most likely significantly hurt performance > > > >> > > > > > > > >> > > Mostly agree here, but what drop do we expect? > > What > > > >> price > > > >> > > do > > > >> > > > > we > > > >> > > > > > > > ready > > > >> > > > > > > > >> to > > > >> > > > > > > > >> > > pay? > > > >> > > > > > > > >> > > Not sure, but seems some vendors ready to pay, > > for > > > >> > > example, > > > >> > > > 5% > > > >> > > > > > > drop > > > >> > > > > > > > >> for > > > >> > > > > > > > >> > > this. > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > 5% may be a big drop for some use-cases, so I > think > > > we > > > >> > > should > > > >> > > > > look > > > >> > > > > > > at > > > >> > > > > > > > >> how > > > >> > > > > > > > >> > to improve performance, not how to make it worse. > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > > > > > >> > > > > > > > >> > > >> it is hard to maintain a data structure to > > > choose > > > >> "page > > > >> > > > > from > > > >> > > > > > > > >> free-list > > > >> > > > > > > > >> > > with enough space closest to the beginning of > the > > > >> file". > > > >> > > > > > > > >> > > We can just split each free-list bucket to the > > > >> couple and > > > >> > > > use > > > >> > > > > > > first > > > >> > > > > > > > >> for > > > >> > > > > > > > >> > > pages in the first half of the file and the > > second > > > >> for the > > > >> > > > > last. > > > >> > > > > > > > >> > > Only two buckets required here since, during > the > > > file > > > >> > > > shrink, > > > >> > > > > > > first > > > >> > > > > > > > >> > > bucket's window will be shrank too. > > > >> > > > > > > > >> > > Seems, this give us the same price on put, just > > use > > > >> the > > > >> > > > first > > > >> > > > > > > bucket > > > >> > > > > > > > >> in > > > >> > > > > > > > >> > > case it's not empty. > > > >> > > > > > > > >> > > Remove price (with merge) will be increased, of > > > >> course. > > > >> > > > > > > > >> > > > > > >> > > > > > > > >> > > The compromise solution is to have priority put > > (to > > > >> the > > > >> > > > first > > > >> > > > > > path > > > >> > > > > > > > of > > > >> > > > > > > > >> the > > > >> > > > > > > > >> > > file), with keeping removal as is, and > > schedulable > > > >> > > per-page > > > >> > > > > > > > migration > > > >> > > > > > > > >> for > > > >> > > > > > > > >> > > the rest of the data during the low activity > > > period. > > > >> > > > > > > > >> > > > > > >> > > > > > > > >> > Free lists are large and slow by themselves, it > is > > > >> expensive > > > >> > > > to > > > >> > > > > > > > >> checkpoint > > > >> > > > > > > > >> > and read them on start, so as a long-term > solution > > I > > > >> would > > > >> > > > look > > > >> > > > > > into > > > >> > > > > > > > >> > removing them. Moreover, not sure if adding yet > > > another > > > >> > > > > background > > > >> > > > > > > > >> process > > > >> > > > > > > > >> > will improve the codebase reliability and > > simplicity. > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > If we want to go the hard path, I would look at > > free > > > >> page > > > >> > > > > tracking > > > >> > > > > > > > >> bitmap - > > > >> > > > > > > > >> > a special bitmask page, where each page in an > > > adjacent > > > >> block > > > >> > > > is > > > >> > > > > > > marked > > > >> > > > > > > > >> as 0 > > > >> > > > > > > > >> > if it has free space more than a certain > > configurable > > > >> > > > threshold > > > >> > > > > > > (say, > > > >> > > > > > > > >> 80%) > > > >> > > > > > > > >> > - free, and 1 if less (full). Some vendors have > > > >> successfully > > > >> > > > > > > > implemented > > > >> > > > > > > > >> > this approach, which looks much more promising, > but > > > >> harder > > > >> > > to > > > >> > > > > > > > implement. > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > --AG > > > >> > > > > > > > >> > > > > >> > > > > > > > >> > > > >> > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > -- > > > >> > > > > > > > > > > > >> > > > > > > > > Best regards, > > > >> > > > > > > > > Alexei Scherbakov > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > -- > > > >> > > > > > > > > > > >> > > > > > > > Best regards, > > > >> > > > > > > > Alexei Scherbakov > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > > >> > -- > > > >> > Sergey Kozlov > > > >> > GridGain Systems > > > >> > www.gridgain.com > > > >> > > > > > > > > > >
