In older versions of Apache Ignite, WAL archive could contain valid records needed for recovery. If something was changed since then, my comment may be not valid.
We've discussed that before, that naming this directory as 'archive' was not the best possible option. The archive is often considered by users as something not needed and sometimes it was deleted. See also page related to internals and directory structure: https://cwiki.apache.org/confluence/display/IGNITE/Ignite+Persistent+Store+-+under+the+hood#IgnitePersistentStoreunderthehood-WALstructure So infinite storage of archive is definitely not necessary for vanilla open-source version, but archive itself is needed. Sincerely, Dmitriy Pavlov ср, 11 нояб. 2020 г. в 01:21, Raymond Wilson <raymond_wil...@trimble.com>: > Isn't the discussion here related to the WAL archive? If you disable that > don't you still have the WAL containing un-checkpointed changes? > > On Wed, Nov 11, 2020 at 11:01 AM Dmitriy Pavlov <dpav...@apache.org> > wrote: > > > Hi Denis, > > > > the short answer here, Apache Ignite guarantees ACID, and for > D-Durability > > it is required to save all changes in some WAL/Redo Log to have a safe > way > > to recover from any hardware failures/disk outage. > > > > Should the user disable WAL, he/she could potentially lose durability. > > > > Sincerely, > > Dmitriy Pavlov > > > > вт, 10 нояб. 2020 г. в 09:57, ткаленко кирилл <tkalkir...@yandex.ru>: > > > > > Hello guys again! > > > > > > Does anyone know why we are doing any calculation here > > > IgniteUtils#adjustedWalHistorySize at all? > > > Would it be easier to always take the > > > DataStorageConfiguration#maxWalArchiveSize? It seems that the user can > > > easily do this himself by changing the value by 1 byte. > > > > > > 06.11.2020, 13:56, "Ivan Daschinsky" <ivanda...@gmail.com>: > > > > Alex, thanks for pointing that out. Shame that I missed it. > > > > > > > > пт, 6 нояб. 2020 г. в 13:45, Alex Plehanov <plehanov.a...@gmail.com > >: > > > > > > > >> Guys, > > > >> > > > >> We already have > > FileWriteAheadLogManager#maxSegCountWithoutCheckpoint. > > > >> Checkpoint triggered if there are too many WAL segments without > > > checkpoint. > > > >> Looks like you are talking about this feature. > > > >> > > > >> пт, 6 нояб. 2020 г. в 13:21, Ivan Daschinsky <ivanda...@gmail.com > >: > > > >> > > > >> > Kirill and I discussed privately proposed approach. As far as I > > > >> understand, > > > >> > Kirill suggests to implement some > > > >> > heuristic to do a force checkpoint in some cases if user by > mistake > > > >> > misconfigured cluster in order to preserve > > > >> > requested size of WAL archive. > > > >> > Currently, as for me, this approach is questionable, because it > can > > > cause > > > >> > some performance problems. But as an option, > > > >> > it can be used and should be switchable. > > > >> > > > > >> > пт, 6 нояб. 2020 г. в 12:36, Ivan Daschinsky < > ivanda...@gmail.com > > >: > > > >> > > > > >> > > Kirill, how your approach will help if user tuned a cluster to > do > > > >> > > checkpoints rarely under load? > > > >> > > No way. > > > >> > > > > > >> > > пт, 6 нояб. 2020 г. в 12:19, ткаленко кирилл < > > tkalkir...@yandex.ru > > > >: > > > >> > > > > > >> > >> Ivan, I agree with you that the archive is primarily about > > > >> optimization. > > > >> > >> > > > >> > >> If the size of the archive is critical for the user, we have > no > > > >> > >> protection against this, we can always go beyond this limit. > > > >> > >> Thus, the user needs to remember this and configure it in some > > > way. > > > >> > >> > > > >> > >> I suggest not to exceed this limit and give the expected > > behavior > > > for > > > >> > the > > > >> > >> user. At the same time, the segments needed for recovery will > > > remain > > > >> and > > > >> > >> there will be no data loss. > > > >> > >> > > > >> > >> 06.11.2020, 11:29, "Ivan Daschinsky" <ivanda...@gmail.com>: > > > >> > >> > Guys, fisrt of all, archiving is not for PITR at all, this > is > > > >> > >> optimization. > > > >> > >> > If we disable archiving, every rollover we need to create > new > > > file. > > > >> If > > > >> > >> we > > > >> > >> > enable archiving, we reserve 10 (by default) segments filled > > > with > > > >> > >> zeroes. > > > >> > >> > We use mmap by default, so if we use no-archiver approach: > > > >> > >> > 1. We firstly create new empty file > > > >> > >> > 2. Call on it sun.nio.ch.FileChannelImpl#map, thats under > the > > > hood > > > >> > >> > a. If file is shorter, than wal segment size, it > > > >> > >> > calls sun.nio.ch.FileDispatcherImpl#truncate0, this is under > > the > > > >> hood > > > >> > >> just > > > >> > >> > a system call truncate [1] > > > >> > >> > b. Than it calls system call mmap on this > > > >> > >> > file sun.nio.ch.FileChannelImpl#map0, under the hood see [2] > > > >> > >> > These manipulation are not free and cheap. So rollover will > be > > > much > > > >> > much > > > >> > >> > slower. > > > >> > >> > If archiving is enabled, 10 segments are already > preallocated > > > at the > > > >> > >> moment > > > >> > >> > of node's start. > > > >> > >> > > > > >> > >> > When archiving is enabled, archiver just copy previous > > > preallocated > > > >> > >> segment > > > >> > >> > and move it to archive directory. > > > >> > >> > This archived segment is crucial for recovery. When new > > > checkpoints > > > >> > >> > finished, all eligible for trunocating segments are just > > > removed. > > > >> > >> > > > > >> > >> > If archiving is disabled, we also write WAL segments in wal > > > >> directory > > > >> > >> and > > > >> > >> > disabling archiving don't prevent you from storing segments, > > if > > > they > > > >> > are > > > >> > >> > required for recovery. > > > >> > >> > > > > >> > >> >>> Before increasing the size of WAL archive (transferring to > > > archive > > > >> > >> > > > > >> > >> > /rollOver, compression, decompression), we can make sure > that > > > there > > > >> > >> will be > > > >> > >> > enough space in the archive and if there is no such, then we > > > will > > > >> try > > > >> > to > > > >> > >> >>> clean it. We cannot delete those segments that are > required > > > for > > > >> > >> recovery > > > >> > >> > > > > >> > >> > (between the last two checkpoints) and reserved for example > > for > > > >> > >> historical > > > >> > >> > rebalancing. > > > >> > >> > First of all, compression/decompression is offtopic here. > > > >> > >> > Secondly, wal segments are required only with idx higher > than > > > LAST > > > >> > >> > checkpoint marker. > > > >> > >> > Thirdly, archiving and rolling over can be during checkpoint > > > and we > > > >> > can > > > >> > >> > broke everything accidentially. > > > >> > >> > Fourthly, I see no benefits to overcomplicated already > > > complicated > > > >> > >> logic. > > > >> > >> > This is basically problem of misunderstanding and tuning. > > > >> > >> > There are a lot of similar topics for almost every DB. [3] > > > >> > >> > > > > >> > >> > [1] -- > https://man7.org/linux/man-pages/man2/ftruncate.2.html > > > >> > >> > [2] -- https://man7.org/linux/man-pages/man2/mmap.2.html > > > >> > >> > [3] -- > > > >> > >> > > > > >> > >> > > > >> > > > > >> > > > > > > https://www.google.com/search?q=pg_wal%2Fxlogtemp+no+space+left+on+device&oq=pg+wal+no > > > >> > >> > > > > >> > >> > пт, 6 нояб. 2020 г. в 10:42, ткаленко кирилл < > > > tkalkir...@yandex.ru > > > >> >: > > > >> > >> > > > > >> > >> >> Hi, Ivan! > > > >> > >> >> > > > >> > >> >> I have only described ideas. But here are a few more > details. > > > >> > >> >> > > > >> > >> >> We can take care not to go beyond > > > >> > >> >> DataStorageConfiguration#maxWalArchiveSize. > > > >> > >> >> > > > >> > >> >> Before increasing the size of WAL archive (transferring to > > > archive > > > >> > >> >> /rollOver, compression, decompression), we can make sure > that > > > >> there > > > >> > >> will be > > > >> > >> >> enough space in the archive and if there is no such, then > we > > > will > > > >> > try > > > >> > >> to > > > >> > >> >> clean it. We cannot delete those segments that are required > > for > > > >> > >> recovery > > > >> > >> >> (between the last two checkpoints) and reserved for example > > for > > > >> > >> historical > > > >> > >> >> rebalancing. > > > >> > >> >> > > > >> > >> >> We can receive a notification about the change of > checkpoints > > > and > > > >> > the > > > >> > >> >> reservation / release of segments, thus we can know how > many > > > >> > segments > > > >> > >> we > > > >> > >> >> can delete right now. > > > >> > >> >> > > > >> > >> >> 06.11.2020, 09:53, "Ivan Daschinsky" <ivanda...@gmail.com > >: > > > >> > >> >> >>> For example, when trying to move a segment to the > > archive. > > > >> > >> >> > > > > >> > >> >> > We cannot do this, we will lost data. We can truncate > > > archived > > > >> > >> segment if > > > >> > >> >> > and only if it is not required for recovery. If last > > > checkpoint > > > >> > >> marker > > > >> > >> >> > points to segment > > > >> > >> >> > with lower index, we cannot delete any segment with > higher > > > >> index. > > > >> > >> So the > > > >> > >> >> > only moment where we can remove truncate segments is a > > > finish of > > > >> > >> >> checkpoint. > > > >> > >> >> > > > > >> > >> >> > пт, 6 нояб. 2020 г. в 09:46, ткаленко кирилл < > > > >> > tkalkir...@yandex.ru > > > >> > >> >: > > > >> > >> >> > > > > >> > >> >> >> Hello, everybody! > > > >> > >> >> >> > > > >> > >> >> >> As far as I know, WAL archive is used for PITP(GridGain > > > >> feature) > > > >> > >> and > > > >> > >> >> >> historical rebalancing. > > > >> > >> >> >> > > > >> > >> >> >> Facundo seems to have a problem with running out of > > > directory > > > >> > >> >> >> (/opt/work/walarchive) space. > > > >> > >> >> >> Currently, WAL archive is cleared at the end of > > checkpoint. > > > >> > >> Potentially > > > >> > >> >> >> long transaction may prevent checkpoint starting, > thereby > > > not > > > >> > >> cleaning > > > >> > >> >> WAL > > > >> > >> >> >> archive, which will lead to such an error. > > > >> > >> >> >> At the moment, I see such a WA to increase size of > > directory > > > >> > >> >> >> (/opt/work/walarchive) in k8s and avoid long > transactions > > or > > > >> > >> something > > > >> > >> >> like > > > >> > >> >> >> that that modifies data and runs for a long time. > > > >> > >> >> >> > > > >> > >> >> >> And it is best to fix the logic of working with WAL > > > archive. I > > > >> > >> think we > > > >> > >> >> >> should remove WAL archive cleanup from the end of the > > > >> checkpoint > > > >> > >> and > > > >> > >> >> do it > > > >> > >> >> >> on demand. For example, when trying to move a segment to > > the > > > >> > >> archive. > > > >> > >> >> >> > > > >> > >> >> >> 06.11.2020, 01:58, "Denis Magda" <dma...@apache.org>: > > > >> > >> >> >> > Folks, > > > >> > >> >> >> > > > > >> > >> >> >> > In my understanding, you need the archives only for > > > features > > > >> > >> such as > > > >> > >> >> >> PITR. > > > >> > >> >> >> > Considering, that the PITR functionality is not > provided > > > in > > > >> > >> Ignite > > > >> > >> >> why do > > > >> > >> >> >> > we have the archives enabled by default? > > > >> > >> >> >> > > > > >> > >> >> >> > How about having this feature disabled by default to > > > prevent > > > >> > the > > > >> > >> >> >> following > > > >> > >> >> >> > issues experienced by our users: > > > >> > >> >> >> > > > > >> > >> >> >> > > > >> > >> >> > > > >> > >> > > > >> > > > > >> > > > > > > http://apache-ignite-users.70518.x6.nabble.com/WAL-and-WAL-Archive-volume-size-recommendation-td34458.html > > > >> > >> >> >> > > > > >> > >> >> >> > - > > > >> > >> >> >> > Denis > > > >> > >> >> > > > > >> > >> >> > -- > > > >> > >> >> > Sincerely yours, Ivan Daschinskiy > > > >> > >> > > > > >> > >> > -- > > > >> > >> > Sincerely yours, Ivan Daschinskiy > > > >> > >> > > > >> > > > > > >> > > > > > >> > > -- > > > >> > > Sincerely yours, Ivan Daschinskiy > > > >> > > > > > >> > > > > >> > > > > >> > -- > > > >> > Sincerely yours, Ivan Daschinskiy > > > >> > > > > > > > > > -- > > > > Sincerely yours, Ivan Daschinskiy > > > > > > > > -- > <http://www.trimble.com/> > Raymond Wilson > Solution Architect, Civil Construction Software Systems (CCSS) > 11 Birmingham Drive | Christchurch, New Zealand > +64-21-2013317 Mobile > raymond_wil...@trimble.com > > < > https://worksos.trimble.com/?utm_source=Trimble&utm_medium=emailsign&utm_campaign=Launch > > >
