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
