Discuss this with Kirill verbally. Kirill showed me that having the min threshold doesn't quite work. It doesn't work because we no longer know how much WAL we should remove if we reach getMaxWalArchiveSize.
For example, say we have minWalArchiveTimespan=2 hours and maxWalArchiveSize=2GB. Say, under normal load on stable topology 2 hours of WAL use 1 GB of space. Now, say we're doing historical rebalance and reserve the WAL archive. The WAL archive starts growing and soon it occupies 2 GB. Now what? We're supposed to give up WAL reservations and start agressively removing WAL archive. But it is not clear when can we stop removing WAL archive - since last 2 hours of WAL are larger than our maxWalArchiveSize there is no meaningful point the system can use as a "minimum" WAL size. I understand the description above is a bit messy but I believe that whoever is interested in this will understand it after drawing this on paper. I'm giving up on my latest suggestion about time-based minimum. Let's keep it simple. I suggest the minWalArchiveSize and maxWalArchvieSize properties as the solution, with the behavior as initially described by Kirill. Stan > On 7 May 2021, at 15:09, ткаленко кирилл <tkalkir...@yandex.ru> wrote: > > Stas hello! > > I didn't quite get your last idea. > What will we do if we reach getMaxWalArchiveSize? Shall we not delete the > segment until minWalArchiveTimespan? > > 06.05.2021, 20:00, "Stanislav Lukyanov" <stanlukya...@gmail.com>: >> An interesting suggestion I heard today. >> >> The minWalArchiveSize property might actually be minWalArchiveTimespan - >> i.e. be a number of seconds instead of a number of bytes! >> >> I think this makes perfect sense from the user point of view. >> "I want to have WAL archive for at least N hours but I have a limit of M >> gigabytes to store it". >> >> Do we have checkpoint timestamp stored anywhere? (cp start markers?) >> Perhaps we can actually implement this? >> >> Thanks, >> Stan >> >>> On 6 May 2021, at 14:13, Stanislav Lukyanov <stanlukya...@gmail.com> wrote: >>> >>> +1 to cancel WAL reservation on reaching getMaxWalArchiveSize >>> +1 to add a public property to replace >>> IGNITE_THRESHOLD_WAL_ARCHIVE_SIZE_PERCENTAGE >>> >>> I don't like the name getWalArchiveSize - I think it's a bit confusing (is >>> it the current size? the minimal size? the target size?) >>> I suggest to name the property geMintWalArchiveSize. I think that this is >>> exactly what it is - the minimal size of the archive that we want to have. >>> The archive size at all times should be between min and max. >>> If archive size is less than min or more than max then the system >>> functionality can degrade (e.g. historical rebalance may not work as >>> expected). >>> I think these rules are intuitively understood from the "min" and "max" >>> names. >>> >>> Ilya's suggestion about throttling is great although I'd do this in a >>> different ticket. >>> >>> Thanks, >>> Stan >>> >>>> On 5 May 2021, at 19:25, Maxim Muzafarov <mmu...@apache.org> wrote: >>>> >>>> Hello, Kirill >>>> >>>> +1 for this change, however, there are too many configuration settings >>>> that exist for the user to configure Ignite cluster. It is better to >>>> keep the options that we already have and fix the behaviour of the >>>> rebalance process as you suggested. >>>> >>>> On Tue, 4 May 2021 at 19:01, ткаленко кирилл <tkalkir...@yandex.ru> wrote: >>>>> Hi Ilya! >>>>> >>>>> Then we can greatly reduce the user load on the cluster until the >>>>> rebalance is over. Which can be critical for the user. >>>>> >>>>> 04.05.2021, 18:43, "Ilya Kasnacheev" <ilya.kasnach...@gmail.com>: >>>>>> Hello! >>>>>> >>>>>> Maybe we can have a mechanic here similar (or equal) to checkpoint based >>>>>> write throttling? >>>>>> >>>>>> So we will be throttling for both checkpoint page buffer and WAL limit. >>>>>> >>>>>> Regards, >>>>>> -- >>>>>> Ilya Kasnacheev >>>>>> >>>>>> вт, 4 мая 2021 г. в 11:29, ткаленко кирилл <tkalkir...@yandex.ru>: >>>>>> >>>>>>> Hello everybody! >>>>>>> >>>>>>> At the moment, if there are partitions for the rebalance for which the >>>>>>> historical rebalance will be used, then we reserve segments in the WAL >>>>>>> archive (we do not allow cleaning the WAL archive) until the rebalance >>>>>>> for >>>>>>> all cache groups is over. >>>>>>> >>>>>>> If a cluster is under load during the rebalance, WAL archive size may >>>>>>> significantly exceed limits set in >>>>>>> DataStorageConfiguration#getMaxWalArchiveSize until the process is >>>>>>> complete. This may lead to user issues and nodes may crash with the "No >>>>>>> space left on device" error. >>>>>>> >>>>>>> We have a system property IGNITE_THRESHOLD_WAL_ARCHIVE_SIZE_PERCENTAGE >>>>>>> by >>>>>>> default 0.5, which sets the threshold (multiplied by >>>>>>> getMaxWalArchiveSize) >>>>>>> from which and up to which the WAL archive will be cleared, i.e. sets >>>>>>> the >>>>>>> size of the WAL archive that will always be on the node. I propose to >>>>>>> replace this system property with the >>>>>>> DataStorageConfiguration#getWalArchiveSize in bytes, the default is >>>>>>> (getMaxWalArchiveSize * 0.5) as it is now. >>>>>>> >>>>>>> Main proposal: >>>>>>> When theDataStorageConfiguration#getMaxWalArchiveSize is reached, >>>>>>> cancel >>>>>>> and do not give the reservation of the WAL segments until we reach >>>>>>> DataStorageConfiguration#getWalArchiveSize. In this case, if there is >>>>>>> no >>>>>>> segment for historical rebalance, we will automatically switch to full >>>>>>> rebalance.
