I noticed an entry in the Ignite 2.9.1 changelog: - Improved checkpoint concurrent behaviour
I am having trouble finding the relevant Jira ticket for this in the 2.9.1 Jira area at https://issues.apache.org/jira/browse/IGNITE-13876?jql=project%20%3D%20IGNITE%20AND%20fixVersion%20%3D%202.9.1%20and%20status%20%3D%20Resolved Perhaps this change may improve the checkpointing issue we are seeing? Raymond. On Tue, Dec 29, 2020 at 8:35 PM Raymond Wilson <[email protected]> wrote: > Hi Zhenya, > > 1. We currently use AWS EFS for primary storage, with provisioned IOPS to > provide sufficient IO. Our Ignite cluster currently tops out at ~10% usage > (with at least 5 nodes writing to it, including WAL and WAL archive), so we > are not saturating the EFS interface. We use the default page size > (experiments with larger page sizes showed instability when checkpointing > due to free page starvation, so we reverted to the default size). > > 2. Thanks for the detail, we will look for that in thread dumps when we > can create them. > > 3. We are using the default CP buffer size, which is max(256Mb, > DataRagionSize / 4) according to the Ignite documentation, so this should > have more than enough checkpoint buffer space to cope with writes. As > additional information, the cache which is displaying very slow writes is > in a data region with relatively slow write traffic. There is a primary > (default) data region with large write traffic, and the vast majority of > pages being written in a checkpoint will be for that default data region. > > 4. Yes, this is very surprising. Anecdotally from our logs it appears > write traffic into the low write traffic cache is blocked during > checkpoints. > > Thanks, > Raymond. > > > > On Tue, Dec 29, 2020 at 7:31 PM Zhenya Stanilovsky <[email protected]> > wrote: > >> >> 1. Additionally to Ilya reply you can check vendors page for >> additional info, all in this page are applicable for ignite too [1]. >> Increasing threads number leads to concurrent io usage, thus if your have >> something like nvme — it`s up to you but in case of sas possibly better >> would be to reduce this param. >> 2. Log will shows you something like : >> >> Parking thread=%Thread name% for timeout(ms)= %time% >> >> and appropriate : >> >> Unparking thread= >> >> 3. No additional looging with cp buffer usage are provided. cp buffer >> need to be more than 10% of overall persistent DataRegions size. >> 4. 90 seconds or longer — Seems like problems in io or system >> tuning, it`s very bad score i hope. >> >> [1] >> https://www.gridgain.com/docs/latest/perf-troubleshooting-guide/persistence-tuning >> >> >> >> >> >> Hi, >> >> We have been investigating some issues which appear to be related to >> checkpointing. We currently use the IA 2.8.1 with the C# client. >> >> I have been trying to gain clarity on how certain aspects of the Ignite >> configuration relate to the checkpointing process: >> >> 1. Number of check pointing threads. This defaults to 4, but I don't >> understand how it applies to the checkpointing process. Are more threads >> generally better (eg: because it makes the disk IO parallel across the >> threads), or does it only have a positive effect if you have many data >> storage regions? Or something else? If this could be clarified in the >> documentation (or a pointer to it which Google has not yet found), that >> would be good. >> >> 2. Checkpoint frequency. This is defaulted to 180 seconds. I was thinking >> that reducing this time would result in smaller less disruptive check >> points. Setting it to 60 seconds seems pretty safe, but is there a >> practical lower limit that should be used for use cases with new data >> constantly being added, eg: 5 seconds, 10 seconds? >> >> 3. Write exclusivity constraints during checkpointing. I understand that >> while a checkpoint is occurring ongoing writes will be supported into the >> caches being check pointed, and if those are writes to existing pages then >> those will be duplicated into the checkpoint buffer. If this buffer becomes >> full or stressed then Ignite will throttle, and perhaps block, writes until >> the checkpoint is complete. If this is the case then Ignite will emit >> logging (warning or informational?) that writes are being throttled. >> >> We have cases where simple puts to caches (a few requests per second) are >> taking up to 90 seconds to execute when there is an active check point >> occurring, where the check point has been triggered by the checkpoint >> timer. When a checkpoint is not occurring the time to do this is usually in >> the milliseconds. The checkpoints themselves can take 90 seconds or longer, >> and are updating up to 30,000-40,000 pages, across a pair of data storage >> regions, one with 4Gb in-memory space allocated (which should be 1,000,000 >> pages at the standard 4kb page size), and one small region with 128Mb. >> There is no 'throttling' logging being emitted that we can tell, so the >> checkpoint buffer (which should be 1Gb for the first data region and 256 Mb >> for the second smaller region in this case) does not look like it can fill >> up during the checkpoint. >> >> It seems like the checkpoint is affecting the put operations, but I don't >> understand why that may be given the documented checkpointing process, and >> the checkpoint itself (at least via Informational logging) is not >> advertising any restrictions. >> >> Thanks, >> Raymond. >> >> -- >> <http://www.trimble.com/> >> Raymond Wilson >> Solution Architect, Civil Construction Software Systems (CCSS) >> >> >> >> >> >> >> > > > -- > <http://www.trimble.com/> > Raymond Wilson > Solution Architect, Civil Construction Software Systems (CCSS) > 11 Birmingham Drive | Christchurch, New Zealand > +64-21-2013317 Mobile > [email protected] > > > <https://worksos.trimble.com/?utm_source=Trimble&utm_medium=emailsign&utm_campaign=Launch> > -- <http://www.trimble.com/> Raymond Wilson Solution Architect, Civil Construction Software Systems (CCSS) 11 Birmingham Drive | Christchurch, New Zealand +64-21-2013317 Mobile [email protected] <https://worksos.trimble.com/?utm_source=Trimble&utm_medium=emailsign&utm_campaign=Launch>
