richardstartin opened a new pull request #7535: URL: https://github.com/apache/pinot/pull/7535
… in undersized environments ## Description Having discussed the problem with @suddendust and @subintp, the memory mapping error observed in #7476 appears to be correlated with very high disk usage, rather than high tmpfs usage as I initially suspected. They are using inverted and range indexes. The assumption behind `BitmapInvertedIndexWriter` is that there is a lot of disk space available, and that it's ok to overmap and truncate in order to avoid syscall overhead, but this results in high disk usage. Allocating file space for the serialised inverted indexes as it is needed feels like a good usability tradeoff. The strategy builds on some knowledge about how the bitmaps get serialised: a single bitmap never needs more than 256MB, so we never map more than 256MB at a time. Bitmaps should be fairly sparse most of the time, so we guess that we need `numBitmaps * 64KB` but if this estimate proves to be too small, the pessimistic 256MB is used for the next section. An alternative approach I considered is to just build the bitmaps all at once on heap, compute their sizes, then map the space needed once, which would be optimal in terms of disk usage and syscalls, but may lead to a little extra medium lifespan garbage. ## Upgrade Notes Does this PR prevent a zero down-time upgrade? (Assume upgrade order: Controller, Broker, Server, Minion) * [ ] Yes (Please label as **<code>backward-incompat</code>**, and complete the section below on Release Notes) Does this PR fix a zero-downtime upgrade introduced earlier? * [ ] Yes (Please label this as **<code>backward-incompat</code>**, and complete the section below on Release Notes) Does this PR otherwise need attention when creating release notes? Things to consider: - New configuration options - Deprecation of configurations - Signature changes to public methods/interfaces - New plugins added or old plugins removed * [ ] Yes (Please label this PR as **<code>release-notes</code>** and complete the section on Release Notes) ## Release Notes <!-- If you have tagged this as either backward-incompat or release-notes, you MUST add text here that you would like to see appear in release notes of the next release. --> <!-- If you have a series of commits adding or enabling a feature, then add this section only in final commit that marks the feature completed. Refer to earlier release notes to see examples of text. --> ## Documentation <!-- If you have introduced a new feature or configuration, please add it to the documentation as well. See https://docs.pinot.apache.org/developers/developers-and-contributors/update-document --> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
