vivek807 opened a new pull request, #19603: URL: https://github.com/apache/druid/pull/19603
Fixes #19602. ### Description `forceOrWaitOngoingDatabasePoll` in `SqlSegmentsMetadataManager` checks whether a concurrent `OnDemandDatabasePoll` that completed while the calling thread waited for the write lock makes a new poll unnecessary. This check was always false due to a clock mismatch, causing an extra database poll on every contended call. #### Fixed invalid clock comparison in `forceOrWaitOngoingDatabasePoll` `OnDemandDatabasePoll.initiationTimeNanos` is assigned via `System.nanoTime()`, which is a monotonic clock with an arbitrary JVM-internal reference point. The comparison value was constructed as: ```java long checkStartTimeNanos = TimeUnit.MILLISECONDS.toNanos(checkStartTime); // checkStartTime = System.currentTimeMillis() ``` System.currentTimeMillis() returns milliseconds since the Unix epoch (~1.7 × 10¹² ms). Converting to nanoseconds yields ~1.7 × 10²¹ ns, which is orders of magnitude larger than any System.nanoTime() value. The condition `initiationTimeNanos > checkStartTimeNanos` was therefore always false, so an in-progress on-demand poll was never recognised as sufficient. <!-- Replace XXXX with the id of the issue fixed in this PR. Remove this section if there is no corresponding issue. Don't reference the issue in the title of this pull-request. --> <!-- If you are a committer, follow the PR action item checklist for committers: https://github.com/apache/druid/blob/master/dev/committer-instructions.md#pr-and-issue-action-item-checklist-for-committers. --> This PR has: - [x] been self-reviewed. - [ ] using the [concurrency checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md) (Remove this item if the PR doesn't have any relation to concurrency.) - [ ] added documentation for new or modified features or behaviors. - [ ] a release note entry in the PR description. - [ ] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links. - [ ] added or updated version, license, or notice information in [licenses.yaml](https://github.com/apache/druid/blob/master/dev/license.md) - [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader. - [ ] added unit tests or modified existing tests to cover new code paths, ensuring the threshold for [code coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md) is met. - [ ] added integration tests. - [ ] been tested in a test Druid cluster. -- 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]
