clintropolis opened a new pull request #9563: add lane enforcement for joinish queries URL: https://github.com/apache/druid/pull/9563 ### Description This PR partially squares up the joins work of #9503, #9533, and #9545 with the query laning added in #9407, by extending lane enforcement to queries that run with the `LocalQuerySegmentWalker` of `ClientQuerySegmentWalker`, fixing a bug that queries that _only_ use the `LocalQuerySegmentWalker` are not counted at all. This PR puts things into an interim state so that these queries can fall under lane enforcement, but it has a flaw that it will sequentially acquire and release lanes for each time the `ClientQuerySegmentWalker` invokes either its local or cluster walker to run a part of a query rather than acquiring all necessary lanes up front and holding through the duration of the query. This is not really an ideal state, since it opens the possibility to fail midway through if a query loses a lane to another query, but it is better than not counting them, and so worth doing for the short term I think. Ideally, we could bring up the call to `QueryScheduler.run` into `ClientQuerySegmentWalker` or even the http resources, but this isn't currently possible without a fairly heavy refactor of how the broker runs queries. This is due to how they are transformed on the way down, where `QueryScheduler.prioritizeAndLaneQuery` happens on in the deepest part of the cluster and local walkers runners right before they call `QueryScheduler.run` because that is when the segments participating in the query are available. I'm not quite sure what this will look like, yet. <hr> This PR has: - [x] been self-reviewed. - [x] 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. - [x] added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links. - [ ] added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader. - [x] added unit tests or modified existing tests to cover new code paths. - [ ] added integration tests. - [ ] been tested in a test Druid cluster. <!-- Check the items by putting "x" in the brackets for the done things. Not all of these items apply to every PR. Remove the items which are not done or not relevant to the PR. None of the items from the checklist above are strictly necessary, but it would be very helpful if you at least self-review the PR. --> <hr> ##### Key changed/added classes in this PR * `LocalQuerySegmentWalker `
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