FrankChen021 opened a new pull request, #18136: URL: https://github.com/apache/druid/pull/18136
### Description Use Case If a Druid cluster is physically deployed in two AZs, we want the queries to be executed within one AZ as possible. This means queries from brokers to historicals should be executed on the nodes in the same AZ as possible. See the diagram as below:  This PR adds a new tier selector at broker side so that we can configure brokers to select historicals based on tier name(in this use case, the tier name can configured as the AZ name). And if there're no servers in given tier(typically this is the case when historicals in one AZ are under maintance), brokers can still select historicals in another tier(AZ). And to use this strategy, users also needs to make changes to their load rules to ensure segments are loaded in two tier(AZ) 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.) - [x] 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. - [x] 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]
