<!-- Title suggestion: [Feature flag] Enable description of feature --> ## What Enable the `:rebalance_issues` feature flag. ## Owners - Team: Create / Source Code - Most appropriate slack channel to reach out to: `#g_create_source_code` - Best individual to reach out to: @acroitor ## Expectations ### What are we expecting to happen? Problematic issue sets (ones that show large numbers of timeouts and `NoSpaceLeft` exceptions) should begin rebalancing, and the incidence of these errors should decline. ### What might happen if this goes wrong? This may consume a large number of resources in the worker, since this can be a long running worker, which may itself timeout. We should watch for spikes in queue processing time. ### What can we monitor to detect problems with this? We should watch sentry for `NoSpaceLeft` and any error in the `IssueRebalancingWorker`. We should watch kibana to observe queue sizes: - [NoSpaceLeft](https://sentry.gitlab.net/gitlab/gitlabcom/?query=is%3Aunresolved+NoSpaceLeft) - [Issues::RelativePositionRebalancingService](https://sentry.gitlab.net/gitlab/gitlabcom/?query=is%3Aunresolved+RelativePositionRebalancingService) ## Roll Out Steps - [x] Enable on staging - [x] Test on staging - [x] Ensure that documentation has been updated - [x] Enable on GitLab.com for individual groups/projects listed above and verify behaviour - [x] Coordinate a time to enable the flag with `#production` and `#g_delivery` on slack. - [x] Announce on the issue an estimated time this will be enabled on GitLab.com - [x] Enable on GitLab.com by running chatops command in `#production` - [ ] Cross post chatops slack command to `#support_gitlab-com` ([more guidance when this is necessary in the dev docs](https://docs.gitlab.com/ee/development/feature_flags/controls.html#where-to-run-commands)) and in your team channel - [ ] Announce on the issue that the flag has been enabled - [ ] Remove feature flag and add changelog entry - [ ] After the flag removal is deployed, [clean up the feature flag](https://docs.gitlab.com/ee/development/feature_flags/controls.html#cleaning-up) by running chatops command in `#production` channelb