Display/cancel running indexing jobs in ES administration
Currently the ES administration doesn't provide any information about running indexing jobs, or a way to cancel them.
In our docs users are directed to either check the
elastic_indexer queue in Admin Area > Monitoring > Background Jobs > Queues, or use the
gitlab:elastic:index_projects_status Rake task to see a rough estimate of the indexing progress (this latter part would be moved to the administration with #38124).
The requirements for this aren't clear yet.
The backend could provide new API endpoints to check for running indexing jobs, and cancel them. This should also be available per-index if #38120 is already implemented.
The frontend could display this information somehow, and also use it to disable the "Reindex" / "Start indexing" buttons, or cancel running jobs before queueing new ones.