gitlab-foss/gems/gitlab-active-context/doc/how_it_works.md

How it works

Migrations

A cron worker runs every 5 minutes to apply outstanding migrations for the currently active connection.

If another connection is made active, the worker will apply that connection's outstanding migrations.

Async processing

A cron worker triggers a Sidekiq job for every queue in ActiveContext.raw_queues every minute. For each of the jobs, it fetches a set amount of references from the queue, processes them and removes them from the queue. The job will re-enqueue itself every second until there are no more references to process in the queue.

Async processing depends on the following configuration values:

1. indexing_enabled: processing exits early if this is false. Recommended to set to:

   config.indexing_enabled = Gitlab::CurrentSettings.elasticsearch_indexing? &&
     Search::ClusterHealthCheck::Elastic.healthy?
   

2. re_enqueue_indexing_workers: whether or not to re-enqueue workers until there are no more references to process. Increases indexing throughput when set to true. Recommended to set to:

   config.re_enqueue_indexing_workers = Gitlab::CurrentSettings.elasticsearch_requeue_workers?