GitLab Enterprise Edition allows one to start an extra set of Sidekiq processes besides the default one. These processes can be used to consume a dedicated set of queues. This can be used to ensure certain queues always have dedicated workers, no matter the amount of jobs that need to be processed.
Starting extra Sidekiq processes can be done using the command
bin/sidekiq-cluster. This command takes arguments using the following syntax:
sidekiq-cluster [QUEUE,QUEUE,...] [QUEUE, ...]
Each separate argument denotes a group of queues that have to be processed by a Sidekiq process. Multiple queues can be processed by the same process by separating them with a comma instead of a space.
For example, say you want to start 2 extra processes: one to process the "process_commit" queue, and one to process the "post_receive" queue. This can be done as follows:
sidekiq-cluster process_commit post_receive
If you instead want to start one process processing both queues you'd use the following syntax:
If you want to have one Sidekiq process process the "process_commit" and "post_receive" queues, and one process to process the "gitlab_shell" queue, you'd use the following:
sidekiq-cluster process_commit,post_receive gitlab_shell
Each process started using
sidekiq-cluster starts with a number of threads that equals the number of queues, plus one spare thread. For example, a process that processes "process_commit" and "post_receive" will use 3 threads in total.
sidekiq-cluster command will not terminate once it has started the desired amount of Sidekiq processes. Instead the process will continue running and forward any signals to the child processes. This makes it easy to stop all Sidekiq processes as you simply send a signal to the
sidekiq-cluster process, instead of having to send it to the individual processes.
sidekiq-cluster process crashes or is SIGKILL'd the child processes will terminate themselves after a few seconds. This ensures you don't end up with zombie Sidekiq processes.
All of this makes monitoring the processes fairly easy. Simply hook up
sidekiq-cluster to your supervisor of choice (e.g. runit) and you're good to go.
If a child process died the
sidekiq-cluster command will signal all remaining process to terminate, then terminate itself. This removes the need for
sidekiq-cluster to re-implement complex process monitoring/restarting code. Instead you should make sure your supervisor restarts the
sidekiq-cluster process whenever necessary.
sidekiq-cluster command can store its PID in a file. By default no PID file is written, but this can be changed by passing the
--pidfile option to
sidekiq-cluster. For example:
sidekiq-cluster --pidfile /var/run/gitlab/sidekiq_cluster.pid process_commit
Keep in mind that the PID file will contain the PID of the
sidekiq-cluster command, and not the PID(s) of the started Sidekiq processes.
The Rails environment can be set by passing the
--environment flag to the
sidekiq-cluster command, or by setting
RAILS_ENV to a non-empty value. The default value is "development".