gitlab-org--gitlab-foss/doc/development/sidekiq_style_guide.md
Yorick Peterse 97731760d7
Re-organize queues to use for Sidekiq
Dumping too many jobs in the same queue (e.g. the "default" queue) is a
dangerous setup. Jobs that take a long time to process can effectively
block any other work from being performed given there are enough of
these jobs.

Furthermore it becomes harder to monitor the jobs as a single queue
could contain jobs for different workers. In such a setup the only
reliable way of getting counts per job is to iterate over all jobs in a
queue, which is a rather time consuming process.

By using separate queues for various workers we have better control over
throughput, we can add weight to queues, and we can monitor queues
better. Some workers still use the same queue whenever their work is
related. For example, the various CI pipeline workers use the same
"pipeline" queue.

This commit includes a Rails migration that moves Sidekiq jobs from the
old queues to the new ones. This migration also takes care of doing the
inverse if ever needed. This does require downtime as otherwise new jobs
could be scheduled in the old queues after this migration completes.

This commit also includes an RSpec test that blacklists the use of the
"default" queue and ensures cron workers use the "cronjob" queue.

Fixes gitlab-org/gitlab-ce#23370
2016-10-21 18:17:07 +02:00

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Markdown

# Sidekiq Style Guide
This document outlines various guidelines that should be followed when adding or
modifying Sidekiq workers.
## Default Queue
Use of the "default" queue is not allowed. Every worker should use a queue that
matches the worker's purpose the closest. For example, workers that are to be
executed periodically should use the "cronjob" queue.
A list of all available queues can be found in `config/sidekiq_queues.yml`.
## Dedicated Queues
Most workers should use their own queue. To ease this process a worker can
include the `DedicatedSidekiqQueue` concern as follows:
```ruby
class ProcessSomethingWorker
include Sidekiq::Worker
include DedicatedSidekiqQueue
end
```
This will set the queue name based on the class' name, minus the `Worker`
suffix. In the above example this would lead to the queue being
`process_something`.
In some cases multiple workers do use the same queue. For example, the various
workers for updating CI pipelines all use the `pipeline` queue. Adding workers
to existing queues should be done with care, as adding more workers can lead to
slow jobs blocking work (even for different jobs) on the shared queue.
## Tests
Each Sidekiq worker must be tested using RSpec, just like any other class. These
tests should be placed in `spec/workers`.