By default, Sidekiq will retry 25 times with an exponential backoff.
This may result in jobs retrying for up to 21 days. Most Sidekiq
failures occur when attempting to connect to external services -
Project service hooks, web hooks, mailers, mirror updates, etc.
We should set a default retry of 3, and if that's not sufficient
individual workers can override this in the worker class.
The Sidekiq client API adds an entry to the Sidekiq "queues" list,
but mail_room and gitlab-shell use redis-rb directly to insert jobs
into Redis and thus do not make an extra "sadd" call to Redis
each time a job is inserted. To make it possible to monitor
these queues via the API, add an initialization step to
set up the list at startup.
Closesgitlab-com/infrastructure#682
Patricio Cano