Worker
A worker is a unit of processing, that dequeues jobs and executes them.
It is started with a list of queues to listen to, in a specific order.
It can be started with concurrency options (multiple processes and / or multiple greenlets). We call this whole group a single 'worker' even though it is able to dequeue multiple jobs in parallel.
Statuses
At any time, a worker is in one of these statuses:
init: General worker initializationwait: Waiting for new jobs from Redisspawn: Got some new jobs, greenlets are being spawnedfull: All the worker pool is busy executing jobsjoin: Waiting for current jobs to finish, no new one will be acceptedkill: Killing all current jobsstop: Worker is stopped, no jobs should remain