RQ Scheduler

RQ Scheduler is a small package that adds job scheduling capabilities to RQ, a Redis based Python queuing library.

Requirements

Installation

You can install RQ Scheduler via pip:

pip install rq-scheduler

Usage

Schedule a job involves doing two different things: # Putting a job in the scheduler # Running a scheduler that will move scheduled jobs into queues when the time comes

Scheduling a Job

There are two ways you can schedule a job. The first is using RQ Scheduler's enqueue_at:

from rq import use_connection
from rq_scheduler import Scheduler
from datetime import datetime

use_connection() # Use RQ's default Redis connection
scheduler = Scheduler() # Get a scheduler for the "default" queue

# Puts a job into the scheduler. The API is similar to RQ except that it
# takes a datetime object as first argument. So for example to schedule a
# job to run on Jan 1st 2020 we do:
scheduler.enqueue_at(datetime(2020, 1, 1), func)

# Here's another example scheduling a job to run at a specific date and time,
# complete with args and kwargs
scheduler.enqueue_at(datetime(2020, 1, 1, 3, 4), func, foo, bar=baz)

The second way is using enqueue_in. Instead of taking a datetime object, this method expects a timedelta and schedules the job to run at X seconds/minutes/hours/days/weeks later. For example, if we want to monitor how popular a tweet is a few times during the course of the day, we could do something like:

from datetime import timedelta

# Schedule a job to run 10 minutes, 1 hour and 1 day later
scheduler.enqueue_in(timedelta(minutes=10), count_retweets, tweet_id)
scheduler.enqueue_in(timedelta(hours=1), count_retweets, tweet_id)
scheduler.enqueue_in(timedelta(days=1), count_retweets, tweet_id)

You can also explicitly pass in connection to use a different Redis server:

from redis import Redis
from rq_scheduler import Scheduler
from datetime import datetime

scheduler = Scheduler('default', connection=Redis('192.168.1.3', port=123)) 
scheduler.enqueue_at(datetime(2020, 01, 01, 1, 1), func)

Running the scheduler

RQ Scheduler comes with a script rqscheduler that runs a scheduler process that polls Redis once every minute and move scheduled jobs to the relevant queues when they need to be executed:

# This runs a scheduler process using the default Redis connection
rqscheduler

If you want to use a different Redis server you could also do:

rqscheduler --host localhost --port 6379 --db 0

The script accepts these arguments:

-H or --host: Redis server to connect to
-p or --port: port to connect to
-d or --db: Redis db to use
-P or --password: password to connect to Redis