rq-scheduler 0.3.0

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)

Periodic & Repeated Jobs

As of version 0.3, RQ Scheduler also supports creating periodic and repeated jobs. You can do this via the enqueue method. This is the syntax:

scheduler.enqueue(
    scheduled_time=datetime.now(), # Time for first execution
    func=func,                     # Function to be queued
    args=[arg1, arg2],             # Arguments passed into function when executed
    kwargs = {'foo': 'bar'},       # Keyword arguments passed into function when executed
    interval=60,                   # Time before the function is called again, in seconds
    repeat=10                      # Repeat this number of times (None means repeat forever)
)

Note that the syntax for passing arguments and keyword arguments into the queued function is slightly different than RQ’s. This is deliberatefor readability reasons and to prevent argument name clashes.

So for example if I want to check the number of retweets every minute:

scheduler.enqueue(
    datetime.now(),
    count_retweets,
    args=[tweet_id],
    interval=60
)

If we just want to count my retweets every minute for 10 minutes, we can use the repeat argument:

scheduler.enqueue(
    datetime.now(),
    count_retweets,
    args=[tweet_id],
    interval=60,
    repeat=10        # Only do this 10 times
)

If you prefer RQ’s original syntax, you can achieve the same thing using enqueue_periodic:

scheduler.enqueue_periodic(
    datetime.now(), # Time for first execution
    interval,       # Time to wait before job is queued again, in seconds
    repeat,         # Number of times function is to be repeated (None means repeat forever)
    func,           # Function to be queued
    *args,          # Arguments passed into function when executed
    **kwargs        # Keyword arguments passed into function when executed
)

# Using our retweet counting example:
scheduler.enqueue(
    datetime.now(),
    60,
    None,
    count_retweets,
    tweet_id,
)

Canceling a job

To cancel a job, simply do:

scheduler.cancel(job)

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