Package: rq-scheduler
RQ SchedulerRQ Scheduleris a small package that
adds job scheduling capabilities toRQ,
aRedisbased Python queuing library.Support RQ SchedulerIf you findrq-scheduleruseful, please consider supporting its development viaTidelift.RequirementsRQInstallationYou can installRQ Schedulervia pip:pip install rq-schedulerOr you can download the latest stable package fromPyPI.UsageSchedule a job involves doing two different things:Putting a job in the schedulerRunning a scheduler that will move scheduled jobs into queues when the time comesScheduling a JobThere are two ways you can schedule a job. The first is using RQ Scheduler’senqueue_atfromredisimportRedisfromrqimportQueuefromrq_schedulerimportSchedulerfromdatetimeimportdatetimescheduler=Scheduler(connection=Redis())# Get a scheduler for the "default" queuescheduler=Scheduler('foo',connection=Redis())# Get a scheduler for the "foo" queue# You can also instantiate a Scheduler using an RQ Queuequeue=Queue('bar',connection=Redis())scheduler=Scheduler(queue=queue,connection=queue.connection)# 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)# Date time should be in UTC# Here's another example scheduling a job to run at a specific date and time (in UTC),# complete with args and kwargs.scheduler.enqueue_at(datetime(2020,1,1,3,4),func,foo,bar=baz)# You can choose the queue type where jobs will be enqueued by passing the name of the type to the scheduler# used to enqueuescheduler=Scheduler('foo',queue_class="rq.Queue")scheduler.enqueue_at(datetime(2020,1,1),func)# The job will be enqueued at the queue named "foo" using the queue type "rq.Queue"The second way is usingenqueue_in. Instead of taking adatetimeobject,
this method expects atimedeltaand 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 likefromdatetimeimporttimedelta# Schedule a job to run 10 minutes, 1 hour and 1 day laterscheduler.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)IMPORTANT: You should always use UTC datetime when working withRQ Scheduler.Periodic & Repeated JobsAs of version 0.3,RQ Scheduleralso supports creating periodic and repeated jobs.
You can do this via theschedulemethod. Note that this feature needsRQ>= 0.3.1.This is how you do itscheduler.schedule(scheduled_time=datetime.utcnow(),# Time for first execution, in UTC timezonefunc=func,# Function to be queuedargs=[arg1,arg2],# Arguments passed into function when executedkwargs={'foo':'bar'},# Keyword arguments passed into function when executedinterval=60,# Time before the function is called again, in secondsrepeat=10,# Repeat this number of times (None means repeat forever)meta={'foo':'bar'}# Arbitrary pickleable data on the job itself)IMPORTANT NOTE: If you set up a repeated job, you must make sure that you
either do not set aresult_ttlvalue or you set a value larger than the interval.
Otherwise, the entry with the job details will expire and the job will not get re-scheduled.Cron JobsAs of version 0.6.0,RQ Scheduleralso supports creating Cron Jobs, which you can use for
repeated jobs to run periodically at fixed times, dates or intervals, for more info checkhttps://en.wikipedia.org/wiki/Cron. You can do this via thecronmethod.This is how you do itscheduler.cron(cron_string,# A cron string (e.g. "0 0 * * 0")func=func,# Function to be queuedargs=[arg1,arg2],# Arguments passed into function when executedkwargs={'foo':'bar'},# Keyword arguments passed into function when executedrepeat=10,# Repeat this number of times (None means repeat forever)result_ttl=300# Specify how long (in seconds) successful jobs and their results are kept. Defaults to -1 (forever)ttl=200# Specifies the maximum queued time (in seconds) before it's discarded. Defaults to None (infinite TTL).queue_name=queue_name,# In which queue the job should be put inmeta={'foo':'bar'},# Arbitrary pickleable data on the job itselfuse_local_timezone=False# Interpret hours in the local timezone)Retrieving scheduled jobsSometimes you need to know which jobs have already been scheduled. You can get a
list of enqueued jobs with theget_jobsmethodlist_of_job_instances=scheduler.get_jobs()In it’s simplest form (as seen in the above example) this method returns a list
of all job instances that are currently scheduled for execution.Additionally the method takes two optional keyword argumentsuntilandwith_times. The first one specifies up to which point in time scheduled jobs
should be returned. It can be given as either a datetime / timedelta instance
or an integer denoting the number of seconds since epoch (1970-01-01 00:00:00).
The second argument is a boolean that determines whether the scheduled execution
time should be returned along with the job instances.Example# get all jobs until 2012-11-30 10:00:00list_of_job_instances=scheduler.get_jobs(until=datetime(2012,10,30,10))# get all jobs for the next hourlist_of_job_instances=scheduler.get_jobs(until=timedelta(hours=1))# get all jobs with execution timesjobs_and_times=scheduler.get_jobs(with_times=True)# returns a list of tuples:# [(<rq.job.Job object at 0x123456789>, datetime.datetime(2012, 11, 25, 12, 30)), ...]Checking if a job is scheduledYou can check whether a specific job instance or job id is scheduled for
execution using the familiar pythoninoperatorifjob_instanceinscheduler:# Do something# orifjob_idinscheduler:# Do somethingCanceling a jobTo cancel a job, simply pass aJobor a job id toscheduler.cancelscheduler.cancel(job)Note that this method returnsNonewhether the specified job was found or not.Running the schedulerRQ Schedulercomes with a scriptrqschedulerthat 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 connectionrqschedulerIf you want to use a different Redis server you could also dorqscheduler--hostlocalhost--port6379--db0The script accepts these arguments:-Hor--host: Redis server to connect to-por--port: port to connect to-dor--db: Redis db to use-Por--password: password to connect to Redis-bor--burst: runs in burst mode (enqueue scheduled jobs whose execution time is in the past and quit)-iINTERVALor--intervalINTERVAL: How often the scheduler checks for new jobs to add to the queue (in seconds, can be floating-point for more precision).-jor--job-class: specify custom job class for rq to use (python module.Class)-qor--queue-class: specify custom queue class for rq to use (python module.Class)The arguments pull default values from environment variables with the
same names but with a prefix ofRQ_REDIS_.Running the Scheduler as a Service on Ubuntusudo /etc/systemd/system/rqscheduler.service[Unit]Description=RQSchedulerAfter=network.target[Service]ExecStart=/home/<<User>>/.virtualenvs/<<YourVirtualEnv>>/bin/python \
    /home/<<User>>/.virtualenvs/<<YourVirtualEnv>>/lib/<<YourPythonVersion>>/site-packages/rq_scheduler/scripts/rqscheduler.py[Install]WantedBy=multi-user.targetYou will also want to add any command line parameters if your configuration is not localhost or not set in the environment variables.Start, check Status and Enable the servicesudosystemctlstartrqscheduler.servicesudosystemctlstatusrqscheduler.servicesudosystemctlenablerqscheduler.serviceRunning Multiple SchedulersMultiple instances of the rq-scheduler can be run simultaneously. It allows forReliability (no single point of failure)Failover (scheduler instances automatically retry to attain lock and schedule jobs)Running scheduler on multiple server instances to make deployment identical and easierMultiple schedulers can be run in any way you want. Typically you’ll only want to run one scheduler per server/instance.rqscheduler-i5# another shell/systemd service or ideally another serverrqscheduler-i5# different parameters can be provided to different schedulersrqscheduler-i10Practical example:scheduler_ais running onec2_instance_aIfscheduler_acrashes orec2_instance_agoes down, then our tasks won’t be scheduled at allInstead we can simply run 2 schedulers. Another scheduler calledscheduler_bcan be run onec2_instance_bNow bothscheduler_aandscheduler_bwill periodically check and schedule the jobsIf one fails, the other still worksYou can read more about multiple schedulers in#212and#195