Background Jobs

This feature was introduced in NetBox v4.1.

NetBox plugins can defer certain operations by enqueuing background jobs, which are executed asynchronously by background workers. This is helpful for decoupling long-running processes from the user-facing request-response cycle.

For example, your plugin might need to fetch data from a remote system. Depending on the amount of data and the responsiveness of the remote server, this could take a few minutes. Deferring this task to a queued job ensures that it can be completed in the background, without interrupting the user. The data it fetches can be made available once the job has completed.

Job Runners

A background job implements a basic Job executor for all kinds of tasks. It has logic implemented to handle the management of the associated job object, rescheduling of periodic jobs in the given interval and error handling. Adding custom jobs is done by subclassing NetBox's JobRunner class.

JobRunner

Bases: ABC

Background Job helper class.

This class handles the execution of a background job. It is responsible for maintaining its state, reporting errors, and scheduling recurring jobs.

__init__(job)

Parameters:

Name	Type	Description	Default
job		The specific Job this JobRunner is executing.	required

run(*args, **kwargs) abstractmethod

Run the job.

A JobRunner class needs to implement this method to execute all commands of the job.

handle(job, *args, **kwargs) classmethod

Handle the execution of a Job.

This method is called by the Job Scheduler to handle the execution of all job commands. It will maintain the job's metadata and handle errors. For periodic jobs, a new job is automatically scheduled using its interval.

get_jobs(instance=None) classmethod

Get all jobs of this JobRunner related to a specific instance.

enqueue(*args, **kwargs) classmethod

Enqueue a new Job.

This method is a wrapper of Job.enqueue() using handle() as function callback. See its documentation for parameters.

enqueue_once(instance=None, schedule_at=None, interval=None, *args, **kwargs) classmethod

Enqueue a new Job once, i.e. skip duplicate jobs.

Like enqueue(), this method adds a new Job to the job queue. However, if there's already a job of this class scheduled for instance, the existing job will be updated if necessary. This ensures that a particular schedule is only set up once at any given time, i.e. multiple calls to this method are idempotent.

Note that this does not forbid running additional jobs with the enqueue() method, e.g. to schedule an immediate synchronization job in addition to a periodic synchronization schedule.

For additional parameters see enqueue().

Parameters:

Name	Type	Description	Default
instance		The NetBox object to which this job pertains (optional)	None
schedule_at		Schedule the job to be executed at the passed date and time	None
interval		Recurrence interval (in minutes)	None

Example

jobs.py

from netbox.jobs import JobRunner


class MyTestJob(JobRunner):
    class Meta:
        name = "My Test Job"

    def run(self, *args, **kwargs):
        obj = self.job.object
        # your logic goes here

You can schedule the background job from within your code (e.g. from a model's save() method or a view) by calling MyTestJob.enqueue(). This method passes through all arguments to Job.enqueue(). However, no name argument must be passed, as the background job name will be used instead.

Attributes

JobRunner attributes are defined under a class named Meta within the job. These are optional, but encouraged.

name

This is the human-friendly names of your background job. If omitted, the class name will be used.

Scheduled Jobs

As described above, jobs can be scheduled for immediate execution or at any later time using the enqueue() method. However, for management purposes, the enqueue_once() method allows a job to be scheduled exactly once avoiding duplicates. If a job is already scheduled for a particular instance, a second one won't be scheduled, respecting thread safety. An example use case would be to schedule a periodic task that is bound to an instance in general, but not to any event of that instance (such as updates). The parameters of the enqueue_once() method are identical to those of enqueue().

Tip

It is not forbidden to enqueue() additional jobs while an interval schedule is active. An example use of this would be to schedule a periodic daily synchronization, but also trigger additional synchronizations on demand when the user presses a button.

Example

jobs.py

from netbox.jobs import JobRunner


class MyHousekeepingJob(JobRunner):
    class Meta:
        name = "Housekeeping"

    def run(self, *args, **kwargs):
        # your logic goes here

__init__.py

from netbox.plugins import PluginConfig

class MyPluginConfig(PluginConfig):
    def ready(self):
        from .jobs import MyHousekeepingJob
        MyHousekeepingJob.setup(interval=60)

Task queues

Three task queues of differing priority are defined by default:

• High
• Default
• Low

Any tasks in the "high" queue are completed before the default queue is checked, and any tasks in the default queue are completed before those in the "low" queue.

Plugins can also add custom queues for their own needs by setting the queues attribute under the PluginConfig class. An example is included below:

class MyPluginConfig(PluginConfig):
    name = 'myplugin'
    ...
    queues = [
        'foo',
        'bar',
    ]

The PluginConfig above creates two custom queues with the following names my_plugin.foo and my_plugin.bar. (The plugin's name is prepended to each queue to avoid conflicts between plugins.)

Configuring the RQ worker process

By default, NetBox's RQ worker process only services the high, default, and low queues. Plugins which introduce custom queues should advise users to either reconfigure the default worker, or run a dedicated worker specifying the necessary queues. For example:

python manage.py rqworker my_plugin.foo my_plugin.bar