Implementation of Django APScheduler with PostgreSQL

Introduction:

APScheduler is a Python library that allows you to schedule jobs for future execution; you can schedule multiple jobs and maintain them independently. By using this, you can schedule different types of jobs are given:

  • Cron-based scheduling
  • Interval-based scheduling.
  • Date (on a specific date and time) based scheduling.

Preface:

You are reading this, so I am assuming that you are already familiar with Django and developing web projects. Here, I will talk about a package from which the schedule will become easier to implement. If you want to read more about APScheduler, you can read it on the official website.

Need of this blog:

While using APScheduler with Django, you will face a problem when the server restarts all the scheduled jobs lost. APScheduler stores all the jobs on a temporary basis; all the jobs will be lost when the server restarts. For this, we have to manage Jobs from a database, so when the server restarts, it will get all lost jobs from the database

Implementation:

Now, I will show you how you can use PostgreSQL with Django. The reason for using a database with APScheduler is simple: when the Django server restarts, your scheduled jobs will be lost due to being stored in temporary memory.

You all need to do is follow these steps:

1. Create a Django project, and don’t forget to activate the virtual environment and install Django. I will name the project “scheduler

2. Create a Django app named “tasks” and your project structure will look like this.

                                                                                                                                                                                                                                                                                                                                                                                                

3. Install this library using your pip command in your command prompt

 4. Add this given app into your installed apps in the settings.py file.

INSTALLED_APPS = [
 # .........
    "tasks",
    "rest_apscheduler",
]

5. Update DATABASE connections in settings.py. Plus point of this package, you can use a database of your choice like MySQL, SQLite etc.

DATABASES = {
   'default': {
       'ENGINE': 'django.db.backends.postgresql',
       'NAME': os.getenv("DB_NAME"),
       'USER': os.getenv("DB_USER"),
       'PASSWORD': os.getenv("DB_PASSWORD"),
       'HOST': os.getenv("DB_HOST_SERVER"),
       'PORT': os.getenv("DB_PORT"),
   }
}

6. We are one step ahead, just run this command to migrate models.

python manage.py migrate.

All set, Now you need to import this Scheduler in your views.py file and ready to schedule jobs.

from rest_apscheduler.scheduler import Scheduler


def job_task():
    print("your task has been executed successfully..")

class SchedulerJobAPIView(CreateAPIView):
    """
    class for scheduling a new job.
"""
    authentication_classes = ()
    permission_classes = ()
    serializer_class = JobSerializer

    def post(self, request, *args, **kwargs):
        job_serializer = self.get_serializer(data=request.data)

        if job_serializer.is_valid(raise_exception=True):
            schedule_date = job_serializer.validated_data("schedule_date")
            Scheduler.add_job(
                job_task,
                trigger=DateTrigger(run_date=schedule_date),
                replace_existing=True
            )

        Return Response(status=status.HTTP_200_OK, data={"result": "Success."})

Now you can create as many jobs as you want and it will never lose data until something happens to DB.

In DB you can now manage which executed successfully and which throws errors in the table “rest_apscheduler_djangojobexecution”.

coma

Conclusion

Here we discussed how we can create jobs of different types. I am also sharing a GitHub repo for this package. You can also go through the official website of APScheduler and read more about working.

https://github.com/Ronakjain515/django-rest-apscheduler

https://apscheduler.readthedocs.io/en/stable/userguide.html

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