PyCron — Python Based Job Scheduler

3 min readFeb 20, 2025

Building a Job Scheduler: A FastAPI-Powered Task Automation System

Task automation and job scheduling are fundamental components of modern software systems. In this article, I’ll guide you through building a robust Job Scheduler using FastAPI and APScheduler that handles dependent tasks through an intuitive web interface.

What We’re Building

Our Job Scheduler is a web-based application that allows you to:

Create and schedule jobs using cron syntax
Manage job dependencies
Monitor job execution through a dashboard
Execute jobs on-demand
Track comprehensive logs

Technical Architecture

The application is built using:

FastAPI: A modern, fast web framework for building APIs
APScheduler: Advanced Python Scheduler for job management
SQLAlchemy: SQL toolkit and ORM
Passlib + Bcrypt: For secure authentication
Jinja2: Template engine for the frontend

Source Code can be cloned from —

ankur-katiyar/PyCron: Job Scheduler is a robust web-based application developed using FastAPI and APScheduler

Project Structure

job-scheduler/
├── app/
│   ├── api.py
│   ├── models.py
│   └── main.py
├── k8s/
│   └── deployment.yaml
├── Dockerfile
├── requirements.txt
└── README.md

Getting Started

Prerequisites

Python 3.7+
Git
Basic understanding of cron syntax

Step 1: Clone the Repository

git clone https://github.com/yourusername/job-scheduler.git
cd job-scheduler

Successful repository clone

Step 2: Set Up Virtual Environment

For Windows:

python -m venv venv
venv\Scripts\activate

For Unix/MacOS:

python -m venv venv
source venv/bin/activate

Step 3: Install Dependencies

pip install -r requirements.txt

Contents of requirements.txt:

anyio==4.8.0
APScheduler==3.9.1
bcrypt==4.2.1
click==8.1.8
colorama==0.4.6
fastapi==0.95.1
greenlet==3.1.1
h11==0.14.0
idna==3.10
itsdangerous==2.2.0
Jinja2==3.1.2
MarkupSafe==3.0.2
passlib==1.7.4
pip==24.3.1
pydantic==1.10.21
python-multipart==0.0.20
pytz==2025.1
setuptools==75.8.0
six==1.17.0
sniffio==1.3.1
SQLAlchemy==1.4.48
starlette==0.26.1
typing_extensions==4.12.2
tzdata==2025.1
tzlocal==5.3
uvicorn==0.22.0

Step 4: Start the Application

uvicorn app.api:app --host 0.0.0.0 --port 8000 --reload

Core Features Deep Dive

1. Job Creation

Jobs are defined with:

A unique name
Cron schedule
Command to execute
Optional dependencies

Sample job configuration:

{
    "name": "data_processing",
    "schedule": "*/15 * * * *",  # Every 15 minutes
    "command": "python process_data.py",
    "dependencies": [1, 2]  # Must wait for jobs 1 and 2
}

2. Kubernetes Deployment

For production environments, we provide Kubernetes manifests in k8s/deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: job-scheduler
spec:
  replicas: 1
  selector:
    matchLabels:
      app: job-scheduler
  template:
    spec:
      containers:
      - name: job-scheduler
        image: job-scheduler:latest
        ports:
        - containerPort: 8000

Docker Support

The application includes a Dockerfile for containerization:

FROM python:3.12-slim

WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txtCOPY app/ .CMD ["uvicorn", "api:app", "--host", "0.0.0.0", "--port", "8000"]

Security Features

The application implements several security measures:

1. Password Hashing

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

2. Session Management

app.add_middleware(SessionMiddleware, 
    secret_key=os.environ.get("SECRET_KEY"))

Contributing

We welcome contributions! Visit our GitHub repository:

github.com/yourusername/job-scheduler

Resources

Job Scheduler running with multiple scheduled tasks

This project is open source and available under the MIT license. Feel free to use it, modify it, and contribute back to the community!

Tags: Python, FastAPI, DevOps, Automation, Programming, WebDevelopment, OpenSource