Django Authentication Timeout Error (H12) on Heroku with MongoDB Atlas

I have a question regarding an issue I’m facing. I built an authentication system in Django and connected it to a MongoDB Atlas database. The website is deployed on Heroku, but I’m encountering a timeout error on Heroku (Error H12). I’ve already checked the database connection, and it seems to be working. I also changed the timeout duration to 60 and 120 seconds, but neither resolved the issue. What could be causing this error?

ERROR MESSAGE :

heroku[router]: at=error code=H12 desc="Request timeout" method=GET path="/" host=XXXX (i changed my host name).herokuapp.com request_id=3f41-4c44-8740-a56e6191eb53 fwd="xx.xx.xx.xxx" dyno=web.1 connect=1ms service=30000ms status=503 bytes=0 protocol=https

I checked the MongoDB Atlas connection, and it appears to be working fine. I also adjusted the timeout settings, increasing the timeout to 60 and 120 seconds, hoping this would resolve the H12 error on Heroku. However, I was expecting the website to load properly without timing out, but the issue persists despite these changes.

The H12 error on Heroku indicates a “Request timeout” error, which happens when your app fails to return a response within 30 seconds. Even though you’ve adjusted the timeout in your app, Heroku enforces this 30-second limit on its dynos, and increasing the timeout on your end won’t extend this limit.

Here are some potential causes and solutions to investigate:

  1. Long-running database queries: Even if MongoDB Atlas is working, long queries or blocking operations could cause your Django app to hit the 30-second limit. You can:
  • Optimize database queries (use indexes, pagination, or asynchronous queries).
  • Log query times to identify any slow operations.
  1. Check for heavy processing in views: If a particular view is performing heavy computations or tasks that take time (e.g., file processing, external API calls), this could result in a timeout. Move these tasks to background workers using something like Celery or RQ with a task queue (e.g., Redis).
  2. Issue with gunicorn workers: Heroku uses a gunicorn web server by default, and by tweaking the number of workers, you can handle more requests concurrently. If you have fewer workers and each request is blocking, it could lead to timeouts. Try increasing the number of gunicorn workers. You can add this in your Procfile:
web: gunicorn backend.wsgi:application --workers 3 --timeout 60
  1. Heroku dyno scaling: If your app is handling a large number of requests, the timeout could occur due to load. Consider scaling up your dynos:
heroku ps:scale web=2

This will add an additional web dyno to handle requests.
5. Check for external API latency: If your app makes external API calls, they might be slowing down the response time. Use asynchronous calls or background workers to avoid holding up the main request cycle.
6. Heroku logs: Double-check your logs for any other errors that could hint at problems (e.g., database connection drops, memory limits, or other resource constraints).

By addressing potential bottlenecks in processing, database interactions, and external API calls, you can mitigate the H12 timeout errors.