`bench start` crash (not working) in Frappe

Frappe Framework Bug
,
1

bench start crash (not working) in Frappe

Solutions for two common issues in Frappe development while trying to start the bench:

  • Port conflicts that prevent bench start from working.

  • Crashes caused by old or corrupted cache content.

i don’t know why but it always happen because of redis issue (either port or cache)

The Solution In Short:


sudo lsof -i :11000

sudo kill <PID1> <PID2> <PID3> .....

sudo lsof -i :13000

sudo kill <PID1> <PID2> <PID3> .....

bench --site your-site-name clear-cache

bench --site your-site-name clear-website-cache

bench start

Explaination:

Part 1: Fixing Port Conflicts in Frappe

When running bench start, you might see errors like:


TCP listening socket on 127.0.0.1:11000 is already in use.

TCP listening socket on 127.0.0.1:13000 is already in use.

These ports are used by Redis for different purposes.

  • port 11000: Used by the Redis cache instance to store frequently accessed data and improve application performance.

  • port 13000: Used by the Redis queue instance to manage background tasks and asynchronous operations.

This Address already in use issue usually occurs if previous bench processes didn’t shut down properly.

In my case, i forgot to close bench before shut down my machine.

Solution:

1. Identify Which Processes Are Using the Ports


sudo lsof -i :11000

sudo lsof -i :13000

This shows which process (and its PID) is currently using the port.

2. Kill the Conflicting Processes


sudo kill <PID1> <PID2> <PID3> .....

Frees up the ports so bench start can use them.

This ensures Redis starts correctly and Frappe can utilize caching and queuing systems without issues.

3. Restart the Bench


bench start

With the ports now free and available, the bench should start normally.

Part 2: Fixing Bench Start Crashes via Cache Clearing

Sometimes bench start crashes due to corrupted cache content.

1. Clear Browser Cache


bench --site your-site-name clear-website-cache

The command clear-website-cache:

  1. Browser-level, for web display.

  2. Clears browser cache (HTML, CSS, JS, images) for a website.

  3. Fixes display issues or forces browser to load latest site files.

  4. Clears your browser cache just in case you have cached content that may be causing this problem.

2. Clear Backend Cache


bench --site your-site-name clear-cache

The command clear-cache:

  1. it’s Application-level, for Frappe/ERPNext.

  2. Clears internal caches (metadata, doctypes) in Frappe-based apps like ERPNext, after code or config changes to ensure app uses latest data.

  3. Sometimes when you make changes in code or config (like modifying hooks, custom fields), Frappe still uses old data from memory. This can cause strange errors or crashes when starting the bench.

3. Restart Bench


bench start

  • Always shut down bench properly using Ctrl + c.

  • Use lsof to detect what’s taken ports.

  • Cache can cause strange issues, clear it regularly while developing.

  • the port 11000 or 13000 may change based on your server or the configurations, they are not constant.