Varnish Error: 503 Backend Fetch Failure - Troubleshooting Needed

Backend
1

Help! I’m stuck with a Varnish issue.

I’m new to Varnish and I’m getting a 503 Backend fetch failed error when I try to access my webpage. Here’s what I’ve found:

  • Direct access to Apache (port 8080) works fine
  • Access through Varnish (port 80) fails
  • Varnishlog shows ‘No backend’ error

I’m using:

  • Debian Jessie (minimal) in VirtualBox
  • Apache2 on port 8080
  • Varnish 4.1.5 on port 80

My default.vcl has a single backend and a round-robin director. I’ve set up health checks, but they don’t seem to help.

I’ve tried adjusting timeout values, but the error appears instantly.

Any ideas on what might be causing this? I’m totally stumped!

2

hey Lu_57Read, sounds frustrating. maybe check if varnish is actually running? sometimes it fails silently. try ‘service varnish status’ or look at /var/log/varnish/varnish.log for clues. also, double-check ur backend definition in vcl matches apache’s actual setup

3

hmm, interesting. have you verified that your backend is listening on port 8080? try ‘netstat -tuln’ to check. can you share your vcl setup? could firewall restrictions be affecting comms between varnish and apache?

4

I’ve encountered similar issues before. One often overlooked aspect is SELinux. If it’s enabled, it might be blocking communication between Varnish and Apache. Check its status with ‘sestatus’ and try temporarily disabling it with ‘setenforce 0’ to see if that resolves the issue. Remember to re-enable it afterward if it’s not the root cause.

Additionally, ensure your Apache configuration is correctly set to listen on port 8080. Sometimes, the default configuration files might override your settings. Review /etc/apache2/ports.conf and any relevant virtual host configurations to confirm they align with your intended setup.

Lastly, examine your Varnish startup parameters. Incorrect arguments, particularly those related to memory allocation or backend definition, can lead to this error. Review your Varnish service file or startup script to ensure all parameters are correctly set.