"An unexpected error occurred" - Every few hits

[cwldev]

How Shlink is set-up

• Shlink Version: v2.10.0
• PHP Version: Running in Docker
• How do you serve Shlink: Docker Image
• Database engine used: MariaDB
• Server is behind an nginx proxy (based inside LinuxServer/swag)

Summary

Previous versions appeared to be ok. Started noticing this recently after updates.

Current behavior

Possibly 50% or more of short link hits yield an error "An unexpected error occurred" - on refresh, the link does resolve.

Link creation by way of shlink-web encounters no issues creating short links.

Expected behavior

I expect all links to redirect and no errors.

How to reproduce

Not sure as this doesn't appear to be configuration-related.
Perhaps there are some things I could look for?

[acelaya]

Could you check the logs around the time this error happens? For the docker image, los are in the standard output.

[acelaya]

I have actually managed to reproduce it. I have a suspicion of what could be causing this.

Just to make sure it's the same. Can you check in the logs if you find "MySQL server has gone away"?

[cwldev]

Yes, sorry.. there's a lot on the log but I notice the line:

Next Doctrine\DBAL\Exception\ConnectionLost: An exception occurred while executing a query: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away in /etc/shlink/vendor/doctrine/dbal/src/Driver/API/MySQL/ExceptionConverter.php:106

And the log ends with:
[2021-12-20T22:23:37.529634+00:00] [496fda53-e901-466e-8273-8d71c6f60588] Access.ERROR - 192.168.1.202 - - "GET /8MrpJ HTTP/1.1" 500 28
[2021-12-20T22:23:37.567762+00:00] [496fda53-e901-466e-8273-8d71c6f60588] Access.INFO - 192.168.1.202 - - "GET /favicon.ico HTTP/1.1" 200 16958

Refresh, link works.

[acelaya]

I have found the root cause for this. It's something I already "fixed" several versions ago, but it turns out I only applied a partial fix, mitigating the issue so that it recovers after failing once, instead of preventing the fail completely.

The weird thing is that it has been there since a lot of time ago. It's weird that nobody noticed before.

[acelaya]

I have just released v2.10.1

The docker image will be available once this job finishes: https://github.com/shlinkio/shlink/runs/4595524058?check_suite_focus=true