Percona: Got an error writing communication packets

Since a few days, two of our php-applications (symfony2) are reporting the following errors in mysql-logs:

[Warning] Aborted connection 253 to db: '$appname' user: '$appname' host: 'localhost' (Got an error writing communication packets)

One or two pages won't render and return a blank 503-error, the rest of the website works fine.

The strange part is that this issue started on one server a few days ago, and this morning a second server is affected. Mysql is running local on each server and is configured to use unix-sockets

What could be the cause of this? No configuration changes to the code or web applications were done.

Things I tried:

• Increase max_allowed_packet from 1M to 16 and 64 -> no success
• Clean the mysql config and reset to default values -> no success
• Increase mysql buffers and caching -> no success

It turned out that mysql wasn't the culprit. In php-fpm request_slowlog_timeout was set to 1s. Increasing this value fixed the errors. It seems that fpm was killing processes because the timeout increased 1 second.