Bug #117657 [ERROR] [MY-013935] [Server] IO-layer timeout before wait_timeout was reached
Submitted: 10 Mar 16:47 Modified: 12 Mar 14:31
Reporter: Serge Medelice Email Updates:
Status: Not a Bug Impact on me:
None 
Category:MySQL Server Severity:S3 (Non-critical)
Version:8.4.4 OS:Other (Rocky Linux 8)
Assigned to: MySQL Verification Team CPU Architecture:x86 (x86_64 / CPU 2)

[10 Mar 16:47] Serge Medelice 
Description:
After MySQL upgrade from LTS release 8.0.41 to 8.4.4, the following error message is seeing in the mysql server log:
[ERROR] [MY-013935] [Server] IO-layer timeout before wait_timeout was reached
This message repeats itself everyday since the upgrade at no regular time with no related application logs

How to repeat:
Unable to reproduce it
[11 Mar 23:09] MySQL Verification Team 
Hi I upgraded few test setups and I do not see this error in the log. Without a way to reproduce the problem there is not much we can do.
[12 Mar 10:00] Serge Medelice 
Thank you for your response.

I have also upgraded a Rocky Linux 8 test server without seeing this occurrence. I have seen in internet someone getting the same error message though (https://stackoverflow.com/questions/79486567/mysql-my-013935-io-layer-timeout-before-wait-...)
[12 Mar 12:43] MySQL Verification Team 
this is just an informational message that the connection dropped before it was expected to timeout from wait_timeout.

Probably a firewall or vpn, router terminated the connection early.

Consider setting a lower tcp_keepalive_time and see if it helps.
https://tldp.org/HOWTO/TCP-Keepalive-HOWTO/usingkeepalive.html