share the experience if he/she happened to meet the same issue

Well, duh, mixing DBI and threads in the wrong way causes crashes, exactly those that you experienced. You are not alone.

Do you feel better now?

learned about the solution

Create threads before calling DBI->connect(), as explained in the fine manual.

I'll try to find a way to make log4perl get new connection during new threads.

CHANGING DBH CONNECTIONS (POOLING) sounds promising.

Alexander