How it is diagnosed (reproduced or source analysis)?
Source Analysis (we did not reproduce this failure).
Apache didn’t shut-down cleanly. In this case, Apache didn’t close the connections during shut-down, causing remote server (a database in this case) malfunction.
When Apache child that is polling (blocked) on socket, it would be directly killed when received a AP_SIG_GRACEFUL, instead of returning from poll and continue.
Can Errlog anticipate an error msg?
Yes. Errlog can print a msg in a signal handler (sigkill signal).
Is there Error Message?