Apache HTTPD not responding after running for several days (Apache Users)

Hi all,

I'm using Apache HTTPD 2.4.29 and 2.4.33 on Solaris 10 and 11. These HTTPDs were compiled from source with the latest APR, APR-util and PCRE.
Upon starting, the HTTPDs initially run fine. After running for several days to 2 weeks, HTTPD would stop responding. It wouldn't accept any new connections although the processes are running. In the whole period the incoming traffic volumn is low.
When in the "not responding" situation, stopping and then starting the HTTPD would workaround the issue temporarily.

The symptoms are:
1. About 5 HTTPD processes are still running (checked by the "ps -ef" command)
2. The TCP port is still being listened (checked by the "netstat -an | grep LISTEN" command)
3. Any new incoming request would result in a connection in SYN_SENT state (checked by "netstat -an") which usually disappears 1 minute later.

I have several Redhat 6.7 and Solaris 10 and 11 machines, and I find that this problem only occurs on Solaris 10 and 11.

I'd appreciate your help. Thanks in advance.

Regards,
Eric