[users@httpd] HTTPD 2.4.6 - httpd process hanging intermittently

[gauty henley <ga...@comcast.net>]

Hello,

First of all I believe this is the right place to ask the apache related questions. Thank you for the help in advance.

I am facing some issues with httpd process getting hung intermittently. While troubleshooting I could see that some of the semaphore counts is greater than zero. I could make it work by clearing those semID's. But wanted to understand what's causing it.

Below is some of the information.

Version:
Server version: Apache/2.4.6 (CentOS)


ipcs -s -i 45187195
Semaphore Array semid=45187195
uid=48 gid=48 cuid=0 cgid=0
mode=0600, access_perms=0600
nsems = 1
otime = Tue Feb 23 12:14:35 2021
ctime = Mon Feb 8 09:45:38 2021
semnum value ncount zcount pid
0 0 1 0 19944

ps -ef | grep 19944
root 2409 19130 0 17:06 pts/0 00:00:00 grep --color=auto 19944
apache 19944 24691 0 12:14 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND

ipcs -us
------ Semaphore Status --------
used arrays = 128
allocated semaphores = 128

ipcs -ls
------ Semaphore Limits --------
max number of arrays = 256
max semaphores per array = 250
max semaphores system wide = 64000
max ops per semop call = 32
semaphore max value = 32767

ps -efL|grep httpd | awk '{print $2}' | uniq -c
60 2471
1 2509
80 12617
202 19944
1 20149
76 21108
1 24691
1 24692
75 28558
76 32344

wget localhost
--2021-02-23 17:10:24-- http://localhost/
Resolving localhost (localhost)... 127.0.0.1
Connecting to localhost (localhost)|127.0.0.1|:80...

tcp6 512 0 :::80 :::* LISTEN 19944/httpd

nc -zv localhost 80
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 127.0.0.1:80.
Ncat: 0 bytes sent, 0 bytes received in 1.01 seconds

1.During this time the number of connection spikes up before process get hang. 
2. No errors or anything in logs. It just hangs and stop accepting traffic.
3. I did try gdb and strace but nothing helpful in there.

Appreciate any pointers on why this is causing. Please let me know if any additional questions,

Thanks- Gauty