How to limit the amount of memory httpd is using on CentOS 7 with Cgroups

CentOS 7, introduced something called CGroups, or control groups which has been in the stable kernel since about 2006. The systemD unit is made of several parts, systemD unit resource controllers can be used to limit memory usage of a service, such as httpd control group in systemD.

# Set Memory Limits for a systemD unit
systemctl set-property httpd MemoryLimit=500MB

# Get Limits for a systemD Unit
systemctl show -p CPUShares 
systemctl show -p MemoryLimit

Please note that OS level support is not generally provided with managed infrastructure service level, however I wanted to help where I could hear, and it shouldn’t be that difficult because the new stuff introduced in SystemD and CGroups is much more powerful and convenient than using ulimit or similar.