~~NOTOC~~
====== LiteSpeed Kills Apps Using Recycled PIDs ======
A small ''pid_max'' value may cause applications to be accidentally killed when they are using a recycled PID.

===== Example =====
This log shows that LiteSpeed killed MySQL:
  [Wed Mar 20 04:11:42 2019] SIGTERM to mysqld (12289) by litespeed (6133),0,99 <- systemd (1),0,0
  [Wed Mar 20 04:11:49 2019] SIGTERM to mysqld (12289) by mysqld (12289),994,991 <- mysqld_safe (12121),0,0 <- systemd (1),0,0
  
If you check ''/proc/sys/kernel/pid_max'' you may find ''kernel.pid_max = 32768''.

''32768'' is too small for some situations, particularly where PIDs are used up very fast and recycled quickly. For example, LiteSpeed may try to kill an unused lsphp process, but that PID may already have been recycled and reused as a MySQL (or other application) PID. When LiteSpeed kills the process, MySQL is killed unintentionally.

===== Solution =====
Increase ''pid_max'' from ''32768'' to a larger number, such as ''1048576'', like so:
  sysctl kernel.pid_max
  kernel.pid_max = 32768
  sysctl -w kernel.pid_max=1048576
  kernel.pid_max = 1048576
 
**NOTE**:Sometimes the CRIU feature may cause similar trouble when it resets the PID to restore a process. This causes the PID to be reused too quickly, and can be a problem even with a large ''pid_max'' setting.