Apache multiplies and stops giving content. How to treat?

Question

linux

The server for the last 3 days began to fall, giving 502 errors after 2-3 hours. In httpd logs:

[Mon Jul 31 11:56:24 2017] [notice] Apache/2.2.15 (Unix) mod_fastcgi/2.4.6 mod_rpaf/0.6 PHP/5.3.29 configured -- resuming normal operations
[Mon Jul 31 11:56:25 2017] [error] server reached MaxClients setting, consider raising the MaxClients setting
[Mon Jul 31 11:56:35 2017] [notice] caught SIGTERM, shutting down
[Mon Jul 31 11:56:36 2017] [notice] Apache/2.2.15 (Unix) mod_fastcgi/2.4.6 mod_rpaf/0.6 PHP/5.3.29 configured -- resuming normal operations
zend_mm_heap corrupted
[Mon Jul 31 12:31:19 2017] [notice] child pid 27463 exit signal Segmentation fault (11)
zend_mm_heap corrupted
zend_mm_heap corrupted
[Mon Jul 31 12:45:07 2017] [error] server reached MaxClients setting, consider raising the MaxClients setting
[Mon Jul 31 13:18:16 2017] [notice] child pid 4921 exit signal Segmentation fault (11)
[Mon Jul 31 13:56:15 2017] [notice] child pid 32413 exit signal Segmentation fault (11)
zend_mm_heap corrupted
[Mon Jul 31 15:01:39 2017] [notice] caught SIGTERM, shutting down
[Mon Jul 31 15:01:40 2017] [notice] Apache/2.2.15 (Unix) mod_fastcgi/2.4.6 mod_rpaf/0.6 PHP/5.3.29 configured -- resuming normal operations
zend_mm_heap corrupted
zend_mm_heap corrupted
[Mon Jul 31 15:29:05 2017] [error] server reached MaxClients setting, consider raising the MaxClients setting
zend_mm_heap corrupted
[Mon Jul 31 16:00:09 2017] [notice] child pid 18382 exit signal Segmentation fault (11)
[Mon Jul 31 16:02:02 2017] [notice] child pid 17800 exit signal Segmentation fault (11)
[Mon Jul 31 16:19:12 2017] [notice] child pid 15365 exit signal Segmentation fault (11)
zend_mm_heap corrupted
[Mon Jul 31 16:33:11 2017] [notice] child pid 15653 exit signal Segmentation fault (11)

RAM 64GB on the server, 30GB for mysql given.
Apache is configured like this:

<IfModule mpm_prefork_module>
  StartServers       2
  MinSpareServers    2
  MaxSpareServers   20
  ServerLimit        32
  MaxClients         32
  MaxRequestsPerChild 1000
</IfModule>

Restart httpd and everything works. Where to dig? thanks in advance

Answer 1

Dig towards the MPM worker.
If you continue to use prefork: MaxCLients
calculate based on observations how much each process consumes on average, so that MaxClients * AvgMemoryPerProcess < TotalFreeMemory
StartServers, MinSpareServers, MaxSpareServers,ServerLimit set to MaxClients
Little?)