FPM
From DWIKI
FastCGI Process Manager
Links
Monitoring PHP-FPM
HOWTO
Configuring number of servers
dynamic - the number of child processes are set dynamically based on the following directives: pm.max_children - the maximum number of children that can be alive at the same time.
pm.start_servers - the number of children created on startup. this value must not be less than min_spare_servers and not greater than max_spare_servers.
pm.min_spare_servers - the minimum number of children in 'idle' state (waiting to process). If the number of 'idle' processes is less than this number then some children will be created.
pm.max_spare_servers - the maximum number of children in 'idle' state (waiting to process). If the number of 'idle' processes is greater than this number then some children will be killed.
FAQ
proxy_fcgi AH01071: Got error 'Primary script unknown'
The fcgi 404
AH01079: failed to make connection to backend: httpd-UDS
USB = Unix Domain Socket, look for logging/config about the socket involved
Show php-fpm config
php-fpm8.0 -tt