Recently I've had to confront to php-fpm issue with constantly growing of available active process. It was reaching max_children and then restarted.
The graph shows "active processes" value from pool status from three servers (round robin balance).
pm.max_children = 100 pm.start_servers = 20 pm.min_spare_servers = 5 pm.max_spare_servers = 35 pm.max_requests = 2000
At 01AM I changed configuration to:
pm.max_children = 500 pm.max_requests = 500
This pool serves about 4k req/min (for all servers). I must admit other pools are working normally with the same settings (biggest pool serves ~12k req/min).
What could be a reason for such weired behavior?