PHP-FPM Configuration Tips and Tricks

PHP-FPM Tip 1. – PHP-FPM Configuration files
Normally PHP-FPM configuration files are located on /etc/php-fpm.conf file and /etc/php-fpm.d path. This is normally excellent start and all pool configs goes to /etc/php-fpm.d directory. You need to add following include line on your php-fpm.conf file:
include=/etc/php-fpm.d/*.conf
PHP-FPM Tip 2. – PHP-FPM Global Configuration Tweaks
Set up emergency_restart_threshold, emergency_restart_interval and process_control_timeout. Default values for these options are totally off, but I think it’s better use these options example like following:
emergency_restart_threshold 10
emergency_restart_interval 1m
process_control_timeout 10s
What this mean? So if 10 PHP-FPM child processes exit with SIGSEGV or SIGBUS within 1 minute then PHP-FPM restart automatically. This configuration also sets 10 seconds time limit for child processes to wait for a reaction on signals from master.
PHP-FPM Tip 3. – PHP-FPM Pools Configuration
With PHP-FPM it’s possible to use different pools for different sites and allocate resources very accurately and even use different users and groups for every pool. Following is just example configuration files structure for PHP-FPM pools for three different sites (or actually three different part of same site):
/etc/php-fpm.d/site.conf
/etc/php-fpm.d/blog.conf
/etc/php-fpm.d/forums.conf
Just example configurations for every pool:
/etc/php-fpm.d/site.conf
[site]
listen = 127.0.0.1:9000
user = site
group = site
request_slowlog_timeout = 5s
slowlog = /var/log/php-fpm/slowlog-site.log
listen.allowed_clients = 127.0.0.1
pm = dynamic
pm.max_children = 5
pm.start_servers = 3
pm.min_spare_servers = 2
pm.max_spare_servers = 4
pm.max_requests = 200
listen.backlog = -1
pm.status_path = /status
request_terminate_timeout = 120s
rlimit_files = 131072
rlimit_core = unlimited
catch_workers_output = yes
env[HOSTNAME] = $HOSTNAME
env[TMP] = /tmp
env[TMPDIR] = /tmp
env[TEMP] = /tmp
/etc/php-fpm.d/blog.conf
[blog]
listen = 127.0.0.1:9001
user = blog
group = blog
request_slowlog_timeout = 5s
slowlog = /var/log/php-fpm/slowlog-blog.log
listen.allowed_clients = 127.0.0.1
pm = dynamic
pm.max_children = 4
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 3
pm.max_requests = 200
listen.backlog = -1
pm.status_path = /status
request_terminate_timeout = 120s
rlimit_files = 131072
rlimit_core = unlimited
catch_workers_output = yes
env[HOSTNAME] = $HOSTNAME
env[TMP] = /tmp
env[TMPDIR] = /tmp
env[TEMP] = /tmp
/etc/php-fpm.d/forums.conf
[forums]
listen = 127.0.0.1:9002
user = forums
group = forums
request_slowlog_timeout = 5s
slowlog = /var/log/php-fpm/slowlog-forums.log
listen.allowed_clients = 127.0.0.1
pm = dynamic
pm.max_children = 10
pm.start_servers = 3
pm.min_spare_servers = 2
pm.max_spare_servers = 4
pm.max_requests = 400
listen.backlog = -1
pm.status_path = /status
request_terminate_timeout = 120s
rlimit_files = 131072
rlimit_core = unlimited
catch_workers_output = yes
env[HOSTNAME] = $HOSTNAME
env[TMP] = /tmp
env[TMPDIR] = /tmp
env[TEMP] = /tmp
So this is just example howto configure multiple different size pools.
PHP-FPM Tip 4. – PHP-FPM Pool Process Manager (pm) Configuration
Best way to use PHP-FPM process manager is use dynamic process management, so PHP-FPM processes are started only when needed. This is almost same style setup than Nginx worker_processes and worker_connections setup. So very high values does not mean necessarily anything good. Every process eat memory and of course if site have very high traffic and server lot’s of memory then higher values are right choise, but servers, like VPS (Virtual Private Servers) memory is normally limited to 256 Mb, 512 Mb, 1024 Mb. This low RAM is enough to handle even very high traffic (even dozens of requests per second), if it’s used wisely.
It’s good to test how many PHP-FPM processes a server could handle easily, first start Nginx and PHP-FPM and load some PHP pages, preferably all of the heaviest pages. Then check memory usage per PHP-FPM process example with Linux top or htop command. Let’s assume that the server has 512 Mb memory and 220 Mb could be used for PHP-FPM, every process use 24 Mb RAM (some huge content management system with plugins can easily use 20-40 Mb / per PHP page request or even more). Then simply calculate the server max_children value:
220 / 24 = 9.17
So good pm.max_children value is 9. This is based just quick average and later this could be something else when you see longer time memory usage / per process. After quick testing it’s much easier to setup pm.start_servers value, pm.min_spare_servers value and pm.max_spare_servers value.
Final example configuration could be following:
pm.max_children = 9
pm.start_servers = 3
pm.min_spare_servers = 2
pm.max_spare_servers = 4
pm.max_requests = 200
Max request per process is unlimited by default, but it’s good to set some low value, like 200 and avoid some memory issues. This style setup could handle large amount of requests, even if the numbers seems to be small.

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