Websites on PHP-FPM are unavailable or loading slowly:

[mahesh]

Question: Websites on PHP-FPM are unavailable or loading slowly: server reached max_children setting (*), consider raising it
Applicable to:
Plesk for Linux
Symptoms
Websites that have PHP handler set as FPM application served by Apache or FPM application served by nginx at Domains > example.com > PHP Settings experience one of the following issues:

load slowly

not accessible (permanently or periodically) with a 50x error in a web-browser:

Code Select Expand

502 Bad Gateway


Code Select Expand

503 Service Temporarily Unavailable


Code Select Expand

504 Gateway Time-out
The following message appears in the PHP-FPM error logfile /var/log/plesk-phpXX-fpm/error.log (where XX is a PHP version used by the websites):

WARNING: [pool example.com] server reached max_children setting (*), consider raising it

The message above is usually accompanied with this error:

unable to read what child say: Bad file descriptor (9)

If nginx is enabled on the server, one of the following error messages may appear in domain's error logfile /var/www/vhosts/system/example.com/logs/proxy_error_log:

[error] 11456#0: *118348 connect() to unix:///var/www/vhosts/system/example.com/php-fpm.sock failed (11: Resource temporarily unavailable) while connecting to upstream, client: 203.0.113.2, server: example.com, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:///var/www/vhosts/system/example.com/php-fpm.sock:", host: "example.com"

[error] 20058#0: *4725139 upstream prematurely closed connection while reading response header from upstream, client: 203.0.113.2, server: example.com, request: "POST /path/to/some/file HTTP/2.0", upstream:




Cause