Re: fcgi unix domain socket/TCP socket question (Apache Users)

Couple of questions ...

Reading this Apache httpd document ...

https://httpd.apache.org/docs/2.4/mod/mod_proxy_fcgi.html

Does the below mean if the max children for a PHP-FPM pool using Unix Domain Sockets is reached then any subsequent PHP-FPM requests for that virtual host utilize a TCP socket? If we have the base www.conf pool configured to use TCP as opposed to Unix Domain Sockets?

SetHandler "proxy:unix:/var/run/php-fpm/something.com.sock|fcgi://something.com/"

No, it doesn’t. It’s not “or”, it’s a pipe telling it what protocol to use. The only part taken in to consideration actually is “fcgi://“ and the rest (something.com/) is not needed and is ignored in this case.

What would be the impact of NOT defining a matching worker for the above config? Like is done in this line on the apache.org documentation page referenced above ..

<Proxy "fcgi://localhost/" enablereuse=on max=10>

Not sure what you mean here. It always must go to a pool, either through TCP or a domain socket.

Occasionally, typically when someone is doing a Wordpress core or plugin upgrade, all PHP-FPM sites cease to load their content. And a reboot is needed to get back to normal. But a large number of PHP-FPM processes get started

seemingly maxing out the "Sethandler" connections. then we see "fcgi" timeouts in log.

Perhaps you have too many workers possible if all pools use their allocation, or a big part of it, at the same time. Consider setting lower limits on pools or sharing a pool?

It shouldn’t be maxing out the connections, more likely your processor is maxed out so connections timeout because the resources aren’t available to service them?

Our goal is to avoid the perceived problem the results from this php-fpm/TCP bug by using Domain Sockets. Any suggestions?

I don’t think domain sockets will fix this, if I’m understanding your issue correctly.

https://blog.cloudflare.com/this-is-strictly-a-violation-of-the-tcp-specification/

Thanks for everyones work on Apache

Nigel B. Peck

Web Technologies and Linux Server Admin Mentor

https://codementor.io/nigelbpeck