Multiple PHP Pools

PHP has gotten phenomenal to work with over the last few years.There have been so many improvements - both to the language itself and, in my humble opinion, the developer experience in using the language every day.

I'm a terrible hypeman for anything but if you're interested in the current state of PHP, I'd highly recommend reading PHP in 2020 by Brent Roose.

One of the new features of PHP that I wanted to experiment with was preloading but I had several sites on my Rasperry Pi and they didn't all depend on the same code, so I needed to seperate my instances.

Enter pools

PHP pools are seperate processes that can each be used to serve a subset of requests. You'll probably already be using the default pool at the moment:

server {
    ###

    server_name www.test;

    location ~ \.php$ {
        fastcgi_pass unix:/var/run/php/php7.4-fpm.sock;
    }

    ###
}

On Ubuntu, PHP pool configuration is located at /etc/php/7.4/fpm/pool.d/. I'd start by copying the template that's there for my new pool.

cd /etc/php/7.4/fpm/pool.d
sudo cp www.conf www2eb.conf

You'll then want to edit this file and update, at minimum, a setting or two.

sudo nano www2eb.conf

Update the name of the pool:

; Start a new pool named 'www'.
; the variable $pool can be used in any directive and will be replaced by the
; pool name ('www' here)
[www2eb]

If you want to change the user that owns the pool, update the following:

; Unix user/group of processes
; Note: The user is mandatory. If the group is not set, the default user's group
; will be used.
user = poolowner

Lastly, we need to give it a different socket so we can send requests to it via NGINX

; Note: This value is mandatory.
listen = /run/php/php7.4-fpm.poolowner.sock

Now that we've updated the PHP pools, we need to update our NGINX server block to point to the correct socket:

server {
    ###

    location ~ \.php$ {
        fastcgi_pass unix:/var/run/php/php7.4-fpm.poolowner.sock;
    }

    ###
}

We've now made all of the updates that we need, it's time to restart our services:

sudo service nginx restart && sudo service php-7.4-fpm restart

You can now check that your new PHP pool is working by visiting your site in a browser.