Single PHP FPM container with Caddy

.dockerignore

/vendor
/docker
/Dockerfile

Caddyfile

0.0.0.0:{$PORT}

root /usr/src/app/public

fastcgi / /var/run/php-fpm.sock php

rewrite {
    to {path} /index.php?{query}
}

supervisor {
    command php-fpm
    restart_policy always
    redirect_stdout stdout
    redirect_stderr stderr
}

errors stdout

Dockerfile

FROM php:7.4-fpm-alpine

COPY --from=composer:latest /usr/bin/composer /usr/bin/composer
COPY --from=wizbii/caddy /caddy /usr/local/bin/caddy

RUN apk add --no-cache autoconf openssl-dev g++ make pcre-dev icu-dev zlib-dev libzip-dev && \
    docker-php-ext-install bcmath intl opcache zip sockets && \
    apk del --purge autoconf g++ make && \
    mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"

WORKDIR /usr/src/app

COPY composer.json composer.lock ./

RUN composer install --no-dev --optimize-autoloader --no-scripts --no-plugins --prefer-dist --no-progress --no-interaction

COPY . .

ENV APP_ENV=prod
ENV PORT=80

RUN caddy -validate -conf=docker/Caddyfile && \
    cp docker/php-fpm.conf /usr/local/etc/php-fpm.d/zz-docker.conf && \
    php bin/console cache:warmup && \
    chmod -R 777 var/cache var/log

EXPOSE 80

CMD ["caddy", "--conf", "docker/Caddyfile", "--log", "stdout"]

php-fpm.conf

[global]
daemonize = no

[www]
listen = /var/run/php-fpm.sock

Question: what magic step causes php-fpm to start here? Isn't the CMD section overriding php:7.4-fpm-alpine behaviour? I'm asking because in my case only Caddy started, not PHP. I used supervisord to start php-fpm for me. I wonder if there is a better way.

The command php bin/console cache:warmup at the RUN keyword
it is running using an UNIX socket file /var/run/php-fpm.sock

This is caddy that is starting php-fpm, using it's supervisor plugin.

If you are using Caddy V2, I recommend you to have a look at this gist: https://gist.github.com/Baldinof/9adf039d9edabc0001dea3abafb6764f