atws/docker-wordpress repository overview

⁠WordPress Docker Container

Lightweight WordPress container with & based on Alpine Linux 3.23

WordPress version currently installed: 7.1.0

• Used in production for my own sites, making it stable, tested and up-to-date
• PHP-FPM pool sized automatically from the container's memory limit, so the same image is safe from a 700Mi container up to 8Gi
• Best to be used with Amazon Cloudfront as SSL terminator and CDN
• Built on the lightweight Alpine Linux distribution
• Can safely be updated without losing data
• Fully configurable because wp-config.php uses the environment variables you can pass as a argument to the container

⁠Usage

See docker-compose.yml⁠ how to use it in your own environment.

docker-compose up

Or

docker run -d -p 80:80 -v <volumename>:/var/www/html/wp-content \
-e "DB_HOST=db" \
-e "DB_NAME=wordpress" \
-e "DB_USER=wp" \
-e "DB_PASSWORD=secret" \
-e "TABLE_PREFIX=only_if_not_wp_" \
-e "FS_METHOD=direct" \
-e "DISABLE_AUTO_CHOWN=true" \
-e "DISABLE_AUTO_DB_UPDATE=true" \
atws/docker-wordpress:latest

⁠PHP-FPM tuning

pm.max_children is derived at startup from the container's own memory limit (the cgroup limit Kubernetes/Docker enforces), because a single static value cannot be right for both a 700Mi and an 8Gi container. The computed value is logged on every boot:

php-fpm sizing: pm=dynamic pm.max_children=7 (container memory limit 700MB - 192MB reserved, / 64MB per worker)

Roughly (container_limit_MB - reserved) / per_worker, clamped to 2..64, where per_worker defaults to half of PHP_MEMORY_LIMIT. Measured across live pods, a steady-state worker holds 25-45MB of unreclaimable memory against a 128M limit - opcache and the binaries are shared, and are counted in the reserve rather than per worker - so half the limit is a realistic budget with headroom.

Because the two are linked, raising PHP_MEMORY_LIMIT buys fewer workers rather than the same number of hungrier ones:

If no container memory limit is set at all, the pool falls back to 16 workers and logs a warning - set resources.limits.memory so it can be sized properly.

Everything is overridable per container:

Prefer these over mounting a .user.ini into the docroot. .user.ini is PHP_INI_PERDIR, so it overrides both php.ini and PHP_MEMORY_LIMIT — a site that mounts one silently defeats the setting above and hides the real per-worker cost from the sizing, which is how sites end up OOM-killed.

If a site queues requests rather than crashing, raise the container's memory limit; the pool resizes itself on the next restart.

⁠WP-CLI

This image includes wp-cli⁠ which can be used like this:

docker exec <your container name> /usr/local/bin/wp --path=/var/www/html <your command>

⁠Inspired by

• https://hub.docker.com/_/wordpress/⁠
• https://codeable.io/wordpress-developers-intro-to-docker-part-two/⁠
• https://github.com/TrafeX/docker-php-nginx/⁠
• https://github.com/etopian/alpine-php-wordpress/⁠
• https://github.com/Trafex/docker-wordpress/⁠
• https://github.com/raulr/nginx-wordpress-docker/⁠
• and Kris!