Docker container exits after custom entrypoint and original entrypoint execution

Question

I'm encountering an issue with my Docker setup where the container exits unexpectedly after executing a custom entrypoint script and the original entrypoint provided by the base image.
Dockerfile:

FROM pimcore/pimcore:php8.2-latest

ENV PATH="./vendor/bin:${PATH}" \
    NGINX_SERVER_NAME="prod" \
    PHP_OPCACHE_VALIDATE_TIMESTAMPS="0" \
    PHP_OPCACHE_MAX_ACCELERATED_FILES="6000" \
    PHP_OPCACHE_MEMORY_CONSUMPTION="128" \
    PHP_FPM_PM_MAX_CHILDREN=30 \
    PHP_FPM_PM_START_SERVERS=15 \
    PHP_FPM_PM_MIN_SPARE_SERVERS=15 \
    PHP_FPM_PM_MAX_SPARE_SERVERS=25 \
    PHP_FPM_PM_MAX_REQUESTS=500 
    # PHP_MEMORY_LIMIT=512M

COPY ./ /var/www/html
COPY ../docker/php/www.conf /usr/local/etc/php-fpm.d/www.conf

RUN find /var/www/html -print | xargs --max-args=1 --max-procs=10000 -i chown -R 33:33 "{}" | true

COPY pimcore/configure_memory.sh /usr/local/bin/
RUN chmod +x /usr/local/bin/configure_memory.sh

ENTRYPOINT ["/usr/local/bin/configure_memory.sh", "/usr/local/bin/docker-php-entrypoint"]

configure_memory.sh:

#!/bin/bash

echo "Configuring memory..."

# Perform any additional checks or configurations here
if [ "$(awk '/MemTotal/ {print $2}' /proc/meminfo)" -ge 16000000 ]; then
    echo "Setting memory_limit to 512M"
    echo "memory_limit = 512M" >> /usr/local/etc/php/conf.d/20-pimcore.ini
    #modify ENV variables
else
    echo "Setting memory_limit to 256M"
    echo "memory_limit = 256M" >> /usr/local/etc/php/conf.d/20-pimcore.ini
     #modify ENV variables
fi

echo "Executing the original command: $@"

# Execute the CMD of the Docker image
exec "$@"

The container exits with code 0 after executing both the custom entrypoint script (configure_memory.sh) and the original entrypoint (docker-php-entrypoint).

Please note that I don't want to override the original image CMD and ENTRYPOINT. I want to first just execute the custom configure_memory.sh script at runtime to properly assign the memory_limit and the the original image CMD and ENTRYPOINT to continue. The reason for this is that I use the same image on two different app services—one with 16GB of memory and the other with 3.5GB. I need to dynamically configure the memory_limit based on the available memory during runtime.

Is there a better way to configure the **memorylimit***, max_*children( and the other variables) for this scenario, or am I on the right track with the current approach?

Answer 1

The ENTRYPOINT documentation notes

If CMD is defined from the base image, setting ENTRYPOINT will reset CMD to an empty value. In this scenario, CMD must be defined in the current image to have a value.

You need to find the Dockerfile for the base image, or docker inspect it to find its entrypoint. For this image, its Docker Hub page points at a GitHub repository that contains a Dockerfile. The pimcore_php_default stage ends with

CMD ["php-fpm"]

and you need to repeat this in your own Dockerfile. (Note that stage does not seem to obviously declare an ENTRYPOINT.)