Docker Entrypoint script cannot get $DB_PORT_3306_TCP_ADDR environment variable - docker

Question

I have the following Dockerfile:
FROM php:5.6-apache
MAINTAINER pc_magas#openmailbox.org
EXPOSE 80
RUN apt-get update && apt-get install -y \
libjpeg-dev \
libfreetype6-dev \
libgeoip-dev \
libpng12-dev \
libldap2-dev \
zip \
mysql-client \
&& rm -rf /var/lib/apt/lists/*
RUN docker-php-ext-configure gd --with-freetype-dir=/usr --with-png-dir=/usr --with-jpeg-dir=/usr \
&& docker-php-ext-configure ldap --with-libdir=lib/x86_64-linux-gnu/ \
&& docker-php-ext-install -j$(nproc) gd mbstring mysql pdo_mysql zip ldap opcache
RUN pecl install APCu geoip
ENV PIWIK_VERSION 3.0.1
RUN curl -fsSL -o piwik.tar.gz \
"https://builds.piwik.org/piwik-${PIWIK_VERSION}.tar.gz" \
&& curl -fsSL -o piwik.tar.gz.asc \
"https://builds.piwik.org/piwik-${PIWIK_VERSION}.tar.gz.asc" \
&& export GNUPGHOME="$(mktemp -d)" \
&& gpg --keyserver ha.pool.sks-keyservers.net --recv-keys 814E346FA01A20DBB04B6807B5DBD5925590A237 \
&& gpg --batch --verify piwik.tar.gz.asc piwik.tar.gz \
&& rm -r "$GNUPGHOME" piwik.tar.gz.asc \
&& tar -xzf piwik.tar.gz -C /usr/src/ \
&& rm piwik.tar.gz
COPY php.ini /usr/local/etc/php/php.ini
RUN curl -fsSL -o /usr/src/piwik/misc/GeoIPCity.dat.gz http://geolite.maxmind.com/download/geoip/database/GeoLiteCity.dat.gz \
&& gunzip /usr/src/piwik/misc/GeoIPCity.dat.gz
COPY docker-entrypoint.sh /entrypoint.sh
# WORKDIR is /var/www/html (inherited via "FROM php")
# "/entrypoint.sh" will populate it at container startup from /usr/src/piwik
VOLUME /var/www/html
ENV PIWIK_DB_HOST ""
ENV PIWIK_DB_PORT ""
ENV PIWIK_DB_USER ""
ENV PIWIK_DB_PASSWORD ""
ENV PIWIK_DB_NAME ""
#Create backup and restore foolders
RUN mkdir /var/backup && \
chmod 665 /var/backup && \
mkdir /var/restore && \
chmod 665 /var/restore
#Export Backup Folder
VOLUME /var/backup
#Export restore foolder
VOLUME /var/restore
COPY backup.php /tmp/backup.php
RUN cp /tmp/backup.php /usr/local/bin/piwik_backup && \
chown root:root /usr/local/bin/piwik_backup && \
chmod 733 /usr/local/bin/piwik_backup && \
rm -rf /tmp/backup
ENTRYPOINT ["/entrypoint.sh"]
CMD ["/usr/sbin/apache2ctl", "-D", "FOREGROUND"]
That uses the following script as entrypoint:
#!/bin/bash
if [ ! -e piwik.php ]; then
cp -R /usr/src/piwik/* /var/www/html
chown -R www-data:www-data .
fi
: ${PIWIK_DB_HOST:=$DB_PORT_3306_TCP_ADDR}
echo "Mariadb Addr:"$DB_PORT_3306_TCP_ADDR
: ${PIWIK_DB_PORT:=${DB_PORT_3306_TCP_PORT}}
COUNTER=0
echo "Waiting for mysql to start at ${PIWIK_DB_HOST} using port ${PIWIK_DB_PORT}..."
while ! mysqladmin ping -h"$PIWIK_DB_HOST" -P $PIWIK_DB_PORT --silent; do
if [ $COUNTER -gt 10 ] ; then
exit 1
fi
echo "Connecting to ${PIWIK_DB_HOST} Failed"
COUNTER=$[COUNTER+1]
sleep 1
done
echo "Setting up the database connection info"
: ${PIWIK_DB_USER:=${DB_ENV_MYSQL_USER:-root}}
: ${PIWIK_DB_NAME:=${DB_ENV_MYSQL_DATABASE:-'piwik'}}
if [ "$PIWIK_DB_USER" = 'root' ]; then
: ${PIWIK_DB_PASSWORD:=$DB_ENV_MYSQL_ROOT_PASSWORD}
else
: ${PIWIK_DB_PASSWORD:=$DB_ENV_MYSQL_PASSWORD}
fi
if ! mysql -h"$PIWIK_DB_HOST" -P $PIWIK_DB_PORT -u ${PIWIK_DB_USER} -p${PIWIK_DB_PASSWORD} -e ";" ; then
echo "The user does not exist to the mysql server: ${PIWIK_DB_HOST}"
exit 1
fi
php console config:set --section="database" --key="host" --value=${PIWIK_DB_HOST}
php console config:set --section="database" --key="port" --value=${PIWIK_DB_PORT}
php console config:set --section="database" --key="username" --value=${PIWIK_DB_USER}
php console config:set --section="database" --key="password" --value=${PIWIK_DB_PASSWORD}
php console config:set --section="database" --key="tables_prefix" --value="piwik_"
php index.php
exec "$#"
But for some reason The entrypoint script cannot find the enviromental variables provided by mariadb container such as the DB_PORT_3306_TCP_ADDR providing the connection to the mariadb server.
I use the following commands in order to run the images into the containers containers:
docker run --name piwikdb --volume $(pwd)/volumes/db:/var/lib/db \
-e MYSQL_ROOT_PASSWORD=123 -d mariadb
docker run --volume $(pwd)/volumes/piwik:/var/www/data --link piwikdb:mysql \
-p 8081:80 -t ^hash of the fresly build image^
I tried to troubleshoot it, but I cannot figure out why that happens.

Answer 1

This is not how you want to do linking.
The correct, supported, way, is one of the following.
Use docker-compose
If you use docker-compose, you would name your database service (say, db), and then your other containers can be told to connect to db as if it were a hostname.
You can use env_file in docker-compose.yml to specify a file with parameters such as database name, mariadb port, authentication info, and so on. Each container can load the same env_file.
Use a docker network
If you prefer to run containers without using compose, just make sure they are on the same network, like this:
docker network create myapp
docker run --name piwikdb --volume $(pwd)/volumes/db:/var/lib/db \
-e MYSQL_ROOT_PASSWORD=123 -d --network myapp mariadb
docker run --volume $(pwd)/volumes/piwik:/var/www/data \
--network myapp -p 8081:80 -t ^hash of the fresly build image^
If all containers are on the same network, then as with docker-compose, you can just tell your piwik container to use "piwikdb" as the server (i.e. the container name of your other container).