2013: "Lost connection to MySQL server at 'handshake: reading inital communication packet', system error: 115" when trying to connect

Question

Creating an image for mariadb dump. Cannot establish connection to mariadb container. I have a container running MariaDB. I am developing my image for creating MySQL dump of the database periodically. Connection between mariadump container and MariaDB container could not be established.

Docker-Compose

version: '3.3'
services:
    db:
        # image: 'mariadb'
        build: ./mariadbimage
        container_name: MariaDB
        volumes:
            - db_data:/var/lib/mysql
            # - ./etc/localtime:/etc/localtime:ro
            # - ./opt/mysql/backup:/opt/mysql/backup
        ports:  
            - "3306:3306"
        restart: always
        environment:   
            MYSQL_ROOT_PASSWORD: wordpress
            MYSQL_DATABASE: wordpress
            MYSQL_USER: wordpress
            MYSQL_PASSWORD: wordpress

    mariadump:
        container_name: MariaDump
        build: ./mariadumpimage
        environment:
            TZ: Europe/Berlin

        volumes:
            - ./ssh:/root/.ssh
        depends_on:
            - db
        links:
            - db

MariaDump Dockerfile

FROM mariadb/server
RUN apt-get update && apt-get -y install cron curl openssh-client 
ENV TINI_VERSION v0.17.0
ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini /tini
RUN chmod +x /tini

ADD scripts /usr/local/bin/
RUN chmod 0755 /usr/local/bin/mariadumper.sh /usr/local/bin/docker-entrypoint.sh

ENTRYPOINT ["/tini", "-e", "143", "--", "docker-entrypoint.sh"]

Mariadump Entrypoint

MYSQL_USER=wordpress
MYSQL_PASSWORD=wordpress
MYSQL_HOST=host.docker.internal
MYSQL_PORT=3306

BACKUP_FILE=/var/backups/$(date +"%Y-%m-%d-%H%M%S")_${MYSQL_HOST}_mysqldump

MYSQL_OPTS="-u${MYSQL_USER} -p${MYSQL_PASSWORD} -h${MYSQL_HOST} -P${MYSQL_PORT}"
MYSQLDUMP_OPTS="--single-transaction --routines --triggers"

mysqldump ${MYSQL_OPTS} ${MYSQLDUMP_OPTS} --all-databases >${BACKUP_FILE}
RETVAL=$?

if [ "$RETVAL" == 0 ]; then
  echo Compressing backup using gzip compression method.
  gzip --best ${BACKUP_FILE}*
  RETVAL=$?
fi

if [ "$RETVAL" == 0 ]; then
    echo Backup finished successfully.
    exit 0 
else
    echo Backup failed with errors!
    exit 1
fi

Error:

Got error: 2013: "Lost connection to MySQL server at 'handshake: reading inital communication packet', system error: 115" when trying to connect

Answer 1

If you want to make to containers able to communicate, you should use the networks property.

version: '3.3'
services:
    db:
        # image: 'mariadb'
        build: ./mariadbimage
        container_name: MariaDB
        volumes:
            - db_data:/var/lib/mysql
            # - ./etc/localtime:/etc/localtime:ro
            # - ./opt/mysql/backup:/opt/mysql/backup
        ports:  
            - "3306:3306"
        restart: always
        environment:   
            MYSQL_ROOT_PASSWORD: wordpress
            MYSQL_DATABASE: wordpress
            MYSQL_USER: wordpress
            MYSQL_PASSWORD: wordpress
        networks:
            - my-network-name

    mariadump:
        container_name: MariaDump
        build: ./mariadumpimage
        environment:
            TZ: Europe/Berlin

        volumes:
            - ./ssh:/root/.ssh
        depends_on:
            - db
        links:
            - db
        networks:
            - my-network-name
networks:
    my-network-name:
      driver: bridge

Then containers can send requests to each other using the container-name or id:

http://MariaDB:3306/

As a suggestion, use only snake_case in configuration files.