MariaDB Docker Access denied for user '--password='@'localhost'

The Error

I stumbled across this error message within my MariaDB Docker container logs when trying to initialize using the following docker-compose file (modified from the Vikunja Docs):

services:
  vikunja:
    image: vikunja/vikunja
    environment:
      VIKUNJA_SERVICE_PUBLICURL: http://<the public ip or host where vikunja is reachable>
      VIKUNJA_DATABASE_HOST: db
      VIKUNJA_DATABASE_PASSWORD: changeme
      VIKUNJA_DATABASE_TYPE: mysql
      VIKUNJA_DATABASE_USER: vikunja
      VIKUNJA_DATABASE_DATABASE: vikunja
      VIKUNJA_SERVICE_JWTSECRET: <a super secure random secret>
    ports:
      - 3456:3456
    volumes:
      - ./files:/app/vikunja/files
    depends_on:
      db:
        condition: service_healthy
    restart: unless-stopped
  db:
    image: mariadb:10
    command: --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci
    environment:
      MARIADB_ROOT_PASSWORD: supersecret
      MARIADB_USER: vikunja
      MARIADB_PASSWORD: changeme
      MARIADB_DATABASE: vikunja
    volumes:
      - ./db:/var/lib/mysql
    restart: unless-stopped
    healthcheck:
      test: ["CMD-SHELL", "mysqladmin ping -h localhost -u $$MYSQL_USER --password=$$MYSQL_PASSWORD"]
      interval: 2s
      start_period: 30s

I Googled the message and found nothing. It’s a very odd message, and while I haven’t looked into the Dockerfile, I think a missing environment variable is causing the --password flag to be passed into the --user flag.

So I’m writing this to show how to fix it in case anybody else has this issue.

The Fix

Notice that I updated the environment variable to use MARIADB instead of MYSQL, as this is how it is used in the MariaDB docs.

The healthcheck on the MariaDB container attempts to ping the container with $$MYSQL_USER and $$MYSQL_PASSWORD, which is the cause of this issue.

So either update to $$MARIADB_USER and $$MARIADB_PASSWORD, or remove the healthcheck, and it should work as intended.