众所周知的“Docker容器看不到彼此”的问题

Question

I checked many forum entries (eg in stackoverflow too) but I still cannot figure out what the problem is with my docker-compose file.

So when I start my application ( content-app ) I got the following exception:

Failed to obtain JDBC Connection; nested exception is java.sql.SQLNonTransientConnectionException: Could not connect to address=(host=content-database)(port=3306)(type=master) : Connection refused (Connection refused)

My application is a Spring boot app that tries to connect to the database, the JDBC URL is

url: jdbc:mariadb://content-database:3306/contentdb?autoReconnect=true

The Spring Boot app works fine as locally (when no docker is used) can connect to the local mariadb.
So the content-app container don't see the content-database container. I read that if I specify a network and I assign the containers to the network then they should be able to connect to each other.

When I connect to the running content-app container then I can telnet to content-database

root@894628d7bdd9:/# telnet content-database 3306
Trying 172.28.0.3...
Connected to content-database.
Escape character is '^]'.
n
5.5.5-10.4.3-MariaDB-1:10.4.3+maria~bionip/4X@wW/�#_9<b[~)N.:ymysql_native_passwordConnection closed by foreign host.

My docker-compose yaml file:

version: '3.3'
networks: 
  net_content:
services:
  content-database:
    image: content-database:latest
    build:
      context: .
      dockerfile: ./database/Dockerfile 
    networks: 
    - net_content
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: root
  content-redis:
    image: content-redis:latest
    build:
      context: .
      dockerfile: ./redis/Dockerfile 
    networks: 
    - net_content
  content-app:
    image: content-app:latest
    build:
      context: .
      dockerfile: ./content/Dockerfile 
    networks: 
      - net_content
    depends_on:
    - "content-database"

Any hint please?
Thanks!

Answer 1

您必须在./database/Dockerfile的Dockerfile中./database/Dockerfile内容数据库正在侦听的./database/Dockerfile

Answer 2

I guess MariaDB is listening on default port 3307 , this means your application has to connect to this port as well. I guess this is the case as you are mapping the port 3307 of your container to "the outside".

Change the port in your connection string:

url: jdbc:mariadb://content-database:3307/contentdb?autoReconnect=true