Question 20103 in Mysql Question posted in
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Communication Link Failure after Running MySQL and Spring Application in Docker

I’m trying to run my spring boot application on docker with mysql.
Everything is working fine, MySQL DB starts successfully and after that spring application is deployed in container and I end up getting this error :

Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure

This is my docker compose yaml file content:

version: "3.8"

services:
  mysql-db:
    image: mysql
    container_name: mysqldb
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: employeedb
      MYSQL_HOST: mysql-db
      MYSQL_PORT: 3306
    networks:
      - mt-network

networks:
  mt-network:
    driver: bridge

And my application-properties.yml file content:

spring:
 datasource:
  password: root
  url: jdbc:mysql://mysql-db:3306/employeedb
  username: root
  driver-class-name: com.mysql.cj.jdbc.Driver
 jpa:
  hibernate:
   ddl-auto: update

I tried all ways to fix this but I’m still facing this issue. Please don’t put this question as Duplicate Question.

Thank you in advance.

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    There was something wrong with mysql container I guess it was not starting properly.

    So I added HealthCheck in docker compose and now after i run docker-compose up the mysql container starts and after that it stops for few second. After few seconds my spring application starts working without giving me error : Communication Link Failure.

    EDIT:

    Usually whats happening is that until MySQL container is not in healthy state it will re-run it as many times which is given in docker-compose yaml file. And when the container is healthy it executes Spring Application container.

    Below is my docker-compose.yml file,

        version: "3.8"

services:
  spring-scon:
    container_name: scon
    build:
      context: ./
      dockerfile: Dockerfile
    ports:
      - 9090:8080
    depends_on: 
      mysqldb:
        condition: service_healthy
    networks:
      - spring-network
    restart: always

  mysqldb:
    image: mysql
    container_name: mysql

    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: employeedb
      MYSQL_HOST: mysqldb
      MYSQL_PORT: 3306

    ports:
      - "127.0.1.1:3306:3306"


    healthcheck:
      test: ["CMD-SHELL", 'mysqladmin ping']
      interval: 10s
      timeout: 2s
      retries: 10


    volumes:
      - dbdata:/usr/app

    networks:
     - spring-network

volumes:
  dbdata:
    external: true

networks:
  spring-network:
    driver: bridge

    Here, I don't know about IP "127.0.1.1" but I read somewhere we can configure port number with IP like I did in my docker-compose.yml. If someone knows what that IP means please explain it.

    I use that IP to connect Dockerized MySQL Server with my local MySQL Workbench.

    Thanks Once Again.


  2. 0

    First, remove the whole network configuration, it’s unnecessary:

    version: "3.8"

services:
  mysql-db:
    image: mysql
    container_name: mysqldb
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: employeedb
      MYSQL_HOST: mysql-db
      MYSQL_PORT: 3306

    You should use the container name mysqldb as hostname if your Spring Boot application is started with Docker Compose as well:

    spring:
 datasource:
  url: jdbc:mysql://mysqldb:3306/employeedb

    The documentation states:

    By default Compose sets up a single network for your app. Each container for a service joins the default network and is both reachable by other containers on that network, and discoverable by them at a hostname identical to the container name.

    If you start your Spring Boot app from your IDE, you need to use localhost as hostname because the app won’t be in the same network as the Docker container and won’t therefore not be able to resolve the hostname mysqldb:

    spring:
 datasource:
  url: jdbc:mysql://localhost:3306/employeedb
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