Spring boot app can't connect to MySQL database in docker

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1

Hi!

Im fairly new to docker, and today i run into this issue. I have a spring boot app, an angular frontend and a MySQL database, which works fine in my local environment. The spring boot app can connect to the database, i see it in MySQL Workbench.

I tried to dockerise this app, and it seems that my spring app can’t connect to the database in the docker container.

Here is my compose file:

services:
  mysql:
    image: mysql:8.0
    container_name: mysql
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: moa_db
    ports:
      - "3307:3306"
    volumes:
      - mysql_data:/var/lib/mysql
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "mysql", "--silent"]
      interval: 10s
      retries: 5
      start_period: 30s
      timeout: 5s
    restart: unless-stopped
    networks:
      - mynetwork

  backend:
    build:
      context: ./backend
      dockerfile: dockerfile
    container_name: spring-boot-app
    ports:
      - "8080:8080"
    environment:
      SPRING_DATASOURCE_URL: jdbc:mysql://mysql:3306/moa_db?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&useSSL=false&createDatabaseIfNotExist=true
      SPRING_DATASOURCE_USERNAME: root
      SPRING_DATASOURCE_PASSWORD: root
    depends_on:
      mysql:
        condition: service_healthy
    restart: on-failure
    networks:
      - mynetwork

  frontend:
    build:
      context: ./frontend
      dockerfile: dockerfile
    container_name: angular-app
    ports:
      - "4200:80"
    depends_on:
      - backend
    networks:
      - mynetwork

volumes:
  mysql_data:
  
networks:
  mynetwork:
    driver: bridge

And here is my 2 dockerfile:
Backend:

FROM gradle:7.4.2-jdk11 AS builder
WORKDIR /app
COPY . .
RUN gradle build --no-daemon

FROM openjdk:11-jdk-slim
WORKDIR /app
COPY --from=builder /app/build/libs/moa-backend-0.0.1-SNAPSHOT.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

FrontEnd:

FROM node:14-alpine as build

WORKDIR /app

COPY package*.json ./
RUN npm install

COPY . .
RUN npm run build --prod

FROM nginx:alpine
COPY --from=build /app/dist/moa-frontend /usr/share/nginx/html

EXPOSE 80

I tried with creating a network bridge, but it didn’t help and i also read that docker now has a built in network.
A fun part is, i tried changing the connection url in the compose file to

SPRING_DATASOURCE_URL: jdbc:mysql://host.docker.internal:3306/moa_db?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true&useSSL=false&createDatabaseIfNotExist=true

And this resulted in a short success, if i had MySQL workbench open, it connected to it locally, but when i closed it, it also didn’t work.

I have the ports like this: “3307:3306” because it told me that locally i use 3306.

Any suggestions what am i doing wrong?
Thanks for the help in advance!

2

The container uses port 3306, but maps it to host port 3307

If you want to access it through another container, you don’t need to map the port, and can do so simply by using mysql://mysql:3306

To access it from the host port it’s mapped to, you’d need port 3307

3

What does that mean? Is there an error message? Is the database container up and running?

4

Sorry, i forgot the error from the post, I got this error:
java.sql.SQLNonTransientConnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.

5

By the way, i found another error:
com.mysql.cj.exceptions.UnableToConnectException: Public Key Retrieval is not allowed

After some googling, I think i solved my problem by adding &allowPublicKeyRetrieval=true to my connection url

now it seems to work fine