无法连接到mysql docker镜像连接被拒绝

Question

I just replaced my old company computer for a new one(MACOS), download the projects and now Im trying to connect to mysql docker image but I always get

dial tcp 127.0.0.1:3306: connect: connection refused

In my old computer everything worked correctly but now I've this problem.

My docker compose(Not showing all the content):

version: "3"
services:
  mysql:
    image: mysql:5.6
    ports:
      - "3306:3306"
    volumes:
      - mysql-data:/var/lib/mysql
      - ./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: a
      LANG: C.UTF-8
  adminer:
    image: adminer
    ports:
      - 8082:8080
  nginx:
    build: ../docker-shared/nginx
    ports:
      - 443:443
    volumes:
      - "./nginx_proxy_settings.conf:/etc/nginx/conf.d/nginx_proxy_settings.conf"
volumes:
  mysql-data:

So if I do a docker-compose up everything works, you can check in the next image the Adminer is working with data:

This is my Golang code to connect to mysql:

func main() {

    dbConfig := mysql.NewConfig()
    dbConfig.User = "root"
    dbConfig.Passwd = "a"
    dbConfig.Addr = "mysql"
    dbConfig.DBName = "company_prod"

    db, err := sql.Open("mysql", dbConfig.FormatDSN())
    if err != nil {
        panic(err)
    }
    defer db.Close()
}

Do you know what Im doing wrong??

Thank you

Answer 1

The problem is that your go code can't resolve the mysql address, as it's not being deployed in the compose file.

To fix that, you have two solutions:

1. Add your app to your docker-compose file by Dockerizing your code if it isn't already done, then it should be able to connect to your mysql container.
2. Expose your mysql container's ports and change the address used in your go code from mysql to localhost:3306 (I see that you edited your compose and the ports are exposed, so you just need to change the address in your code)

For the first solution, you can build a simple Go app into a Docker image like this:

# Build stage
FROM golang:alpine AS build-env

COPY . /go/src/your/project/path
WORKDIR /go/src/your/project/path

RUN apk update && \
    apk upgrade && \
    <install your deps here if needed>

# Install dep if needed
ENV DEP_VERSION="0.4.1"
RUN curl -L -s https://github.com/golang/dep/releases/download/v${DEP_VERSION}/dep-linux-amd64 -o $GOPATH/bin/dep
RUN chmod +x $GOPATH/bin/dep
RUN dep ensure

# Build your app
RUN go build -o myapp

# Final stage
FROM alpine

WORKDIR /app/myapp
COPY --from=build-env /go/src/your/project/path /app/myapp
ENTRYPOINT ["/app/myapp/myapp"]

Then add it to your compose file:

version: "3"
services:
  mysql:
    image: mysql:5.6
    ports:
      - "3306:3306"
    volumes:
      - mysql-data:/var/lib/mysql
      - ./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d
    environment:
      MYSQL_ROOT_PASSWORD: a
      LANG: C.UTF-8
  adminer:
    image: adminer
    ports:
      - 8082:8080
  myapp:
    build: .
    depends_on:
      - mysql
  nginx:
    build: ../docker-shared/nginx
    ports:
      - 443:443
    volumes:
      - "./nginx_proxy_settings.conf:/etc/nginx/conf.d/nginx_proxy_settings.conf"
volumes:
  mysql-data:

And add the port and the transport to your app's code:

func main() {

    dbConfig := mysql.NewConfig()
    dbConfig.User = "root"
    dbConfig.Passwd = "a"
    dbConfig.Addr = "mysql:3306"
    dbConfig.DBName = "websays_prod"
    dbConfig.Net = "tcp"

    db, err := sql.Open("mysql", dbConfig.FormatDSN())
    if err != nil {
        panic(err)
    }
    defer db.Close()
}

Second solution if you don't want to dockerize your app is to just change your code to:

func main() {

    dbConfig := mysql.NewConfig()
    dbConfig.User = "root"
    dbConfig.Passwd = "a"
    dbConfig.Addr = "localhost:3306"
    dbConfig.DBName = "websays_prod"
    dbConfig.Net = "tcp"

    db, err := sql.Open("mysql", dbConfig.FormatDSN())
    if err != nil {
        panic(err)
    }
    defer db.Close()
}