How to link two containers using docker-compose

问题

At the moment I have two containers which I build from an image and then link the two:

For example:

#mysql
docker build -t my/mysql docker-mysql
docker run -p 3306:3306 --name mysql -d my/mysql:latest

#webapp
docker build -t my/tomcat:7.0 tomcat/7.0
docker run -d --link mysql --name tomcat7 my/tomcat:7.0

Since I'm linking the webapp container with mysql container, the webapp container gets a MYSQL_PORT_3306_TCP_ADDR environment variable created. I use this environment variable to then connect to the mysql database in my jdbc string.

All of this works fine but now I'd like to use docker-compose so that everything can be built and ran from one command.

However, while playing with docker-compose I'm noticing that it prefixes docker_ to the image name and furthermore deprecates the link option.

Question

How would the above build/run commands translate to docker-compose yml file such that the webapp container can connect to the mysql container for jdbc.

回答1:

You need to add an alias attribute in the compose yml. The following is taken from the docs the docs and is a very short example

web:
  links:
   - db
   - db:database
   - redis

That compose snippet defines a web container which has to be linked to the db and redis containers and it also adds the db container with the alias `database.

In you case, I think the yml for the tomcat container would look something like this

mysql:
  image: my/mysql:latest
  ports:
  - "3306:3306"

tomcat7:
  image: my/tomcat:7.0
  links:
   - mysql

Bear in mind that the tomcat container is not exposing any ports!

回答2:

Here is a rough translation to a docker-compose.

Note that docker-compose tags it's own images, so say you made a mysql image in a directory named test, then the container name would turn into test_mysql_1. The 1 is appended on the end because you can scale up multiple containers using docker-compose.

This file also assumes this file-structure

├── docker-mysql
│   └── Dockerfile
├── tomcat
│   └── 7.0
│       └── Dockerfile
└── docker-compose.yml

version: '2'
services:
    mysql:
        build:
            context: "./docker-mysql"
        hostname: mysql
        ports:
            - "3306:3306"
    webapp:
        build:
            context: "./tomcat/7.0"
        hostname: tomcat7
        links:
            - mysql

来源：https://stackoverflow.com/questions/35729083/how-to-link-two-containers-using-docker-compose

标签

java

Docker

docker-compose