Connecting two docker containers

Question

I have two existing docker container web and db. I want to link these two container, so that they will communicate with each other. If i go with --link command means it will link web to a new image and not to the db.

score 43 · Accepted Answer · answered Aug 03 '17 at 12:15

43

Using --link was the only way of connecting containers before the advent of docker networks. These provide a "cleaner" solution to the problem of inter-container communication and at the same time solves 2 of the major limits of links:

restart of linked container breaks the link
links are not supported between containers running on different hosts

Using docker network you would use the --net option to start the containers on the specified network:

docker network create example
docker run -d --net example --name container1 <image>
docker run -d --net example --name container2 <image>

At this point the 2 container are mutually reachable via the address <container-name>.example: that is container1.example and container2.example.

answered Aug 03 '17 at 12:15

nivox

2,060
17
18

Thanks for your explanation. Now I got it. – Ragul Aug 04 '17 at 04:55
1

`--link` is deprecated now! I though really appreciate the example of --net. Will try it out. – aman_novice Aug 04 '17 at 14:12
Using --net it will come under a specific IP. But both the containers have different IPs like a Subnet IPs. Eg : Network IP is 180.12.10.0 means, container IP will be 180.12.10.1 and 180.12.10.2 respectively? – Ragul Aug 16 '17 at 10:43

score 5 · Answer 2 · edited Nov 22 '20 at 18:18

Just to benefit people that stumble upon this question. The --link feature is now considered legacy and is a prime candidate to be deprecated by docker. The easiest way is to use

depends_on:

In order to do this, its recommended to first create a network like so:

docker network create <network_name>

Then use docker-compose to spawn services that bind with each other. Look at the example below where I've bound my spring-boot app to rabbit-mq. You can clone my repo from here.

version: "3.1"
services:
  rabbitmq-container:
    image: rabbitmq:3.5.3-management
    hostname: rabbitmq-container
    ports:
      - 5673:5673
      - 5672:5672
      - 15672:15672
    networks:
      - resolute

  resolute-container:
    build: .
    ports:
      - 8080:8080
    environment:
      - spring_rabbitmq_host=rabbitmq-container
      - spring_rabbitmq_port=5672
      - spring_rabbitmq_username=guest
      - spring_rabbitmq_password=guest
      - resolute_rabbitmq_publishQueueName=resolute-run-request
      - resolute_rabbitmq_exchange=resolute
    depends_on:
      - rabbitmq-container
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    networks:
      - resolute

networks:
  resolute:
    external:
      name: resolute

See how I've created a network called resolute and bound the apps to the same network. I've also given my rabbitmq-container a hostname. This is because docker now prepends the container name and that makes it difficult to bind services by name.

Is there a limit of how many networks can exist on a docker host? — PHELMS, Dec 27 '20 at 06:57

score -2 · Answer 3 · answered Aug 03 '17 at 11:43

-2

link is used to connect containers so that they can communicate with each other once the communication is establish they will be able to communicate with your database.

answered Aug 03 '17 at 11:43

vegiops

293
2
6

I nearly discouraged this answer, while I normally never discourage answers. You schould provide more exemplary stuff, and the word link is nor a cli-option and nor do I know, where to use that option ... – Nikolai Ehrhardt Jan 23 '22 at 18:44
sure, thanks for the guidance will make sure I follow. – vegiops Jan 25 '22 at 04:47

Connecting two docker containers

3 Answers3

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