CODEWITHSUNDEEP
dockerdocker-compose
basickarl
basickarl

Reputation: 40444

Service access another service on 127.0.0.1?

I'd like my web Docker container to access Redis on 127.0.0.1:6379 from within the web container. I've setup my Docker Compose file as the following. I get ECONNREFUSED though:

version: "3"

services:
  web:
    build: .
    ports:
      - 8080:8080
    command: ["test"]
    links:
      - redis:127.0.0.1
  redis:
    image: redis:alpine
    ports: 
      - 6379

Any ideas?

Upvotes: 5

Views: 1500

Answers (1)

BMitch
BMitch

Reputation: 263469

The short answer to this is "don't". Docker containers each get their own loopback interface, 127.0.0.1, that is separate from the host loopback and from that of other containers. You can't redefine 127.0.0.1, and if you could, that would almost certainly break other things.

There is a technically possible way to do it by either running all containers directly on the host, with:

network_mode: "host"

However, that removes the docker network isolation that you'll want with containers.

You can also attach one container to the network of another container (so they have the same loopback interface) with:

docker run --net container:$container_id ...

but I'm not sure if there's a syntax to do this in docker-compose and it's not available in swarm mode since containers may run on different nodes. The main use I've had for this syntax is attach network debugging tools like nicolaka/netshoot.

What you should do instead is make the location of the redis database a configuration parameter to your webapp container. Pass the location in as an environment variable, config file, or command line parameter. If the web app can't support this directly, update the configuration with an entrypoint script that runs before you start your web app. This would change your compose yml file to look like:

version: "3"

services:
  web:
    # you should include an image name
    image: your_webapp_image_name
    build: .
    ports:
      - 8080:8080
    command: ["test"]
    environment:
      - REDIS_URL=redis:6379

    # no need to link, it's deprecated, use dns and the network docker creates
    #links:
    #  - redis:127.0.0.1
  redis:
    image: redis:alpine
    # no need to publish the port if you don't need external access
    #ports: 
    #  - 6379

Upvotes: 2

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