Simpler docker-compose with inline config files

So you have some config that you want to provide to a service started from docker compose.

Did you know you can keep things simple by inlining that config in the compose file, rather than messing with mounts?

Inline content in docker-compose.yaml

In our case we want a json file with 👇 mounted at /etc/consul/client.json

{
  "node_name": "consul-client",
  "data_dir": "/consul/data",
  "log_level": "ERROR",
  "server": false,
  "retry_interval": "10s",
  "retry_join":[
      "consul-server"
  ]
}

You can create a config section in your docker-compose.yaml file and provide the content of the file.

configs:
  consul_client.json:
    content: |
      {
          "node_name": "consul-client",
          "data_dir": "/consul/data",
          "log_level": "ERROR",
          "server": false,
          "retry_interval": "10s",
          "retry_join":[
              "consul-server"
          ]
      }

This works by creating an entry for the file and use the | sign on the content field to inline the content of the file. | accepts a multiline string and preserves new lines /n in the output.

Then we can add a configs section under the service, where we want to mount the file, specifying the source as the name we used 👆 consule_client.json and target as the path on disk where the file should be placed in the container /etc/consul/client.json.

    configs:
      - source: consul_client.json
        target: /etc/consul/client.json

All together this looks like 👇

configs:
  consul_client.json:
    content: |
      {
          "node_name": "consul-client",
          "data_dir": "/consul/data",
          "log_level": "ERROR",
          "server": false,
          "retry_interval": "10s",
          "retry_join":[
              "consul-server"
          ]
      }      
services:
  windmill-host:
    build:
      context: .
      dockerfile: ./mock-services/some-host/Dockerfile
    container_name: windmill-host
    ...
    configs:
      - source: consul_client.json
        target: /etc/consul/client.json

Docs

Here are the Docker docks which go into more detail:

Mini Series

This is part of a set of posts on useful Advanced Docker techniques