Docker Compose inline configuration file

You know I am the big fan of docker compose (fig 😸). I am the advanced user in compose and swarm. Deployed swarm based cluster for different product and its handles millions of request every day.

The requirement

Here is the example about how we can use a single YAML file for docker services and configuration. We don’t need separate file or folder maintained in the repo. Just single docker-compose.yml file is enough. All the configuration is with in that as inline content.

Lets dive into the topic.

We want to deploy a nginx proxy.
Its has a configuration file.
It has HTML file to serve.
It has a image file to serve.

Single YAML

How I can define the inline config file

configs:
  nginx.conf:
    content: |
      your config file content

Refer this doc in GitHub.

Here is the compose yaml file for nginx serve the html file content.

name: nginx-inline
services:
  nginx:
    image: nginx:1.27.1
    ports:
      - 8080:80
    configs:
      - source: index.html
        target: /usr/share/nginx/html/index.html
configs:
  index.html:
    content: |
      <!doctype html>
      <html>
        <head>
          <title>Hello nginx</title>
          <meta charset="utf-8" />
        </head>
        <body>
          <h1>
            Hello arulraj.net!
          </h1>
        </body>
      </html>

Bring up the system using docker-compose up -d. Then access http://localhost:8080

Now you see the page like this.

The index.html loaded successfully.

Environmental interpolation

You can do the environmental interpolation in docker-compose.yml file in a usual way.

The good old .env file
OR use export before ran docker-compose up -d

The following content has WELCOME_MESSAGE in the index.html

configs:
  index.html:
    content: |
      <!doctype html>
      <html>
        <head>
          <title>Hello nginx</title>
          <meta charset="utf-8" />
        </head>
        <body>
          <h1>
            ${WELCOME_MESSAGE:-Hello, World!}
          </h1>
        </body>
      </html>

Then

export WELCOME_MESSAGE="Hello, Arul!"
docker-compose up -d

Store environmental variable as config file

Expose the host machine environment variable inside the container as config file.

name: nginx-inline
services:
  nginx:
    image: nginx:1.21.1
    ports:
      - 8080:80
    configs:
      - source: path.txt
        target: /usr/share/nginx/html/path.txt
configs:
  path.txt:
    environment: "PATH"

Here we expose the host machine PATH env as path.txt

Binary file

The binary file converted as base64 and can be used.

But this is not supported in compose spec as like kubernetes.

Will update this post once its supported.