BACLIN.md

BACLIN - BAsic Compose LINeariser

This utility will linearise a file in the Docker Compose format so that all occurrences of extends directives are recursively replaced by the service definitions that they point at. It has been writter to circumvent issue #31101, i.e. to palliate the removal of extends directive between version 2 and version 3 of the compose file format.

Using this tool, you should be able to write extends directives in your compose 3 files, and linearise them before sending to the swarm using docker stack deploy. Obviously, these files would not comply to version 3+ of the file format specification as it lacks support for extend.

The tool takes two arguments on the command line: the path to the input file and the path to the output file. Each argument can be replaced by a -, meaning reading from standard in or writing to standard out. Empty (or missing) arguments will have the same meaning as the use of the more explicit dash. When reading from the standard input, baclin will default to the current directory as the root for relative file specifications that could happen in extends directives.

Example

Provided a main compose file with the following content:

version: 3

services:
    web:
      extends:
        file: ../common.yml
        service: webapp
      environment:
        - DEBUG=1
      cpu_shares: 5

    important_web:
      extends: web
      cpu_shares: 10

And the file at ../common.yml containing:

version: 2

services:
    common:
        labels:
            se.sics.copyright: "Emmanuel Frecon"
            se.sics.organisation: "RISE SICS"
    webapp:
        extends: common
        labels:
            se.sics.application: "Web"
        image: nginx
        ports:
          - "8000:8000"
        volumes:
          - "/data"
        environment:
            - TEST=34

Running baclin on the main file would lead to the following content:

version: "3"
services:
  web:
    labels:
      se.sics.copyright: Emmanuel Frecon
      se.sics.organisation: RISE SICS
      se.sics.application: Web
    image: nginx
    ports:
      - 8000:8000
    volumes:
      - /data
    environment:
      - TEST=34
      - DEBUG=1
    cpu_shares: 5
  important_web:
    labels:
      se.sics.copyright: Emmanuel Frecon
      se.sics.organisation: RISE SICS
      se.sics.application: Web
    image: nginx
    ports:
      - 8000:8000
    volumes:
      - /data
    environment:
      - TEST=34
      - DEBUG=1
    cpu_shares: 10

Binaries

Binaries, automatically generated using make.tcl ar available here.