Is it possible to have build-only service?

[rivaros]

Suppose I have the following config (simplified):

  src:
    build:
      context: deploy/src
    image: myname/base

  fpm:
    build:
      context: deploy/fpm
    image: myname/fpm

Dockerfile for fpm is located in deploy/fpm, Dockerfile for src is located in deploy/src
Dockerfile for myname/fpm image extends from myname/base image

FROM myname/base

Therefore I need to include both services (src & fpm), and make containers from them.
Is it possible to specify that src service is for build only.
So it first builds myname/base image and then myname/fpm image.

If I omit src it will not be able to find myname/base image since it was not build yet.

[shin-]

See my answer to a similar question in #4489

[rivaros]

@shin- thank you but it's more like "we don't support it/was not designed to do that etc". running 2 commands - this is obvious, but not nice. Have you tried any other tools like dobi?

[shin-]

I have used dobi. It's a great tool, written by @dnephin who has been a Compose maintainer for a while, so I highly recommend trying it out.

[n0099]

With

services:
  test-build-only:
    build:
      dockerfile_inline: |
        FROM scratch
    # choose one flavor between two entrypoints below
    entrypoint: sh -c exit
    entrypoint: 'true'
  some-service-build-on-test:
    build:
      args:
        COMPOSE_PROJECT_NAME: $COMPOSE_PROJECT_NAME

and in the Dockerfile of service some-service-build-on-test

FROM ${COMPOSE_PROJECT_NAME}-test-build-only

the image of services some-service-build-on-test will be build on test-build-only.

That two flavor of entrypoints only differences in running a shell sh -c with string exit to eval, or a process /bin/true to exit with code 0 that prevents docker container or compose restarting it with configured restart policy.

Make sure to build the image of service test-build-only before service some-service-build-on-test that its Dockerfile of image is based on test-build-only like manually determine the order by

docker compose build test-build-only && docker compose build

as currently there's no way to set the building order of uncached images in compose.yaml even with depends_on: #5228 (comment)

Note if you are not using services.build.dockerfile_inline, you will have to pass the compose env var $COMPOSE_PROJECT_NAME into Dockerfile via:

services:
  some-service-build-on-test:
    build:
      args:
        COMPOSE_PROJECT_NAME: $COMPOSE_PROJECT_NAME

ARG COMPOSE_PROJECT_NAME
FROM ${COMPOSE_PROJECT_NAME}-test-build-only

---

For your case in 8 years ago:

services:
  src:
    build:
      context: deploy/src
    image: myname/base
+    entrypoint: sh -c exit
+    entrypoint: 'true'

  fpm:
    build:
      context: deploy/fpm
      args:
        COMPOSE_PROJECT_NAME: $COMPOSE_PROJECT_NAME
    image: myname/fpm

and replace the FROM src in the dockerfile of service fpm with

ARG COMPOSE_PROJECT_NAME
FROM ${COMPOSE_PROJECT_NAME}-src

finally:

docker compose build src && docker compose build

[n0099]

And if you are using build-only service to achieve extending Dockerfile, also try build.additional_contexts.

[n0099]

  some-service-build-on-test:
    build:
      args:
        COMPOSE_PROJECT_NAME: $COMPOSE_PROJECT_NAME

and

ARG COMPOSE_PROJECT_NAME
FROM ${COMPOSE_PROJECT_NAME}-test-build-only

can be simplified with services.*.build.dockerfile_inline:

  some-service-build-on-test:
    build:
      dockerfile_inline:
        # syntax=docker/dockerfile:1
        FROM ${COMPOSE_PROJECT_NAME}-test-build-only
    depends_on:
      - test-build-only

And with

  some-service-build-on-test:
    image: ${COMPOSE_PROJECT_NAME}-test-build-only

the depends_on won't affect the building order, but the above dockerfile form will.