devcontainers
Inconsistent `pull_policy` behavior with `docker compose` when combining build and image
https://docs.docker.com/reference/compose-file/build/#using-build-and-image
https://docs.docker.com/reference/compose-file/services/#image
Using build and image When Compose is confronted with both a build subsection for a service and an image attribute, it follows the rules defined by the pull_policy attribute.
If pull_policy is missing from the service definition, Compose attempts to pull the image first and then builds from source if the image isn't found in the registry or platform cache.
i.e. by default it should pull image from registry/cache before attempting to build when using docker compose up, therefore I expect
.devcontainer/devcontainer.json --- JSON
1
2 {
3 "name": "Repro",
4 "dockerComposeFile": "../compose.yml",
5 "service": "devcontainer",
6 "workspaceFolder": ".",
7 "runServices": [
8 "db"
9 ]
10 }
11
compose.yml --- YAML
1 services:
2 devcontainer:
3 image: mcr.microsoft.com/devcontainers/base:ubuntu
4 volumes:
5 - ../..:/workspaces:cached
6 network_mode: service:db
7 command: sleep infinity
8
9 db:
10 image: postgres:latest
11 build:
12 context: .
13 dockerfile_inline: |
14 FROM postgres:latest
15 restart: unless-stopped
16 volumes:
17 - postgres-data:/var/lib/postgresql/data
18 environment:
19 POSTGRES_PASSWORD: postgres
20 POSTGRES_USER: postgres
21 POSTGRES_DB: postgres
22
23 volumes:
24 postgres-data:
25
(output from git diff)
to not run docker compose build db when running @devcontainers/cli up --workspace-folder .
But it currently runs docker compose --project-name devcontainer-repro -f <abbreviated-path>/devcontainer-repro/compose.yml build db devcontainer
Why this matters:
When trying to prebuild/cache images it is beneficial to have one compose.yml which both defines the image and how to build the image, otherwise you need to split the file in two compose.build.yml and compose.yml. This behavior is inconsistent and confusing.
