How to use a variable docker image in github-actions? - docker

Question

I am trying to write a custom github-action that runs some commands in a docker container but allows the user to select which docker container they are run in (i.e. so I can run the same build instructions across different versions of the runtime environment)
My gut instinct was to have my .github/actions/main/action.yml file as
name: 'Docker container command execution'
inputs:
dockerfile:
default: Dockerfile_r_latest
runs:
using: 'docker'
image: '${{ inputs.dockerfile }}'
args:
- /scripts/commands.sh
However this errors with:
##[error](Line: 7, Col: 10): Unrecognized named-value: 'inputs'. Located at position 1 within expression: inputs.dockerfile
Any help would be appreciated !
File References
My .github/workflow/build_and_test.yml file is:
name: Test Package
on:
[push, pull_request]
jobs:
R_latest:
name: Test on latest
runs-on: ubuntu-latest
steps:
- uses: actions/checkout#master
name: Checkout project
- uses: ./.github/actions/main
name: Build and test
with:
dockerfile: Dockerfile_r_latest
And my Dockerfile .github/actions/main/Dockerfile_r_latest is:
FROM rocker/verse:latest
ADD scripts /scripts
ENTRYPOINT [ "bash", "-c" ]

Answer 1

Interesting approach! I'm not sure if it's possible to use expressions in the image field of the action metadata. I would guess that the only fields that can take expressions instead of hardcoded strings are the args for the image so that the inputs can be passed.
For reference this is the args section of the action.yml metadata.
https://help.github.com/en/articles/metadata-syntax-for-github-actions#args
I think there are other ways to achieve what you want to do. Have you tried using the jobs.<job_id>.container syntax? That allows you to specify an image that the steps of a job will run in. It will require that you publish the image to a public repository, though. So take care not to include any secrets.
For example, if you published your image to Docker Hub at gowerc/r-latest your workflow might look something like this:
name: Test Package
on:
[push, pull_request]
jobs:
R_latest:
name: Test on latest
runs-on: ubuntu-latest
container: gowerc/r-latest
steps:
- uses: actions/checkout#master
name: Checkout project
- name: Build and test
run: ./scripts/commands.sh
ref: https://help.github.com/en/articles/workflow-syntax-for-github-actions#jobsjob_idcontainer
Alternatively, you can also specify your image at the step level with uses. You could then pass a command via args to execute your script.
name: my workflow
on: push
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout#master
- name: Check container
uses: docker://alpine:3.8
with:
args: /bin/sh -c "cat /etc/alpine-release"
ref: https://help.github.com/en/github/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#example-using-a-docker-hub-action

Answer 2

In addition to #peterevans answer, I would add there's a 3rd option where you can use a simple docker run command and pass any env that you have defined.
That helped to solve 3 things :
Reuse a custom docker image being build within the steps for testing actions. It seems not possible to do so with uses as it first tries to pull that image that doesn't exist yet in a Setup job step that occurs before any steps of the job.
This specific image can also be stored in a private docker registry
Be able to use a variable for the docker image
My workflow looks like this :
name: Build-Test-Push
on:
push:
branches:
- master
env:
AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
ECR_REGISTRY: ${{ secrets.AWS_ECR_REGISTRY }}
ECR_REPOSITORY: myproject/myimage
IMAGE_TAG: ${{ github.sha }}
jobs:
build-and-push:
runs-on: ubuntu-latest
steps:
- name: Checking out
uses: actions/checkout#v2
with:
ref: master
- name: Login to AWS ECR
id: login-ecr
uses: aws-actions/amazon-ecr-login#v1
- name: Build
run: |
docker pull $ECR_REGISTRY/$ECR_REPOSITORY || true
docker build . -t $ECR_REGISTRY/$ECR_REPOSITORY:$IMAGE_TAG -t $ECR_REGISTRY/$ECR_REPOSITORY:latest
- name: Test
run: |
docker run $ECR_REGISTRY/$ECR_REPOSITORY:latest /bin/bash -c "make test"
- name: Push
run: |
docker push $ECR_REGISTRY/$ECR_REPOSITORY

Answer 3

Here is another approach. The Docker image to use is passed to a cibuild shell script that takes care of pulling the right image.
GitHub workflow file:
name: 'GH Actions CI'
on:
push:
branches: ['*master', '*0.[0-9]?.x']
pull_request:
# The branches below must be a subset of the branches above
branches: ['*master', '*0.[0-9]?.x']
jobs:
build:
name: Build
runs-on: ubuntu-latest
strategy:
fail-fast: true
matrix:
include:
- FROM: 'ubuntu:focal'
- FROM: 'ubuntu:bionic'
- FROM: 'ubuntu:xenial'
- FROM: 'debian:buster'
- FROM: 'debian:stretch'
- FROM: 'opensuse/leap'
- FROM: 'fedora:33'
- FROM: 'fedora:32'
- FROM: 'centos:8'
steps:
- name: Checkout repository
uses: actions/checkout#v2
with:
# We must fetch at least the immediate parents so that if this is
# a pull request then we can checkout the head.
fetch-depth: 2
# If this run was triggered by a pull request event, then checkout
# the head of the pull request instead of the merge commit.
- run: git checkout HEAD^2
if: ${{ github.event_name == 'pull_request' }}
- name: Run CI
env:
FROM: ${{ matrix.FROM }}
run: script/cibuild
Bash script script/cibuild:
#!/bin/bash
set -e
docker run --name my-docker-container $FROM script/custom-script.sh
docker cp my-docker-container:/usr/src/my-workdir/my-outputs .
docker rm my-docker-container
echo "cibuild Done!"
Put your custom commands in script/custom-script.sh.