Docker : Re-use container image by caching - docker

Question

Here I have two workflows under a job. The only target we want to achieve is that, we want to reuse the container images by using cache or some other means. Similar way we do for node_modules
jobs:
build:
name: build
runs-on: [self-hosted, x64, linux, research]
container:
image: <sample docker image>
env:
NPM_AUTH_TOKEN: <sample token>
steps:
- uses: actions/checkout#v2
- name: Install
run: |
npm install
- name: Build
run: |
npm build
Test:
name: Test Lint
runs-on: [self-hosted, x64, linux, research]
container:
image: <sample docker image>
env:
NPM_AUTH_TOKEN: <sample token>
steps:
- uses: actions/checkout#v2
- name: Install Dependencies
run: npm ci
- name: Lint Check
run: npm run lint

Answer 1

I would suggest using the Docker's Build Push action for this purpose. Through the build-push-action, you can cache your container images by using the inline cache, registry cache or the experimental cache backend API:
Inline cache
name: Build and push
uses: docker/build-push-action#v2
with:
context: .
push: true
tags: user/app:latest
cache-from: type=registry,ref=user/app:latest
cache-to: type=inline
Refer to the Buildkit docs.
Registry Cache
name: Build and push
uses: docker/build-push-action#v2
with:
context: .
push: true
tags: user/app:latest
cache-from: type=registry,ref=user/app:buildcache
cache-to: type=registry,ref=user/app:buildcache,mode=max
Refer to Buildkit docs.
Cache backend API
name: Build and push
uses: docker/build-push-action#v2
with:
context: .
push: true
tags: user/app:latest
cache-from: type=gha
cache-to: type=gha,mode=max
Refer to Buildkit docs.
I personally prefer using the Cache backend API as its easy to setup and provides a great boost in reducing the overall CI pipeline run duration.
By looking at the comments, it seems you want to share Docker cache between workflows. In this case you can share Docker containers between jobs in a workflow using this example:
jobs:
build:
runs-on: ubuntu-latest
steps:
-
name: Checkout
uses: actions/checkout#v2
-
name: Set up Docker Buildx
uses: docker/setup-buildx-action#v1
-
name: Build and push
uses: docker/build-push-action#v2
with:
context: .
file: ./Dockerfile
tags: myimage:latest
outputs: type=docker,dest=/tmp/myimage.tar
-
name: Upload artifact
uses: actions/upload-artifact#v2
with:
name: myimage
path: /tmp/myimage.tar
use:
runs-on: ubuntu-latest
needs: build
steps:
-
name: Set up Docker Buildx
uses: docker/setup-buildx-action#v1
-
name: Download artifact
uses: actions/download-artifact#v2
with:
name: myimage
path: /tmp
-
name: Load Docker image
run: |
docker load --input /tmp/myimage.tar
docker image ls -a

Answer 2

In general, data is not shared between jobs in GitHub Actions (GHA). jobs actually will run in parallel on distinct ephemeral VMs unless you explicitly create a dependency with needs
GHA does provide a cache mechanism. For package manager type caching, they simplified it, see here.
For docker images, you either can use docker buildx cache and cache to a remote registry (including ghcr), or use the GHA cache action, which probably is easier. The syntax for actions/cache is pretty straightforward and clear on the page. For buildx, documentation always has been a bit of an issue (largely, I think, because he people building it are so smart that they do not realize how much we do not understand what is in their hearts), so you would need to configure the cache action, and then buildx to cache it.
Alternatively, you could do docker save imagename > imagename.tar and use that in the cache. There is a decent example of that here. No idea who wrote it, but it does the job.