Cache Not Restored if Created on Base Branch

[daniel-nagy]

Given the following branches,

main -> base-1 -> base-2

Caches created on base-1 cannot be restored on base-2. However, according to the documentation it sounds like this should work.

A workflow can access and restore a cache created in the current branch, the base branch (including base branches of forked repositories), or the default branch (usually main)

This is enough to reproduce.

name: GH Actions Test
on:
  pull_request:
  push:
    branches:
      - main
jobs:
  test:
    env:
      BASE_SHA: ${{ github.event_name == 'pull_request' && github.event.pull_request.base.sha || '' }}
      HEAD_SHA: ${{ github.event_name == 'pull_request' && github.event.pull_request.head.sha || github.sha }}
    runs-on: ubuntu-latest
    steps:
      - name: try to restore cache from base branch
        if: github.event_name == 'pull_request'
        id: restore-cache
        uses: actions/cache@v3
        with:
          path: ${{ env.BASE_SHA }}
          key: ${{ runner.os }}-${{ env.BASE_SHA }}
      - name: cache
        uses: actions/cache@v3
        with:
          path: ${{ env.HEAD_SHA }}
          key: ${{ runner.os }}-${{ env.HEAD_SHA }}
      - name: debug
        run: echo ${{ steps.restore-cache.outputs.cache-hit }}
      - name: create file
        run: |
          mkdir $HEAD_SHA 2>/dev/null && echo 'foo' > "$HEAD_SHA/foo.txt"

base-1 is able to restore the cache create by main but base-2 is not able to restore the cache created by base-1.

[guppy0356]

Hello @daniel-nagy . I faced the same problem. I think this comment is the answer.

link: https://github.com/actions/cache/issues/843#issuecomment-1179771256

[vsvipul]

This will require a docs change. We are going to update it. Thank you for reporting. #877 and #843 also have the same issue. I've closed those and using this issue for tracking.

[Logarithmus]

@vsvipul are there any big technical challenges about enabling cache restore from base branch, not only default? At my workplace we use release/... branches and merge PRs into them instead of main, thus every time a new PR is created, the cache is not found.

I feel like changing the documentation isn't really a solution, but a workaround)

[Phantsure]

@Logarithmus There is some technical challenge in understanding the base branch for any branch so for now we have updated the docs to address this behaviour.

[Phantsure]

Closing this issue as public docs are updated: https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache @Logarithmus You may open a new issue with the expected behaviour. We can track that separately