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38 lines
3.1 KiB
Markdown
38 lines
3.1 KiB
Markdown
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#### Cache segment restore timeout
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A cache gets downloaded in multiple segments of fixed sizes (`1GB` for a `32-bit` runner and `2GB` for a `64-bit` runner). Sometimes, a segment download gets stuck which causes the workflow job to be stuck forever and fail. Version `v3.0.8` of `actions/cache` introduces a segment download timeout. The segment download timeout will allow the segment download to get aborted and hence allow the job to proceed with a cache miss.
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Default value of this timeout is 60 minutes and can be customized by specifying an [environment variable](https://docs.github.com/en/actions/learn-github-actions/environment-variables) named `SEGMENT_DOWNLOAD_TIMEOUT_MINS` with timeout value in minutes.
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#### Update a cache
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A cache today is immutable and cannot be updated. But some use cases require the cache to be saved even though there was a "hit" during restore. To do so, use a `key` which is unique for every run and use `restore-keys` to restore the nearest cache. For example:
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```yaml
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- name: update cache on every commit
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uses: actions/cache@v3
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with:
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path: prime-numbers
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key: primes-${{ runner.os }}-${{ github.run_id }} # Can use time based key as well
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restore-keys: |
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primes-${{ runner.os }}
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```
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Please note that this will create a new cache on every run and hence will consume the cache [quota](#cache-limits).
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#### Use cache across feature branches
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Reusing cache across feature branches is not allowed today to provide cache [isolation](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache). However if both feature branches are from the default branch, a good way to achieve this is to ensure that the default branch has a cache. This cache will then be consumable by both feature branches.
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#### Improving cache restore performance on Windows/Using cross-os caching
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Currently, cache restore is slow on Windows due to tar being inherently slow and the compression algorithm `gzip` in use. `zstd` is the default algorithm in use on linux and macos. It was disabled on Windows due to issues with bsd tar(libarchive), the tar implementation in use on Windows.
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To improve cache restore performance, we can re-enable `zstd` as the compression algorithm using the following workaround. Add the following step to your workflow before the cache step:
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```yaml
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- if: ${{ runner.os == 'Windows' }}
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name: Use GNU tar
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shell: cmd
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run: |
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echo "Adding GNU tar to PATH"
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echo C:\Program Files\Git\usr\bin>>"%GITHUB_PATH%"
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```
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The `cache` action will use GNU tar instead of bsd tar on Windows. This should work on all Github Hosted runners as it is. For self-hosted runners, please ensure you have GNU tar and `zstd` installed.
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The above workaround is also needed if you wish to use cross-os caching since difference of compression algorithms will result in different cache versions for the same cache key. So the above workaround will ensure `zstd` is used for caching on all platforms thus resulting in the same cache version for the same cache key.
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