Added tips and workarounds for cross os

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Sampark Sharma 2022-12-27 11:00:08 +00:00 committed by GitHub
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@ -28,7 +28,6 @@ See ["Caching dependencies to speed up workflows"](https://docs.github.com/en/ac
* Fix zstd not working for windows on gnu tar in issues.
* Allowing users to provide a custom timeout as input for aborting download of a cache segment using an environment variable `SEGMENT_DOWNLOAD_TIMEOUT_MINS`. Default is 60 minutes.
* Two new actions available for granular control over caches - [restore](restore/action.yml) and [save](save/action.yml)
* Add support for cross os caching. For example, a cache saved on windows can be restored on ubuntu and vice versa.
Refer [here](https://github.com/actions/cache/blob/v2/README.md) for previous versions
@ -245,6 +244,7 @@ Following are some of the known practices/workarounds which community has used t
- [Cache segment restore timeout](./tips-and-workarounds.md#cache-segment-restore-timeout)
- [Update a cache](./tips-and-workarounds.md#update-a-cache)
- [Use cache across feature branches](./tips-and-workarounds.md#use-cache-across-feature-branches)
- [Improving cache restore performance on Windows/Using cross-os caching](./tips-and-workarounds.md#improving-cache-restore-performance-on-windows-using-cross-os-caching)
- [Force deletion of caches overriding default cache eviction policy](./tips-and-workarounds.md#force-deletion-of-caches-overriding-default-cache-eviction-policy)
#### Windows environment variables

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@ -59,4 +59,7 @@
### 3.2.1
- Update `@actions/cache` on windows to use gnu tar and zstd by default and fallback to bsdtar and zstd if gnu tar is not available. ([issue](https://github.com/actions/cache/issues/984))
- Added support for fallback to gzip to restore old caches on windows.
- Added logs for cache version in case of a cache miss.
- Added logs for cache version in case of a cache miss.
### 3.2.2
- Reverted the changes made in 3.2.1 to use gnu tar and zstd by default on windows.

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@ -19,6 +19,24 @@ A cache today is immutable and cannot be updated. But some use cases require the
## Use cache across feature branches
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.
## Improving cache restore performance on Windows/Using cross-os caching
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.
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:
```yaml
- if: ${{ runner.os == 'Windows' }}
name: Use GNU tar
shell: cmd
run: |
echo "Adding GNU tar to PATH"
echo C:\Program Files\Git\usr\bin>>"%GITHUB_PATH%"
```
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.
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.
## Force deletion of caches overriding default cache eviction policy
Caches have [branch scope restriction](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache) in place. This means that if caches for a specific branch are using a lot of storage quota, it may result into more frequently used caches from `default` branch getting thrashed. For example, if there are many pull requests happening on a repo and are creating caches, these cannot be used in default branch scope but will still occupy a lot of space till they get cleaned up by [eviction policy](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#usage-limits-and-eviction-policy). But sometime we want to clean them up on a faster cadence so as to ensure default branch is not thrashing. In order to achieve this, [gh-actions-cache cli](https://github.com/actions/gh-actions-cache/) can be used to delete caches for specific branches.