[Caching] Make ActionCache update failure non-fatal temporarily

[cachemeifyoucan]

Temporarily make action cache update non-fatal and not failing the job. The action cache update failure can happen due to cache poisoning from non-deterministic compiler output. Assume the errors from the non-determinism is benign and can be ignored till all issues are resolved.

rdar://146780363

[cachemeifyoucan]

@swift-ci please smoke test

[cachemeifyoucan]

ping

[benlangmuir]

The change LGTM, but would like a swift person to confirm use of errs() here is acceptable.

[cachemeifyoucan]

@artemcm @tshortli Throwing an error message that can't be sent to DiagnosticsEngine to stderr is fine to your eyes? It is unfortunately that we can't surface this properly but this should be a really rare error that user can't really fix.

[tshortli]

@artemcm @tshortli Throwing an error message that can't be sent to DiagnosticsEngine to stderr is fine to your eyes? It is unfortunately that we can't surface this properly but this should be a really rare error that user can't really fix.

Seems ok to me!

[cachemeifyoucan]

@swift-ci please smoke test

[akyrtzi]

How does this interact with the mechanism to run the compile twice and fail the build if there are non-determinism issues, will this change prevent that mechanism from working?

[cachemeifyoucan]

How does this interact with the mechanism to run the compile twice and fail the build if there are non-determinism issues, will this change prevent that mechanism from working?

The swift deterministic check actually doesn't use caching. Maybe I should introduce a new version that checks from caching so there are no false positives from files changing on disk.

[akyrtzi]

Would it be useful to have a way to bring back the error instead of ignoring, maybe via an environment variable?

[cachemeifyoucan]

Would it be useful to have a way to bring back the error instead of ignoring, maybe via an environment variable?

Not currently. I don't see using this error message for deterministic output check at all.

[cachemeifyoucan]

@swift-ci please test windows platform

[akyrtzi]

Would it be useful to have a way to bring back the error instead of ignoring, maybe via an environment variable?

Not currently. I don't see using this error message for deterministic output check at all.

We may not have a direct use right now, but it's simple to add for future-proofing. E.g. possibly in the future we take care of the non-determinism issues and we want to try making it back to an error for some internal CI.

[cachemeifyoucan]

@swift-ci please smoke test