CacheBeta@1 cannot find directory that definitely exists

Required Information

Type: Bug Task Name: CacheBeta@1

Environment

Server: Azure Pipelines Agent: Hosted

Issue Description

I had a cache task set up as following:

- task: CacheBeta@1
  displayName: Define build dependencies cache
  inputs:
    key: '"v1" | "build-deps" | $(CI_WORKSPACE_DIRECTORY)/cache/tools-perl-version | $(CI_WORKSPACE_DIRECTORY)/cache/build-deps-cpanfile'
    path: /usr/local/perl5/perlbrew/perls/tools-perl/lib/site_perl

The path definitely exists on disk.

However, I got an error when the job tried to save the cache contents.

Task logs

Attached

Error logs

tar: /usr/local/perl5/perlbrew/perls/tools-perl/lib/site_perl: Cannot open: No such file or directory

logs_50.zip

[autarch]

Posted at https://developercommunity.visualstudio.com/idea/809838/make-docker-startup-faster.html

Thanks.

[johnterickson]

Good feedback on docs, @autarch! Higher level question - if there were good layer caching, would you use that instead?

@vtbassmatt for:

Also, in general, the docs could do more to explain the host/container relationship and how that affects various types of steps. In particular, I think it would be good advice to tell people to only use mounted volumes when writing to disk, as that makes it a lot simpler to map them between host & container using the various pre-defined variables.