CNB lifecycle can't restore cached layer for go-mod

[bstick12]

What version of Cloud Foundry and CF CLI are you using? (i.e. What is the output of running cf curl /v2/info && cf version?
N/A - Was testing the go-mod using kpack

What version of the buildpack you are using?
[email protected]

If you were attempting to accomplish a task, what was it you were attempting to do?
Rebuild an image using kpack where caching was enabled

What did you expect to happen?
The image would be re-built using the cached layers

What was the actual behavior?
The lifecycle of CNB fails at restore as the layer tar can be uncompressed

Restoring cached layer 'org.cloudfoundry.go-mod:go-mod'
Error: failed to restore: mkdir /layers/org.cloudfoundry.go-mod/go-mod/pkg/mod/github.com/bstick12/[email protected]/.circleci: permission denied

The previous layer is correctly used from cache

Restoring cached layer 'org.cloudfoundry.go-compiler:ac2a6efcc1f5ec8bdc0db0a988bb1d301d64b6d61b7e8d9e42f662fbb75a2b9b'
Restoring cached layer 'org.cloudfoundry.go-compiler:go'

The problem lies with the go module package paths. The package directories are not writeable. Apparently this is by design as discussed in golang/go#27161 and golang/go#27455 (comment)

  File: /layers/org.cloudfoundry.go-mod/go-mod/pkg/mod/github.com/bstick12/[email protected]/
  Size: 4096      	Blocks: 8          IO Block: 4096   directory
Device: 6ch/108d	Inode: 300555      Links: 4
Access: (0500/dr-x------)  Uid: ( 1000/     cnb)   Gid: ( 1000/     cnb)

This permission is preserved in the tarball

dr-x------ 1000/1000         0 1980-01-01 00:00 /layers/org.cloudfoundry.go-mod/go-mod/pkg/mod/github.com/bstick12/[email protected]
d

Since without a change to the tar or untaring process for this buildpack the caching process will break. Would be possible to disable caching.

Can you provide a sample app?

The behaviour should be the same for any go application that use go modules.

Please confirm where necessary:

• I have included a log output
• My log includes an error message
• I have included steps for reproduction

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/168351842

The labels on this github issue will be updated when the story is started.

[sclevine]

Hi @bstick12,

This appears to be an issue with the CNB lifecycle. It should be possible to restore layers regardless of their permissions. The lifecycle should implement the equivalent of tar --delay-directory-restore -x....

Would you mind opening an issue here?
https://github.com/buildpack/lifecycle

[bstick12]

Thanks @sclevine. I've opened buildpacks/lifecycle#177

[thitch97]

@bstick12 Closing this issue in favor of buildpack/lifecycle#177.