Store remote metadata in the on disk action cache

[buchgr]

This is part of #6862.

The persistent action cache stores the state of Bazel's output base. It does not know about remotely stored files. We need to extend it to do so.

$ bazel build :foo --experimental_remote_download_outputs=minimal
$ bazel shutdown
# This will be clean build, because the metadata from the previous build are
# not yet properly persisted to disk
$ bazel build :foo --experimental_remote_download_outputs=minimal

[moroten]

This problem makes up to several minutes for me. Any updates on priority?

[buchgr]

No updates.

[moroten]

I saw the related #10233 which talks about refactoring findMissingBlobs. Is there more difficulties relating to --experimental_inmemory_jdeps_files and --experimental_inmemory_dotd_files that needs to be considered? Would the right way to solve this issue be to implement --disk_cache support in combination with remote execution or should there be another flag involved?

I do see this phenomenon also when the analysis cache is discarded due to changing configuration flags, even if the server is still alive.

[coeuvre]

This can be enabled by setting --experimental_action_cache_store_output_metadata.