Running container_test in bazel can't be cached

[Monnoroch]

This tool outputs logs with records like this one:

time="2018-11-23T22:18:33Z" level=info msg="Extracting image tar to obtain image file system"

These records contain timestamps, therefore, logs have different hash on each execution and my remote-caching cas says there's no files for it's digest. Interestingly enough, local caching does work, although I don't really understand how.

container_test rule does pass --quiet to this binary, but that doesn't seem to work (or does something unrelated to logs).

Possibly related: #52.

[nkubala]

Hey @Monnoroch, thanks for the issue. Surprising to see that you're getting different results remotely vs. locally...do you know of any differences between how caching is done between the two in bazel?

If the rule is already passing --quiet to the binary and that doesn't fix it, then I'm not really sure what to do here. I don't think we're gonna take out the timestamp information from the logs. Maybe in the rule we could try and do some output redirection a la the issue you referenced here?

I'm not doing any work on the bazel rules side of this anymore, so you might want to take it up with the rules_docker people.

[Monnoroch]

Wait, I did read the code, and --quiet doesn't actually remove logs. That is precisely my point and the reason why I posted the issue here. I would expect this flag to make the software honor the fundamental Unix "silence is golden" principle (though to be honest I would prefer this do be the default), but it doesn't. This looks like a bug to me. Please correct me if I'm wrong.

[Monnoroch]

Oh, and I don't actually know how this is implemented in Bazel, but my suspicion is that remote caching computes a hash of the whole output of a dependent rule, including logs, while locally Bazel only looks at hashes of inputs for the current rule. But that's just my gut feeling and it might be more of a Bazel issue. The not working --quiet flag is a problem though.

[nkubala]

oof, yeah now that I'm looking at it that flag isn't working correctly. I'll take a look at that.

[Monnoroch]

Thanks! I also want to suggest inverting it: doing quiet by default and having a --verbose flag for debugging stuff.