Under documented breaking change in unix domain handling in v1.42

[howardjohn]

What version of gRPC are you using?

Trying out v1.42.0-dev.0.20211020220737-f00baa6c3c84

What version of Go are you using (go version)?

1.17

What operating system (Linux, Windows, …) and version?

Linux

What did you do?

grpc.Dial("unix:/test.sock")
grpc.Dial("unix://test.sock")
grpc.Dial("unix:///test.sock")

What did you expect to see?

All of them work, as is the case in v1.41 and older, or a clear release note describing the breaking change. Preferably the later, as the code I ran into issues is not my code so I cannot easily change it.

What did you see instead?

Case grpc.Dial("unix://test.sock") fails with panic: failed to build resolver: invalid (non-empty) authority: test.sock. I assume this is from #4817. The release notes there do not imply any breaking changes.

[easwars]

As per https://github.com/grpc/grpc/blob/master/doc/naming.md, the supported syntax for unix scheme is unix:path and unix://absolute_path. My line of thought is that we cannot release note possibly every behavior change, especially ones which were not supposed to work (but used to work), and now are not working. But I'm ready to convinced otherwise. @dfawley @menghanl

[howardjohn]

My line of thought is that we cannot release note possibly every behavior change, especially ones which were not supposed to work (but used to work), and now are not working

That is the exact thing I would expect to be release noted :-). gRPC is at the core of almost every large application these days. If I upgrade (or even before) and it stops working, the first thing I would check is release notes and expect that every behavioral change is documented.

All I am suggesting is a release note which seems like pretty minimal effort to add? Ideally it would actually follow a deprecation window.

[dfawley]

Argh. We spent a lot of time enumerating all the different user-visible behaviors to make sure we didn't break anything with this change, but it looks like we missed this one. 🤦

There was a test case that did unix://relative/path, but I think it was expected to fail before, but apparently because the path didn't exist: https://github.com/grpc/grpc-go/pull/4817/files#diff-b25c92b80601b564d1522420cd7c56d9d0aa7527299266f1256ac5fc5ac3d364R101

Sorry for the breakage! Since this was previously unintentional and undocumented behavior, I'm inclined to treat this as a bug fix and not a behavior change (so, no deprecation window). That said, now that we know there was a change, we should include a mention in the release notes.

[menghanl]

We will cover the behavior change in the 1.42 release notes.