Google-cloud-go: storage: Add exponential backoff for REFUSED_STREAM errors

[lhecker]

We're currently facing issues with GCS in production returning REFUSED_STREAM errors sporadically.
Would it be feasible to add the already existing exponential backoff logic (on 5xx and 429 errors) to REFUSED_STREAM errors as well?
It's currently in discussion for Go to add official support for this in https://github.com/golang/go/issues/20985, but until then it'd be awesome if the Google Cloud client libraries could already implement this manually.

What do you think? 🙂

[bradfitz]

Go won't have this until at least Go 1.10 so it makes sense to do it in the GCS library temporarily for 12-18 months until most Go users have the automatic version.

[adams-sarah]

@jba seems like we could just kill the check for if the error is a *googleapi.Error, no? Why is that there anyway? https://github.com/GoogleCloudPlatform/google-cloud-go/blob/master/storage/invoke.go#L32-L35

[lhecker]

@jba Is there a recommended strategy for handling this "issue" with GCS somewhere by the way?
I'm just wondering if pooling with more connections as a prevention might not be the better option than retrying since the latency might be lower that way, right?

[jba]

@lhecker I was planning on following the same logic that will be in Go 1.10.

[jba]

@shadams I'd rather we be conservative in what we retry. If the error is permanent the client would hang, which is harder to diagnose than if it fails fast.

@lhecker I actually just added the error to the list we normally retry. Turned out to be the simplest fix.

[lhecker]

@jba Thanks for the fix! We'll soon try it out again in production. 🙂
I do whonder though, if this really fixes the underlying usability problem with GCS... 🤔 Could it be it's actually (additionally?) a server side issue, where streams aren't load-balanced properly, for REFUSED_STREAM errors to not even happen? Because I've got the strong suspicion that this error might be HTTP/2-only and not happen with HTTP/1.1 at all, where you "naturally" use multiple TCP connections.

[jba]

You may be right; I don't know what's happening at the server.