current head of master: POST requests start to break with Content-Encoding "snappy" not supported

[jgehrcke]

In our CI we POST snappy-compressed protobuf messages to /loki/api/v1/push. In such POST HTTP requests we set these two headers:

      "Content-Type": "application/x-protobuf"
      "Content-Encoding": "snappy"

This has worked with all previously released versions of Loki.

Now we are testing with Loki's current head of master (cb59069). It emits a 400 Bad Request response, with the error message

Content-Encoding "snappy" not supported

The change in behavior is a side effect of this patch: https://github.com/grafana/loki/pull/3291/files

Should we change our HTTP request headers because they are obviously wrong, or is this a bug introduced with #3291?

The Prometheus remote_write HTTP API I believe "wants" to be used with this set of headers:

	httpReq.Header.Add("Content-Encoding", "snappy")
	httpReq.Header.Set("Content-Type", "application/x-protobuf")
	httpReq.Header.Set("X-Prometheus-Remote-Write-Version", "0.1.0")

(inferred from Proms' storage/remote/client.go)

Does X-Prometheus-Remote-Write-Version: 0.1.0 have any meaning for Loki?

[cyriltovena]

I'm even more impressed by the defer in this function closing the reader before returning.

Gzip might not even be working.

EDIT: the defer is fine.

[cyriltovena]

btw to answer your question this is a bug.

[ukolovda]

@jgehrcke , I append several test for HTTP parser.
But I have no experience with Protobuf. Please append your test cases, if you can.