Using mime-type in prometheus parser to handle protocol-buffer responses

[Aladex]

Fixed #8366

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[srebhan]

Just two minor comments. One is in the code, the other one is: Could you please improve the PR-message to e.g. something like "Using mime-type in prometheus parser to handle protocol-buffer responses".

[srebhan]

Wow that was fast @Aladex! :-)

[srebhan]

Looks good to me.

[ssoroka]

Looks great. Thank you!

Can we get a test to protect against regressions here?

[Aladex]

Looks great. Thank you!

Can we get a test to protect against regressions here?

Maybe, but i don't know how to do it :-(

[srebhan]

@Aladex you need one test-data sample in protocol-buffers format. The you start a small http-server to serve this sample to the plugin. Check prometheus_test.go (last test-case) to get an idea on how to do it...

[Aladex]

@Aladex you need one test-data sample in protocol-buffers format. The you start a small http-server to serve this sample to the plugin. Check prometheus_test.go (last test-case) to get an idea on how to do it...

Yes, but here we have examples with classic httptest.NewServer. How do i make such tests with the protobuf server?

[srebhan]

Let me understand this, I thought you query a http-server and get back a response with the mime-type set to protocol buffers and the message content is a binary protocol-buffer frame. Is this correct? If so, you can use the httptest.NewServer example, set the response header (e.g. https://www.lemoda.net/go/override-mime-type/index.html) of the answer and embedd serialized protocol-buffer data. The protocol-buffer data you might be able to generate from a real request to a real server offline and then just add the bytes as a variable (or file if it is larger).

[Aladex]

@srebhan hi. Can u review my latest changes?

[srebhan]

Looks perfect.

[ssoroka]

Thank you!