Remove the Format method of stats.Sink

[oleiade]

Proposal

During our discussions about parsing and executing thresholds directly in Go, @mstoykov mentioned that we could get rid of the stats.Sink.Format method all in all.

Context

I would also, looking at this code and the other places where sink.Format is used, I kind of want to remove this method. It's in most cases used as a way to get info about values for the given sink, but then we also cast the sink to its concrete type in order to get even more info from it.
Given that there are 4 sink types, I feel like a switch in all cases (as the fields might not be the same) might be better 🤔.
Especially as it turns out that the CounterSink does actually return a rate, but the summary code overwrites it, possibly with the same value 🤦
And in the REST API where it is used "correctly" we have a minor bug about Trends and also doesn't show the same stuff as in the summary 🤦.

Status

I only report this issue as it was mentioned during a somewhat related discussion. There must be some missing context, questions, and related issues that probably need mention and being addressed before moving on. Thus, this issue could use more input from historical maintainers. Don't hesitate to provide any information or feedback you judge necessary to the resolution of this, I will add them as edits to this description.

Related

• Fix/1443 remove the JS runtime from threshold calculations #2251
• Remove the JS runtime from threshold calculations #1443
• comment in context

[yorugac]

Just a note: this change will require modifications in Prometheus remote-write extension as it relies on current Sink interface.