Better trace op names for querier

[gouthamve]

DON'T MERGE, depends on weaveworks/common#126

It separates the /metrics calls from queries now.

[bboreham]

What's the justification for this change? The different strings don't seem that much better that it warrants 47 extra lines of code.

[gouthamve]

Well having /metrics interspersed with query makes it hard to pick the right trace, while that in itself is not that big of an issue, we cannot control the sampling for both separately. We currently sample all our queries and that get includes a ton of /metrics calls.

[tomwilkie]

I wonder if we can use https://github.com/weaveworks/common/blob/master/middleware/instrument.go#L66 to correct label the traces, as we do with the labels in the histograms?

[bboreham]

Maybe a screen-grab would help? I can't recall ever having a problem with metrics calls interspersed.

[gouthamve]

This is the same for querier and it's the same op for queries. Now I look for other operations when looking for queries, but I'd like to be able to not sample these.

Also, I implemented Tom's suggestion and the code is much smaller now :) Like 10-ish lines :P

[gouthamve]

Updated the vendoring to use upstream. Should just work now. Good to take a look.

[tomwilkie]

LGTM - lets test in dev first before merging though.

[tomwilkie]

Works spot on: