Add PromQL info function blog post

[aknuds1]

I'm proposing to add a blog post on the PromQL info function! During the last PromCon, a revelation was that the info function is too poorly marketed. One potential remediation mentioned was writing a blog post :)

[ywwg]

This is great! I made a few comments

[beorn7]

Sorry for the avalanche of comments. Here are my main lines of thought (from which most comments derive):

• We should really focus on the cases where info is much more simple than the traditional query:
  1. All data labels are copied. (You have covered this case, but always further down; it should be the very first case to show, though.)
  2. Filtering for label value. (You haven't covered this case at all.)
• Rather than reinforcing the misconception that info is merely solving a syntactic problem (which could be read as info being merely syntactic sugar), we should clarify that the problem of the complex join queries is caused by the amount of information the user has to specify and that info solves this by deducing this information from other sources (or just using heuristics for now, which also explains the shortcomings of the current implementation).
• We should be very upfront about the missing parts, both that they are relevant but also that we want to work on them. That's partially already the case, but as explained in comments, it could be clearer. What we should also add is that the tooling outside of PromQL proper doesn't really handle the info function appropriately yet, e.g. autocomplete or query builders. (Many issues Patrick reported were about exactly those deficiencies. But for him, it appeared as fundamental problems of info and not as an incomplete implementation.)

[beorn7]

Will have a look ASAP. (I'm saying that to many these days… it might not be very soon…)

[aknuds1]

Thanks @beorn7!

[beorn7]

A few more things, but looking very good already.

Note that the date in the filename needs to be updated to the actual date of publication.

[ywwg]

Can we make "Giving Feedback" a heading so it's more eyecatching? Right now it's buried at the end of the post -- make it really easy for people who want to talk back to do so.

[aknuds1]

Can we make "Giving Feedback" a heading so it's more eyecatching?

@ywwg @beorn7 I moved requests for feedback to a single section "Giving Feedback", just before the "Conclusion" section. WDYT?

[beorn7]

I'm traveling until Dec 16. My remaining items were not very significant, and I trust you to address them appropriately, so as soon as the other reviewers are happy, assume I am, too, and don't wait for my explicit approval.

[ywwg]

this looks great, thank you!

Dismissing stale review as @beorn7 says it's good to go, given Owen's approval.