Add Guidance wrt Labelling to Naming and Rules Best Practices

[conallob]

Add Guidance wrt Labelling to Naming and Rules Best Practices to docs/practices/naming.md and docs/practices/rules.md, specifically:

• The primary purposes of job and instance
• Include WARNINGS about accidentally stripping the job label, especially in multi-tenant systems

This Fixes #2690

[conallob]

Friendly ping @SuperQ @beorn7 ?

[conallob]

Obligatory post-it note reminder: https://photos.app.goo.gl/Bkfir4wRiLtNVG4W8

[beorn7]

With my current patchy availability, there is little chance I get to this anytime soon. Maybe @juliusv has a qualified opinion here?

[conallob]

Friendly ping @SuperQ @juliusv

[andrechalella]

Hey @conallob, congrats for the nice PR!

Just one thing: maybe you could fix the eaach typo in

• The job label is a primary key to differentiate metrics from eaach other.

There is a small confusion I would love to see fixed, in a paragraph just below one of your edits. It is:

To keep the operations clean, _sum is omitted if there are other operations,
as sum().

I don't understand the as sum() part. Like, "x is omitted if there are other operations such as x"? It doesn't make sense to me, in a very basic way. I know it's out of the scope of this PR, but maybe you could touch it to clarify.

[conallob]

Hey @conallob, congrats for the nice PR!

Just one thing: maybe you could fix the eaach typo in

• The job label is a primary key to differentiate metrics from eaach other.

There is a small confusion I would love to see fixed, in a paragraph just below one of your edits. It is:

Fixed the typo.

To keep the operations clean, _sum is omitted if there are other operations,
as sum().

I don't understand the as sum() part. Like, "x is omitted if there are other operations such as x"? It doesn't make sense to me, in a very basic way. I know it's out of the scope of this PR, but maybe you could touch it to clarify.

I'm afraid that best practice is unrelated.

It also makes sense as written, once you've written enough rules. It's weighing up the trade-off between tracking the chain of operations across a pipeline of rules vs the rule name growing unwieldy. Many of these best practices trace back to specific philosophies from Prometheus' predecessor.

If you still think it needs a polish, please a separate doc bug.

[conallob]

Ping @juliusv , since @SuperQ is currently unavailable for life reasons