Consider supporting sorting by label value

[juliusv]

Mainly for display reasons (tabular view), it would be sometimes useful to not sort by the value of timeseries, but by a given label value.

Example: list all apps in a PaaS and their memory usage. It would be nice to be able to sort by application name ("app" label).

/cc @grobie

[brian-brazil]

The console templates already support sorting by label with the sortByLabel function, and a sortByValue would make sense too.

I'm not sure it makes sense for prometheus API itself to offer this, as this is a presentation issue rather than a calculation. It gets into questions about what ordering properties the various operators and functions should have.

[juliusv]

@brian-brazil The reason why I'd prefer this as a query-language function so far, is:

• console template functions don't help people who are running ad-hoc queries, like @grobie was doing (the mentioned example)
• it would be quite a specialized feature, so adding buttons/fields in the UI for it would yield a very low ratio of "usefulness to the average query" / "cost of always having those UI elements there".

[brian-brazil]

What was he running the ad-hoc query with? The output of the /query interface isn't human-readable.

[juliusv]

@brian-brazil He was using the tabular view under /graph.

[brian-brazil]

I think there should be an ordering on the table output on /graph (e.g. sort the full name of the metric), done in say the JS.

[brian-brazil]

See #432

[RichiH]

Sorry, I looked for dups, but didn't see this one.

I agree with the discussion in #432 that this should be in one layer only. As you don't know where further consumption of the results happens, e.g. Grafana, via HTTP API, etc, I do think that this should be done in PromQL itself as that opens one canonical way of sorting for all further processing methods.

[brian-brazil]

#1533

[gouthamve]

This is the default in 2.0. I think this issue can be closed @brian-brazil @fabxc

[lock]

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