Basic middleware unit propagation

[SirEdvin]

It would be nice if default middlewares, such as Delta and Average would propagate units from underline metric series.

[cyberbit]

I like this idea! I'll use a metric with item as the unit for the examples below.

How would you propose rate/irate units work? Propagation to avg/delta/idelta makes sense (average of item is item), but the rates can vary based on a provided time interval.

From https://telem.cyberbit.dev/reference/middleware/CalcDelta#interval:

The format is (unitScale)(unit), where unitScale is an integer greater than 0, and unit is one of: s (second), m (minute), h (hour), d (day).

First option: Append the measurement interval to rate/irate units. If the default interval of 1 second is used, the rate is simply item/s, but this has the potential to quickly fall apart with custom rates. An interval of 5 minutes would result in a unit of item/5m, which feels a little silly. Not to mention plural nouns being a non-trivial problem to solve (item/s vs items/s, across all supported units, even custom ones!).

Second option: All units are passed through as-is (item for everything). It would be up to the user if they care to append the precise measurement interval.

I think I prefer the second option, but am interested in your thoughts.

[SirEdvin]

Well, if you ask me, I would actually do both, by providing interface for unit transformation function and then have two default modes.

Something like:

telem.middleware.calcDelta("1m", "passthrough") -- would lead to just copy units
telem.middleware.calcDelta("1m", "transform") -- would lead to (unitScale)(unit)
telem.middleware.calcDelta("1m", function(metric) return "my_new_powerful_unit" end)  -- would lead to using provided unit

[hooded-person]

I agree with @SirEdvin on this. I would like to add that I think "transform" would be a reasonable default for this.

If you had to choose between one of them I would say transform is the better option, because it makes sure changes in ex. the interval propgate down to the unit and when its displayed. If you let it to the user to add the time interval behind it, this will most likely lead to the value being hardcoded in many spots, which will be a pain if they later decide they would want to change the interval.