On 25.06.21 01:27, Shandong Dong wrote: > Ok, I will try the PR first. Can I know what‘s the concern of "Personally, > I'm still not sure if that's a sustainable approach. "?
We had a handful of requests in the past to add specific advanced statistics functions. In one case, a function was actually added, see https://prometheus.io/docs/prometheus/latest/querying/functions/#holt_winters The problem with the latter is that it was actually not the variety of Holt-Winters that most people wanted. A lot of misunderstanding happened because of that. My impression is (but I might be proven wrong) is that this is a rarely used PromQL function. But now we have to support it at least until the next major release. That latter problem will be avoided by feature flags. But if we now each of the five to ten persons that requested new functions will add on average two to three new functions, we end up with about 20 new functions, all with the same potential of being misunderstand. Many might be overlapping, so any new function needs to be reviewed for overlap with existing ones. Even if they are all behind feature flags, they will require a lot of code with potential interaction with existing code and with each other, so there is some maintenance overhead. Eventually, reviewing and acceptance of even more functions behind feature flags will slow down. So we are back at square one. And the multitude of experimental functions will make it harder for users to find the right one to try out. Which in turn will make it harder to identify the actually generally useful functions and "graduate" them. Realistically, there will be small groups of users liking subsets of functions, but rarely functions that aither everyone needs and likes or nobody. It feels a bit like the attempt to create a Python interpreter for data science that doesn't understand modules and instead tries to have all required functions built-in. That's hardly a reasonably approach. And that's why my personal idea is that Prometheus either has to keep stating that it is only meant for basic mathematical operations on metrics, or it has to provide some kind of "scripting interface" to allow custom mathematical "libraries" for users with special requirements. -- Björn Rabenstein [PGP-ID] 0x851C3DA17D748D03 [email] bjo...@rabenste.in -- You received this message because you are subscribed to the Google Groups "Prometheus Developers" group. To unsubscribe from this group and stop receiving emails from it, send an email to prometheus-developers+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/prometheus-developers/20210630212438.GO11559%40jahnn.
