I discovered a rather awesome library that behaves something like a mini RRD timeseries database, especially for telemetry metrics. It’s named “Mobius”, but the author seems rather shy to promote it, but I found it a gamechanger, so want to give it a quick plug!

A little story I think explains why I think this is cool: I am aware that Elixir has support for “telemetry” to generate metrics and the like. I buy why adding support for this to my application is useful, but … As I don’t have an infrastructure set up to monitor/aggregate/graph these metrics, I’ve never really bothered to implement any… What can they do for me? Perhaps I write some code to investigate a performance problem and then forget about it later…

So that’s where we come in, and then I discovered the Mobius library. Essentially it builds a simple RRD database, storing the last X seconds of measurements, which roll to become the last Y minutes, then the last Z hours, and so on. It also has a basic graphing library which works in the console (wow!), and also you can export the data to graph in Livebook, etc

It’s hard to describe the “oh my” moment, but suddenly being able to visualise a bunch of metrics was a game changer! My app deals with a cellular modem and byte counters and signal strengths and the ability to suddenly get a quick graph of the last few minutes or last few hours of usage was a wow moment. It’s not that I couldn’t get that data and graph it before, but the amount of friction was high.

Now that I can quickly visualise some statistics I’m sticking telemetry everywhere I can! Previously I might have wondered how fast some function took to execute and if it really worried me I might have built a benchmark and then forgotten about it later is the performance seemed ok. Now I can just add some telemetry to any function that seems interesting and then poke at it later! Very probably I will also use this to expose some data to the end user in our app as well (think spark lines, etc)

I found this through a video from last year’s ElixirConf here:
https://www.youtube.com/watch?v=KDrNru8XXQo

I’ve not seen any coverage of it here, and I think the reason is because it’s not been pitched as a mini Timeseries/Grafana. However, for my use case this is exactly what it’s replacing - sure it’s not got anything like the functionality of Influx, but for getting off ground zero and making metrics useful, I claim this does more than 50% of what I could do with the big guns (plus it’s built into Elixir and could be used to expose these metrics to a front end app.

The library lives here:

• GitHub - mobius-home/mobius: Library for localized telemetry reporting · GitHub

However, I have added quite a few enhancements here (pull request sent to author):

• GitHub - ewildgoose/mobius: Library for localized telemetry reporting · GitHub

I can provide some examples of plotting in LiveBook if anyone wants to see that?

Enjoy!