How to prefix metric names? about prometheus-fastapi-instrumentator

[trallnag]

Hey @codyflynnNC, I'd prefer not to include a metric_namespace attribute in the instrumentation module. The idea is to separate the actual definition of the metrics (here) and the instrumentation (here)that gets data from FastAPI. If we add metric_namespace a user would assume that it will be respected by all functions you can find in the metrics module which is not the case.

If you want to set the namespace go for:

instrumentator.add(metrics.default(metric_namespace="name_space"))

Or add your own function instead which gives you more control. If you have other questions I'm happy to help

[cmflynn]

So after looking through the source code, it seems the default instrument function:

if len(self.instrumentations) == 0: self.instrumentations.append(metrics.default())

while the instantiation of the class does not take in instrumentation args. I'd propose a change to the instantation of the class to take in the namepsace arg, then pass that into if len(self.instrumentations) == 0: self.instrumentations.append(metrics.default(metric_namespace=self.metric_namespace))

if this makes sense im happy to create a PR

[cmflynn]

Thanks for the quick response. that works perfectly. I'll close this issue.