Panic when a counter has an starting value of integer and then a float is pushed

[slok]

Hi!

First of all thanks for this project, specially gravel-gateway. I think that currently is the most usable/helpful Prometheus gateway out there.

Context

I encontered this problem while using gravel-gateway. However seems that the problem is related with the usage of this library, so I open the issue here, if you prefer to have the issue on the other repo, I will move it happily.

Problem

The problem itself is when I push a counter metric and randomly crashes the gateway with this error:

thread 'tokio-runtime-worker' panicked at 'called `Option::unwrap()` on a `None` value', /usr/local/cargo/registry/src/github.com-1ecc6299db9ec823/openmetrics-parser-0.4.2/src/public/model.rs:900:50

Findings

After reading some code (I don't know Rust) and making some tests I found that this happens when a counter has an integer value. E.g:

example_test_counter_total{foo="bar"} 0

And then a float is pushed. e.g:

example_test_counter_total{foo="bar"} 0.01

After this second push, the gateway crashes, but, if the metric starts with a float from the begining, there are no crashes, however is very common to initialize a metric to 0, leading to this use case.

Extra info

More information that could help:

• Gravel gateway version: v1.6.2
• Prometheus client: github.com/prometheus/client_golang v1.17.0
• Using the official process collector leads to this crashes on process_cpu_seconds_total counter metric.

[sinkingpoint]

Interesting! I'll take a look

[sinkingpoint]

This is fixed - will get a gravel gateway out with this soon

[slok]

Many thanks!!