Exposing prometheus metrics failing with 500 error

[Geet Manghnani]

I get the following error in some situations.

```

was collected before with the same name and label values

```

On the restart of the target service where the metrics are exposed, It exposes the metrics initially but later start throwing 500 to the prometheus on scrape.

On accessing the /metrics endpoint, I see this in the return.

was collected before with the same name and label values

Could someone help me understand why I am getting this error?

I am using golang client of prometheus 

Looks like the error is being thrown from this line.
https://github.com/prometheus/client_golang/blob/main/prometheus/registry.go#L908

I am using go fiber to expose the metrics.

func MetricsRoutes(api fiber.Router) {

api.Get("/metrics", adaptor.HTTPHandler(promhttp.Handler()))

}

On my local setup It works fine and only in some environment, i get the. 500 error