The Prometheus exporter fails with an error by default

[MrAlias]

The resolution to #7066 causes the Prometheus handler to fail on invalid metrics. By default we do not convert things like ""go_gc_duration_seconds" (type summary) which the Prometheus HTTP handler adds by default.

This means that by default now our exporter fails the HTTP handler with a 500 for the invalid metric.

Users need to explicitly disable this failure mode to use the exporter given we do not support these types and they cannot fix the error.

How to reproduce

Run the TestMetricProducerPrometheusWithPrometheusExporter test for the v1.38.0 release of that module using the latest release of the prometheus exporter (v1.39.0). It now fails by default complaining there is an invalid metric type for at least the mentioned "go_gc_duration_seconds".

[MrAlias]

cc @dashpole

[MrAlias]

Work around example: open-telemetry/opentelemetry-go-contrib@0518466

[dashpole]

Ouch. This probably needs at least a partial revert, and a patch release

[MrAlias]

This is caused because the autoexport package uses both the prometheus bridge and the exporter:

https://github.com/open-telemetry/opentelemetry-go-contrib/blob/14c6a7a655bb5d915dc3939aef2cff9df65c3a6c/exporters/autoexport/metrics.go#L215

These should not be mixed.

[MrAlias]

Closing. This is not a bug.

As mentioned above, the prometheus bridge and exporters should not be used together. This is addressed in the autoexport package where that mixing was occuring.