Swallow exceptions from ObserveDurationAsync, but throw from Func input?

[cscoon]

We wrap our Prometheus metric emitting calls in a wrapper class which essentially catches any exceptions thrown while incrementing a metric and swallows it. The reason is that if we are performing an important business process, we would rather ignore the exception from IncTo than have it throw an exception and end the business process.

This works great for most Prometheus.Client methods such as IncTo. But the practice breaks with ObserveDurationAsync because that method accepts the code snippet that should be timed as a Func. So both pieces of code are executed in a single call.

What we'd like to do is ignore/swallow any exception that results from ObserveDurationAsync, but throw any exception that results from the Func execution.

Does Prometheus.Client provide a pattern for doing this?

[sanych-sun]

No. We do not have anything like this for now, but probably can add this as a extension method argument or even metric config. The first approach allow us to localize the changes, but last one looks more generic. But not sure if it makes sense.

@phnx47 what do you think? Is adding new metric family configuration (for any kind of metric metrics) to ignore any exceptions while observations is valuable? I mean suppress any exception that could appear inside Inc, Dec, etc methods. If we go this way we probably have to at least report the exception to diagnostics source.

[phnx47]

I didn't fully understand the current problem. ObserveDuration and ObserveDurationAsync just extensions, so can implement other extensions.

@cscoon Maybe you can create PR with your suggestions?

[phnx47]

Issue here: #183