Adding metrics to client library

[tronda]

In order to identify and troubleshoot dotnet applications which have setup the client in a suboptimal way, we would like to have metrics from RabbitMQ's dotnet client. Since the RabbitMQ dotnet client already has a dependency towards System.Diagnostics.DiagnosticSource, adding metrics should be fairly straight forward with using the Metrics API from Microsoft. This is something our company would consider contributing to this library if the project agrees that this is a feature that it would like to have.

Based on semantic conventions for messaging client, the following metrics is something we consider interesting to add:

• messaging.client.operation.duration
• messaging.client.sent.messages
• messaging.client.consumed.messages

Additionally the following metrics could be considered (based on the semantic conventions for database client metrics):

• messaging.client.connection.count
• messaging.client.connection.max
• messaging.client.rabbitmq.channel.count
• messaging.client.rabbitmq.channel.max

We would like to get feedback is you consider that this something that would be valuable for the project.

[lukebakken]

I'm away until this Thursday. Please review prior issues and pull requests related to metrics and OpenTelemetry, such as this:

#1027

https://github.com/rabbitmq/rabbitmq-dotnet-client/issues?q=metric

There is probably overlap between metrics and OTel. @eerhardt probably has something to add with regard to this topic!

[michaelklishin]

@tronda

adding metrics should be fairly straight forward

our prior discussions with the OpenTelemetry team at MSFT suggest that it is often a lot more involved than it sounds. Not adding the code but agreeing on what to do, how to name things, what metrics to expose.

That said, if you believe it is straightforward, please take a look at the priori discussions, at what the client already supports, and submit a PR.

[BOLT04]

Hi @tronda , I think this discussion overlaps a bit with an existing one #1730. I agree adding metrics is beneficial, but like Michael said it's not straightforward and you can see prior discussions about this (e.g. #1730 ).
I haven't had time to do some tests but if you want to open a PR with your suggested implementation it would be awesome 👍