Proxy supplies metrics for monitoring performance

[samsp-msft]

Collect metrics for all stages of the proxy processing, including outbound http requests

[samsp-msft]

@davidsh - if you have existing issues in the dotnet repo, we should tag those here, and they will appear in the board(s)

[analogrelay]

Whoops, I created #63 and missed this. I'll add my expanded info to this and close #63.

[analogrelay]

In order to provide the detailed diagnostics proxy users will want, we need to expand the diagnostics and tracing support throughout the networking stack.

This includes both counters (using EventCounters) and tracing (using EventSource). It covers the low-level sockets API, as well as higher level APIs like HttpClient.

Another aspect to consider here is dimensions. We believe it is important for users to be able to specify the "scope" of a particular network operation and include custom dimensions like Route identifiers, backend names, etc. For v1 we believe it is sufficient to express these in the EventSource events, and keep the counters high-level.

[davidsh]

Linking: dotnet/runtime#37428