[Hosting] Add {OriginalFormat} to start & stop log state objects

[CodeBlanch]

Description

The ILogger extensions and source generator return the original template logged as the {OriginalFormat} key on the IReadOnlyList<KeyValuePair<string, object>> state representing the log being written.

AspNetCore has a couple custom log states which do not mirror the {OriginalFormat} behavior. By default OpenTelemetry only captures message templates but for these logs it must either have empty template/body (confusing for users) or invoke ToString (and incur allocations) to generate a formatted string because no template is available.

In order to make these high value logs play nicely with structured logging and to enable high performance capture I'm proposing we should mirror the {OriginalFormat} behavior.

Changes

• Returns {OrignalFormat} as the last key on HostingRequestStartingLog & HostingRequestFinishedLog state objects
• Tweaks the log messages to be more consistent & deterministic...
  • Start log now writes content type & length after a "-" character
  • Stop log no longer writes out request content type & length

Final templates look like this:

Start:
Request starting {Protocol} {Method} {Scheme}://{Host}{PathBase}{Path}{QueryString} - {ContentType} {ContentLength}

Stop:
Request finished {Protocol} {Method} {Scheme}://{Host}{PathBase}{Path}{QueryString} - {StatusCode} {ContentLength} {ContentType} {ElapsedMilliseconds}ms

/cc @davidfowl @tarekgh @noahfalk @cijothomas @utpilla @reyang

[ghost]

Thanks for your PR, @CodeBlanch. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[BrennanConroy]

If we're going to do this, we should do it for all our custom logging:
https://grep.app/search?q=IReadOnlyList%3CKeyValuePair%3Cstring%2C%20object%3F%3E%3E&filter[repo][0]=dotnet/aspnetcore

[CodeBlanch]

@BrennanConroy Thanks for the link! I don't think {OriginalFormat} is really needed on scopes. HttpRequestLog & HttpResponseLog probably need it, but not sure what the template would be exactly. In any case, happy to look into those things if this goes in 👍

[adityamandaleeka]

cc @samsp-msft

[halter73]

Agreed about the scopes. Even for the HttpLogging middleware, I don't think there's a great {OriginalFormat} since it's so dynamic. I think we should just take this as a starting point. If someone else has a good idea for the other logs, we can merge that separately.