Add timestamp and duration to Diagnostics Source events

[avanderhoorn]

Given the precedence of what we have here aspnet/Hosting#543 I'm adding timestamp data to these events - this ensures that everyone is working from the same base data when talking timings.

In addition, I'm adding duration to the finish events so that consumers only have to subscribe to finish events in order to determine what the duration for a given piece of middleware is. This change is localized to the scope of code where we know that we have listeners interested in the result and hence isn't on the primary execution path.

[dnfclas]

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[Tratcher]

@lodejard @rynowak @Eilon

[Eilon]

These lines are getting a tad long - can you wrap them like:

_diagnostics.Write(
    "Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareStarting",
    new
    {
        name = _middlewareName,
        httpContext = httpContext,
        instanceId = _instanceId,
        timestamp = startTimestamp, // and include this trailing comma :)
    });

[Eilon]

@kichalla please review & merge when you have a chance.

[kichalla]

In addition, I'm adding duration to the finish events so that consumers only have to subscribe to finish events in order to determine what the duration for a given piece of middleware is.

If users subscribe only to the finish event, then the startTimestamp would be zero causing the duration to be incorrect. Should we always capture startTimestamp then? (but yeah i see you mention about primary execution path)

[dnfclas]

Hi @avanderhoorn, I'm your friendly neighborhood .NET Foundation Pull Request Bot (You can call me DNFBOT). Thanks for your contribution!
You've already signed the contribution license agreement. Thanks!

The agreement was validated by .NET Foundation and real humans are currently evaluating your PR.

TTYL, DNFBOT;

[avanderhoorn]

Whoops didn't meant to close... reopend.

[avanderhoorn]

Ok, I've updated things to fix the line breaks. Additionally, I've updated things so that the startTimestamp is always captured. If we are worried about always capturing that, we can update things to only capture it if either the MiddlewareFinished or MiddlewareException are being listened to, but that check could be more expensive than just capturing the value.

[kichalla]

[Eilon]

Ah yeah I like this fix - I'd like the data to always be accurate, when available.

[kichalla]

f387d04