DateTime.UtcNow is not good enough for high precision durations in DiagnosticSource.Activity

[cwe1ss]

/cc @lmolkova @vancem

The new Activity class uses DateTime.UtcNow to calculate the duration of an activity. However depending on the system, the precision of DateTime might be at ~ 15ms.

I don't think this is precise enough for server scenarios.

In my OpenTracing instrumentation, I'm currently using a combination of DateTime + Stopwatch to overcome this issue. My code isn't in production yet though, so I'm not sure if this has any drawbacks.

[stephentoub]

https://github.com/dotnet/coreclr/issues/5061

[cwe1ss]

I've just seen that this behavior is already documented in the ActivityUserGuide. However I still think that the precision should be better by default. It's very hard to discover this behavior and writing a more precise DateTime+Stopwatch combination is quite complex/error-prone (Stopwatch runs out of sync, etc.)

@stephentoub thx for the link! Looking forward to see how this will be resolved.

[karelz]

Closing as dupe of https://github.com/dotnet/coreclr/issues/5061

[cwe1ss]

I don't think that's a duplicate. If there won't be a change to UtcNow this problem will still exist.

[karelz]

That's exactly what dotnet/coreclr#9736 does.

[cwe1ss]

great, thank you!