Serilog: Log Event Id as the data type that was inserted into LogInformation

[ptsneves]

Does this issue relate to a new feature or an existing bug?

• [ X ] Bug
• [ ] New Feature

Serilog.AspNetCore 2.1.1

In the current behaviour when I call Log logger.LogInformation(1000, "My message), the EventId gets serialized as {"EventId": {"Id": 1000}}.

I would expect {"EventId": 1000}. This would force it to be a scalar which is what I desire. I think this is a bug, as this somehow changes the expected semantics described in the AspNetCore Logger documentation. Am I missing something?

Edit: I tried to use the Destructuing primitive but it is never called, so I cannot proceed further.
.Destructure.ByTransforming<EventId>(r => r.Id)

[nblumhardt]

Hi @ptsneves, thanks for the heads-up.

EventId can carry both the name and numeric identifier at the same time:

https://github.com/aspnet/Logging/blob/2d2f31968229eddb57b6ba3d34696ef366a6c71b/src/Microsoft.Extensions.Logging.Abstractions/EventId.cs#L23

Representing it as a struct was the only full-fidelity option that would make queries like EventId.Name = 'foo' behave predictably.

To change this, though, you can plug in an ILogEventEnricher like:

    .Enrich.With<EventIdIsAlwaysNumericEnricher>()

implemented something like (untested code warning!):

class EventIdIsAlwaysNumericEnricher : ILogEventEnricher
{
    public void Enrich(LogEvent evt, ILogEventPropertyFactory _)
    {
        if (evt.Properties.TryGetValue("EventId", out var val) &&
            val is StructureValue sv &&
            sv.Properties.TryGetValue("Id", out var idval))
        {
            evt.AddOrUpdateProperty("EventId", idval);
        }
    }
}

🚀

[ptsneves]

Hello @nblumhardt
Thanks for the answer. I was for a long time trying to figure out how to do that with an enricher but was stuck with the concept that adding a property that already existed seemed to not make sense. You provided the key piece. Thank you very much.

Regarding the destructure. Do you know why it did not work?

[nblumhardt]

Great, thanks @ptsneves !

RE destructuring, the event id is mapped across explicitly, without invoking the configured IDestructuringPolicys. We could probably enable this, but at some performance cost - for now I think the enrichment route may be the best one. Cheers!

[ptsneves]

Thanks!