How can I create a Serilog enricher that reads from HttpContext.TraceIdentifier?

Question

I've recently integrated Serilog into several .NET Standard class libraries, including some class libraries that are used by MVC 6 projects. What I'd like to do is enrich log entries with HttpContext.TraceIdentifier. I wrote an action filter that sets HttpContext.TraceIdentifier to a Correlation-ID request header value, if present:

public override void OnActionExecuting(ActionExecutingContext context)
{
    StringValues correlationIds;
    Guid correlationId;

    if (!context.HttpContext.Request.Headers.TryGetValue(Constants.CorrelationIdHeaderName, out correlationIds) || correlationIds.Count != 1 || !Guid.TryParse(correlationIds[0], out correlationId))
    {
        correlationId = _guidFactory.Random();

        context.HttpContext.Response.Headers.Add(Constants.CorrelationIdHeaderName, correlationId.ToString("D"));
    }

    context.HttpContext.TraceIdentifier = correlationId.ToString("D");

    base.OnActionExecuting(context);
}

The problem is, how do I make Serilog aware, for the life of this request, of the correlation ID? Since it doesn't appear as though there is an HttpContext.Current property, I'm not sure how to create an enricher that will work. Is this even possible?

user764754 · Accepted Answer · 2016-11-22T16:19:42.650

11

I don't think you need an enricher for this.

Putting {RequestId} into the sink's outputTemplate gives me an ID like "0HL0GJPLR7AOD". If I set HttpContext.TraceIdentifier right before logging something then {RequestId} gives me exactly that ID so custom IDs also work with {RequestId}.

I think {RequestId} is a Microsoft.Extensions.Logging feature but it works out of the box with serilog (at least when you are using Serilog.Extensions.Logging).

Update: Don't forget to configure Enrich.FromLogContext().

edited Nov 22 '16 at 16:19

answered Nov 19 '16 at 17:15

user764754

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I will give this a try. Thanks! – NathanAldenSr Nov 19 '16 at 17:41
How would I do this using `JsonFormatter`? There is no `outputTemplate` parameter in that case since Serilog serializes objects. – NathanAldenSr Nov 28 '16 at 15:28
@NathanAldenSr I don't know about `JsonFormatter` but `CompactJsonFormatter` automatically includes all the event properties like `RequestId` as JSON object properties like `"RequestId":"0HL0NKROIGJ8O"` – user764754 Nov 28 '16 at 15:59
Cool, thank you. I am working on this now; I'll let you know how it goes. – NathanAldenSr Nov 28 '16 at 16:07
Everything you mentioned checks out! Thanks so much for this. – NathanAldenSr Nov 28 '16 at 16:24
@user764754 - Doesn't seem to work on .Net Core 3.1, I just get empty string for RequestId in my log file – dcp Jul 14 '20 at 22:29
Is it possible to use `Activity.Current?.Id` instead of `HttpContext.TraceIdentifier` ? – Sentouki May 30 '22 at 00:03

How can I create a Serilog enricher that reads from HttpContext.TraceIdentifier?

1 Answers1