RequestIdEnricher

Namespace: RA.Utilities.Logging.Core.Enrichers
Implements: Serilog.Core.ILogEventEnricher

The RequestIdEnricher class is a custom Serilog enricher that attaches a request correlation / trace identifier to every log event.

Its purpose is to make logs traceable and debuggable, especially in a microservices or distributed environment. When a single user action results in calls across multiple services, a consistent id lets you filter and find all related log entries across every system.

⚙️ How it works

RequestIdEnricher implements the single ILogEventEnricher.Enrich(LogEvent, ILogEventPropertyFactory) method, which Serilog calls for every event. It contributes one property: TraceId.

Resolving the value

The value comes from the first source that yields one, in this order:

1. The x-request-id HTTP request header — a correlation id sent by the client or an upstream proxy. This is the preferred source, because a value assigned at the edge stays stable as the request travels through multiple services.
2. HttpContext.TraceIdentifier — ASP.NET Core's unique identifier for a single request on a single server.
3. Activity.Current — through ActivityExtensions.GetActivityId(), for background work that has no HTTP request.

If none of the three sources produces a value, the TraceId property is still added, with a null value. The package never invents a random identifier, so unrelated events cannot be mistaken for part of the same trace.

How the value is written

The property is written with AddPropertyIfAbsent, so a TraceId already supplied by a logging scope is never overwritten. The HttpContext is resolved lazily inside Enrich(), through the stored IHttpContextAccessor — the enricher does not capture the context at construction time, so it works correctly regardless of when the logger is configured.

Properties Used

Property Name	Source
TraceId	x-request-id HTTP request header, otherwise HttpContext.TraceIdentifier, otherwise Activity.Current?.GetActivityId()

v10.1.1 — single TraceId property

Before v10.1.1 the enricher added two properties: a request-id property sourced from the x-request-id header, plus a separate TraceId. Since v10.1.1 the header value is folded into the single TraceId property. If you query, index, or alert on the old request-id property in your sinks, see the migration guide.

Constructors

Constructor	When it is used
RequestIdEnricher()	Uses a new HttpContextAccessor. This is the constructor Serilog calls when the enricher is activated by name from appsettings.json or through WithRequestIdEnricher().
RequestIdEnricher(IHttpContextAccessor contextAccessor)	Uses the supplied accessor, typically resolved from the dependency-injection container. Use this when you construct the enricher yourself.

Dependency

The enricher depends on IHttpContextAccessor to read the current request. Register it in your application with builder.Services.AddHttpContextAccessor() when you activate the enricher.

HttpContextAccessor stores the current context in a process-wide AsyncLocal, so the enricher's own accessor instance observes the same request as the rest of the application — but only while an IHttpContextAccessor is registered for ASP.NET Core to populate. Without an HTTP context, the enricher still resolves a value from Activity.Current when one is available.

Example

using RA.Utilities.Logging.Core.Enrichers;
using Serilog;

// Usually registered through configuration (WithRequestIdEnricher) rather than by hand.
// Construct it directly only when you need to supply your own IHttpContextAccessor.
var enricher = new RequestIdEnricher(httpContextAccessor);

Log.Logger = new LoggerConfiguration()
    .Enrich.With(enricher)
    .WriteTo.Console(
        outputTemplate: "{Timestamp:G} [{Level}] ({TraceId}) {Message:lj}{NewLine}{Exception}")
    .CreateLogger();