Benzene

Correlation Ids

Cross-service correlation is handled by automatic W3C traceparent propagation (UseW3CTraceContext()), which continues a distributed trace from the incoming traceparent/tracestate headers on every transport.

What remains

ICorrelationId and its log-scope enrichment are still available. WithCorrelationId() attaches a correlationId value to the logging scope (via ILogger.BeginScope):

.UseLogResult(x => x.WithCorrelationId());

With nothing populating it, ICorrelationId self-generates a GUID per scope — useful as a per-invocation marker in logs. To populate it from a custom source (e.g. a partner's proprietary header), register AddCorrelationId() and call ICorrelationId.Set(...) from your own middleware:

app.Use("PartnerCorrelation", resolver => async (context, next) =>
{
    var headers = resolver.GetService<IMessageHeadersGetter<MyContext>>();
    resolver.GetService<ICorrelationId>().Set(headers.GetHeader(context, "x-partner-request-id"));
    await next();
});

Outbound clients can still forward the value: .UseCorrelationId() on an outbound route pipeline (see Clients — Outbound middleware) stamps the current ICorrelationId onto the outgoing request's headers under the x-correlation-id key by default (CorrelationHeaderDefaults.HeaderKey, matching wire-contracts.md's own example) — the same key the inbound diagnostics span tag (benzene.correlation-id, set by AddDiagnostics()'s middleware decorator) reads by default, so the two directions join up without any configuration.

The key is configurable in one place for both directions: register a Benzene.Abstractions.CorrelationHeaderOptions in ConfigureServices and both CorrelationIdMiddleware and the diagnostics decorator pick it up. .UseCorrelationId(correlationKey) and CorrelationIdMiddleware's constructor also still take a correlationKey parameter to override per call, which wins over a registered CorrelationHeaderOptions:

services.UsingBenzene(x => x.AddSingleton(new CorrelationHeaderOptions { HeaderKey = "x-tenant-correlation-id" }));

An explicit per-call header wins: if the outgoing message already carries a header under the same key (e.g. via IBenzeneMessageSender.SendAsync's per-call headers parameter), the middleware leaves it untouched instead of overwriting it with the ambient — possibly self-generated — value.

See Also