Cross Process Context Propagation

Following the OpenTracing standard, you must arrange for your application's WavefrontTracer to propagate a span context across process boundaries whenever a client microservice sends a request to another microservice. Doing so enables you to represent the client's request as part of a continuing trace that consists of multiple connected spans.

The WavefrontTracer provides Inject and Extract methods that can be used to propagate span contexts across process boundaries. You can use these methods to propagate ChildOf or FollowsFrom relationship between spans across process or host boundaries.

• In code that makes an external call (such as an HTTP invocation), obtain the current span and its span context, create a carrier, and inject the span context into the carrier:
  Example:

  currentSpan = ...  // obtain the current span
  ITextMap carrier = new TextMapInjectAdapter(new Dictionary<string, string>());
  tracer.Inject(currentSpan.Context, BuiltinFormats.HttpHeaders, carrier);
  
  // loop over the injected text map and set its contents on the HTTP request header...
  

• In code that responds to the call (i.e., that receives the HTTP request), extract the propagated span context:
  Example:

  ITextMap carrier = new TextMapExtractAdapter(new Dictionary<string, string>());
  ISpanContext ctx = tracer.Extract(BuiltinFormats.HttpHeaders, carrier);
  IScope receivingScope = tracer.BuildSpan("httpRequestOperationName").AsChildOf(ctx).StartActive(true);