Package io.opentelemetry.context.propagation

Interface ContextPropagators

@ThreadSafe public interface ContextPropagators
A container of the registered propagators for every supported format.

This container can be used to access a single, composite propagator for each supported format, which will be responsible for injecting and extracting data for each registered concern (traces, correlations, etc). Propagation will happen through Context, from which values will be read upon injection, and which will store values from the extraction step. The resulting Context can then be used implicitly or explicitly by the OpenTelemetry API.

Example of usage on the client: 


 void onSendRequest() {
   try (Scope ignored = span.makeCurrent()) {
     ContextPropagators propagators = openTelemetry.getPropagators();
     TextMapPropagator textMapPropagator = propagators.getTextMapPropagator();

     // Inject the span's SpanContext and other available concerns (such as correlations)
     // contained in the specified Context.
     Map<String, String> map = new HashMap<>();
     textMapPropagator.inject(Context.current(), map, new Setter<String, String>() {
       public void put(Map<String, String> map, String key, String value) {
         map.put(key, value);
       }
     });
     // Send the request including the text map and wait for the response.
   }
 }

Example of usage in the server: 


 private final Tracer tracer = openTelemetry.getTracer("com.example");
 void onRequestReceived() {
   ContextPropagators propagators = openTelemetry.getPropagators();
   TextMapPropagator textMapPropagator = propagators.getTextMapPropagator();

   // Extract and store the propagated span's SpanContext and other available concerns
   // in the specified Context.
   Context context = textMapPropagator.extract(Context.current(), request,
     new Getter<String, String>() {
       public String get(Object request, String key) {
         // Return the value associated to the key, if available.
       }
     }
   );
   Span span = tracer.spanBuilder("MyRequest")
       .setParent(context)
       .setSpanKind(SpanKind.SERVER).startSpan();
   try (Scope ignored = span.makeCurrent()) {
     // Handle request and send response back.
   } finally {
     span.end();
   }
 }