Support sampling on az.namespace attribute (#42548)

Author: trask

sdk/core/azure-core-tracing-opentelemetry/src/main/java/com/azure/core/tracing/opentelemetry/OpenTelemetryTracer.java

@@ -31,6 +31,8 @@
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
+import static java.util.Collections.singletonMap;
+
 /**
  * Basic tracing implementation class for use with REST and AMQP Service Clients to create {@link Span} and in-process
  * context propagation. Singleton OpenTelemetry tracer capable of starting and exporting spans.
@@ -148,16 +150,15 @@ public Context start(String spanName, StartSpanOptions options, Context context)
             spanBuilder.setStartTimestamp(options.getStartTimestamp());
         }
 
-        Span span = spanBuilder.startSpan();
-        if (span.isRecording()) {
-            // If span is sampled in, add additional attributes
-
-            String tracingNamespace = getAzNamespace(context);
-            if (tracingNamespace != null) {
-                OpenTelemetryUtils.addAttribute(span, AZ_TRACING_NAMESPACE_KEY, tracingNamespace);
-            }
+        String tracingNamespace = getAzNamespace(context);
+        if (tracingNamespace != null) {
+            Attributes attributes
+                = OpenTelemetryUtils.convert(singletonMap(AZ_TRACING_NAMESPACE_KEY, tracingNamespace));
+            spanBuilder.setAllAttributes(attributes);
         }
 
+        Span span = spanBuilder.startSpan();
+
         return context.addData(PARENT_TRACE_CONTEXT_KEY,
             (traceContext != null ? traceContext : io.opentelemetry.context.Context.current()).with(span));
     }