Construct LettuceObservationContext with parent observation

After this commit, LettuceObservationContext.setParentObservation() is called right after Context rather than Observation created, then Context.getParentObservation() could be used in ObservationPredicate to determine whether Observation should be created.

Fix spring-projectsGH-2591

Author: quaff

src/main/java/org/springframework/data/redis/connection/lettuce/observability/MicrometerTracingAdapter.java

@@ -44,6 +44,7 @@
  * arguments will be captured in traces including these that may contain sensitive details.
  *
  * @author Mark Paluch
+ * @author Yanming Zhou
  * @since 3.0
  */
 public class MicrometerTracingAdapter implements Tracing {
@@ -121,24 +122,23 @@ public MicrometerTracer(ObservationRegistry observationRegistry) {
 
 		@Override
 		public Tracer.Span nextSpan() {
-			return this.postProcessSpan(createObservation());
+			return this.postProcessSpan(createObservation(null));
 		}
 
 		@Override
 		public Tracer.Span nextSpan(TraceContext traceContext) {
-
-			if (traceContext instanceof MicrometerTraceContext micrometerTraceContext) {
-
-				return micrometerTraceContext.observation == null ? nextSpan()
-						: postProcessSpan(createObservation().parentObservation(micrometerTraceContext.observation()));
-			}
-
-			return nextSpan();
+			return postProcessSpan(createObservation(traceContext));
 		}
 
-		private Observation createObservation() {
+		private Observation createObservation(@Nullable TraceContext traceContext) {
 			return RedisObservation.REDIS_COMMAND_OBSERVATION.observation(observationRegistry,
-					() -> new LettuceObservationContext(serviceName));
+					() -> {
+						LettuceObservationContext context = new LettuceObservationContext(serviceName);
+						if (traceContext instanceof MicrometerTraceContext micrometerTraceContext && micrometerTraceContext.observation != null) {
+							context.setParentObservation(micrometerTraceContext.observation);
+						}
+						return context;
+					});
 		}
 
 		private Tracer.Span postProcessSpan(Observation observation) {