DataDog · jordan-wong · Jul 14, 2026
@@ -1,36 +1,24 @@
+
 muzzle {
   pass {
     group = "io.reactivex.rxjava3"
     module = "rxjava"
     versions = "[3.0.0,)"
   }
-  // Assert the rxjava3 advice never resolves against rxjava2 — the two namespaces
-  // must not overlap. rxjava3 references io.reactivex.rxjava3.core.*, absent from the
-  // rxjava2 artifact, so muzzle must fail to match it.
-  fail {
-    name = "rxjava2-must-not-match"
-    group = "io.reactivex.rxjava2"
-    module = "rxjava"
-    versions = "[2.0.0,)"
-  }
 }
 
 apply from: "$rootDir/gradle/java.gradle"
 
 addTestSuiteForDir('latestDepTest', 'test')
 
 dependencies {
-  compileOnly group: 'org.reactivestreams', name: 'reactive-streams', version: '1.0.3'
+  compileOnly group: 'org.reactivestreams', name: 'reactive-streams', version: '1.0.0'
   compileOnly group: 'io.reactivex.rxjava3', name: 'rxjava', version: '3.0.0'
 
   testImplementation project(':dd-java-agent:instrumentation:datadog:tracing:trace-annotation')
   testImplementation project(':dd-java-agent:instrumentation:opentelemetry:opentelemetry-annotations-1.20')
+
   testImplementation group: 'io.reactivex.rxjava3', name: 'rxjava', version: '3.0.0'
   testImplementation group: 'io.opentelemetry.instrumentation', name: 'opentelemetry-instrumentation-annotations', version: '1.28.0'
-
-  // Load the rxjava2 instrumenter at test runtime to prove the two versions coexist on
-  // the agent without interference (it stays dormant with only rxjava3 on the classpath).
-  testRuntimeOnly project(':dd-java-agent:instrumentation:rxjava:rxjava-2.0')
-
-  latestDepTestImplementation group: 'io.reactivex.rxjava3', name: 'rxjava', version: '+'
+  latestDepTestImplementation group: 'io.reactivex.rxjava3', name: 'rxjava', version: '3.+'
 }
@@ -18,7 +18,6 @@
 
 public final class CompletableInstrumentation
     implements Instrumenter.ForSingleType, Instrumenter.HasMethodAdvice {
-
   @Override
   public String instrumentedType() {
     return "io.reactivex.rxjava3.core.Completable";
@@ -55,6 +54,7 @@ public static ContextScope onSubscribe(
         Context parentContext =
             InstrumentationContext.get(Completable.class, Context.class).get(completable);
         if (parentContext != null) {
+          // wrap the observer so spans from its events treat the captured span as their parent
           observer = new TracingCompletableObserver(observer, parentContext);
           // attach the context here in case additional observers are created during subscribe
           return parentContext.attach();

@@ -18,7 +18,6 @@
 
 public final class FlowableInstrumentation
     implements Instrumenter.ForSingleType, Instrumenter.HasMethodAdvice {
-
   @Override
   public String instrumentedType() {
     return "io.reactivex.rxjava3.core.Flowable";
@@ -54,6 +53,7 @@ public static ContextScope onSubscribe(
         Context parentContext =
             InstrumentationContext.get(Flowable.class, Context.class).get(flowable);
         if (parentContext != null) {
+          // wrap the subscriber so spans from its events treat the captured span as their parent
           subscriber = new TracingSubscriber<>(subscriber, parentContext);
           // attach the context here in case additional subscribers are created during subscribe
           return parentContext.attach();

@@ -52,6 +52,7 @@ public static ContextScope onSubscribe(
       if (observer != null) {
         Context parentContext = InstrumentationContext.get(Maybe.class, Context.class).get(maybe);
         if (parentContext != null) {
+          // wrap the observer so spans from its events treat the captured span as their parent
           observer = new TracingMaybeObserver<>(observer, parentContext);
           // attach the context here in case additional observers are created during subscribe
           return parentContext.attach();

@@ -53,6 +53,7 @@ public static ContextScope onSubscribe(
         Context parentContext =
             InstrumentationContext.get(Observable.class, Context.class).get(observable);
         if (parentContext != null) {
+          // wrap the observer so spans from its events treat the captured span as their parent
           observer = new TracingObserver<>(observer, parentContext);
           // attach the context here in case additional observers are created during subscribe
           return parentContext.attach();

@@ -13,40 +13,39 @@
 @AutoService(InstrumenterModule.class)
 public final class RxJavaModule extends InstrumenterModule.ContextTracking {
   public RxJavaModule() {
-    super("rxjava", "rxjava-3");
+    super("rxjava");
   }
 
   @Override
   public String[] helperClassNames() {
     return new String[] {
-      packageName + ".TracingCompletableObserver",
+      packageName + ".TracingObserver",
       packageName + ".TracingSubscriber",
+      packageName + ".TracingSingleObserver",
       packageName + ".TracingMaybeObserver",
-      packageName + ".TracingObserver",
+      packageName + ".TracingCompletableObserver",
       packageName + ".RxJavaAsyncResultExtension",
-      packageName + ".TracingSingleObserver",
     };
   }
 
   @Override
   public Map<String, String> contextStore() {
-    String contextClass = Context.class.getName();
     final Map<String, String> store = new HashMap<>();
-    store.put("io.reactivex.rxjava3.core.Flowable", contextClass);
-    store.put("io.reactivex.rxjava3.core.Completable", contextClass);
-    store.put("io.reactivex.rxjava3.core.Maybe", contextClass);
-    store.put("io.reactivex.rxjava3.core.Observable", contextClass);
-    store.put("io.reactivex.rxjava3.core.Single", contextClass);
+    store.put("io.reactivex.rxjava3.core.Observable", Context.class.getName());
+    store.put("io.reactivex.rxjava3.core.Flowable", Context.class.getName());
+    store.put("io.reactivex.rxjava3.core.Single", Context.class.getName());
+    store.put("io.reactivex.rxjava3.core.Maybe", Context.class.getName());
+    store.put("io.reactivex.rxjava3.core.Completable", Context.class.getName());
     return store;
   }
 
   @Override
   public List<Instrumenter> typeInstrumentations() {
     return asList(
-        new CompletableInstrumentation(),
+        new ObservableInstrumentation(),
         new FlowableInstrumentation(),
+        new SingleInstrumentation(),
         new MaybeInstrumentation(),
-        new ObservableInstrumentation(),
-        new SingleInstrumentation());
+        new CompletableInstrumentation());
   }
 }