Add GlobalOpenTelemetry#isSet

Author: jack-berg

api/all/src/main/java/io/opentelemetry/api/GlobalOpenTelemetry.java

@@ -18,6 +18,7 @@
 import io.opentelemetry.context.propagation.ContextPropagators;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.Objects;
 import java.util.function.Supplier;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -85,7 +86,7 @@ public static OpenTelemetry get() {
           }
 
           set(OpenTelemetry.noop());
-          return OpenTelemetry.noop();
+          openTelemetry = Objects.requireNonNull(globalOpenTelemetry);
         }
       }
     }
@@ -133,6 +134,20 @@ public static void set(Supplier<OpenTelemetry> supplier) {
     }
   }
 
+  /**
+   * Evaluate if the global instance has been set without the side effects of {@link #get()}.
+   *
+   * <p>This is useful for evaluating if any code, like the OpenTelemetry javaagent, has previously
+   * set the global instance while preserving the ability to set it.
+   *
+   * @return true if the global instance has been set, false otherwise.
+   */
+  public static boolean isSet() {
+    synchronized (mutex) {
+      return globalOpenTelemetry != null;
+    }
+  }
+
   /** Returns the globally registered {@link TracerProvider}. */
   public static TracerProvider getTracerProvider() {
     return get().getTracerProvider();

api/testing-internal/src/main/java/io/opentelemetry/api/testing/internal/AbstractOpenTelemetryTest.java

@@ -31,10 +31,6 @@ private void setOpenTelemetry() {
     GlobalOpenTelemetry.set(getOpenTelemetry());
   }
 
-  private static OpenTelemetry getGlobalOpenTelemetry() {
-    return GlobalOpenTelemetry.get();
-  }
-
   @AfterEach
   public void after() {
     GlobalOpenTelemetry.resetForTest();
@@ -90,7 +86,9 @@ void independentNonGlobalPropagators() {
 
   @Test
   void setThenSet() {
+    assertThat(GlobalOpenTelemetry.isSet()).isFalse();
     setOpenTelemetry();
+    assertThat(GlobalOpenTelemetry.isSet()).isTrue();
     assertThatThrownBy(() -> GlobalOpenTelemetry.set(getOpenTelemetry()))
         .isInstanceOf(IllegalStateException.class)
         .hasMessageContaining("GlobalOpenTelemetry.set has already been called")
@@ -99,14 +97,29 @@ void setThenSet() {
 
   @Test
   void getThenSet() {
-    assertThat(getGlobalOpenTelemetry().getClass().getName())
-        .isEqualTo("io.opentelemetry.api.DefaultOpenTelemetry");
+    assertThat(GlobalOpenTelemetry.isSet()).isFalse();
+    // Calling GlobalOpenTelemetry.get() has the side affect of setting GlobalOpenTelemetry to an
+    // (obfuscated) noop.
+    // Call GlobalOpenTelemetry.get() using a utility method so we can later assert it was
+    // responsible for setting GlobalOpenTelemetry.
+    assertThat(getGlobalOpenTelemetry())
+        .satisfies(
+            instance ->
+                assertThat(instance.getClass().getName())
+                    .isEqualTo("io.opentelemetry.api.GlobalOpenTelemetry$ObfuscatedOpenTelemetry"))
+        .extracting("delegate")
+        .isSameAs(OpenTelemetry.noop());
+    assertThat(GlobalOpenTelemetry.isSet()).isTrue();
     assertThatThrownBy(() -> GlobalOpenTelemetry.set(getOpenTelemetry()))
         .isInstanceOf(IllegalStateException.class)
         .hasMessageContaining("GlobalOpenTelemetry.set has already been called")
         .hasStackTraceContaining("getGlobalOpenTelemetry");
   }
 
+  private static OpenTelemetry getGlobalOpenTelemetry() {
+    return GlobalOpenTelemetry.get();
+  }
+
   @Test
   void toString_noop_Valid() {
     assertThat(getOpenTelemetry().toString())

docs/apidiffs/current_vs_latest/opentelemetry-api.txt

@@ -1,2 +1,4 @@
 Comparing source compatibility of opentelemetry-api-1.56.0-SNAPSHOT.jar against opentelemetry-api-1.55.0.jar
-No changes.
+***  MODIFIED CLASS: PUBLIC FINAL io.opentelemetry.api.GlobalOpenTelemetry  (not serializable)
+	===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
+	+++  NEW METHOD: PUBLIC(+) STATIC(+) boolean isSet()

sdk-extensions/autoconfigure/src/testFullConfig/java/io/opentelemetry/sdk/autoconfigure/AutoConfiguredOpenTelemetrySdkTest.java

@@ -73,7 +73,7 @@ void initializeAndGet_noGlobal() {
   @Test
   void globalOpenTelemetry_AutoConfigureDisabled() {
     // Autoconfigure is disabled by default and enabled via otel.java.global-autoconfigure.enabled
-    assertThat(GlobalOpenTelemetry.get()).isSameAs(OpenTelemetry.noop());
+    assertThat(GlobalOpenTelemetry.get()).extracting("delegate").isSameAs(OpenTelemetry.noop());
 
     logs.assertContains(
         "AutoConfiguredOpenTelemetrySdk found on classpath but automatic configuration is disabled."

sdk/testing/src/test/java/io/opentelemetry/sdk/testing/junit5/OpenTelemetryExtensionTest.java

@@ -230,7 +230,7 @@ void afterAll() {
     assertThat(extension.getSpans()).isNotEmpty();
 
     extension.afterAll(null);
-    assertThat(GlobalOpenTelemetry.get()).isSameAs(OpenTelemetry.noop());
+    assertThat(GlobalOpenTelemetry.get()).extracting("delegate").isSameAs(OpenTelemetry.noop());
 
     meter.counterBuilder("counter").build().add(10);
     tracer.spanBuilder("span").startSpan().end();