add SdkTracerProvider.setScopeConfigurator() and support

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkTracer.java

@@ -30,9 +30,8 @@ class SdkTracer implements Tracer {
 
   private final TracerSharedState sharedState;
   private final InstrumentationScopeInfo instrumentationScopeInfo;
-
-  // TODO: add dedicated API for updating scope config.
-  @SuppressWarnings("FieldCanBeFinal") // For now, allow updating reflectively.
+  // deliberately not volatile because of performance concerns
+  // - which means its eventually consistent
   private boolean tracerEnabled;
 
   SdkTracer(
@@ -79,4 +78,14 @@ public SpanBuilder spanBuilder(String spanName) {
   InstrumentationScopeInfo getInstrumentationScopeInfo() {
     return instrumentationScopeInfo;
   }
+
+  // Visible for testing
+  boolean isEnabled() {
+    return tracerEnabled;
+  }
+
+  // currently not public as experimental
+  void updateTracerConfig(TracerConfig tracerConfig) {
+    this.tracerEnabled = tracerConfig.isEnabled();
+  }
 }

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkTracerProvider.java

@@ -30,7 +30,9 @@ public final class SdkTracerProvider implements TracerProvider, Closeable {
   static final String DEFAULT_TRACER_NAME = "";
   private final TracerSharedState sharedState;
   private final ComponentRegistry<SdkTracer> tracerSdkComponentRegistry;
-  private final ScopeConfigurator<TracerConfig> tracerConfigurator;
+  // deliberately not volatile because of performance concerns
+  // - which means its eventually consistent
+  private ScopeConfigurator<TracerConfig> tracerConfigurator;
 
   /**
    * Returns a new {@link SdkTracerProviderBuilder} for {@link SdkTracerProvider}.
@@ -100,6 +102,17 @@ public Sampler getSampler() {
     return sharedState.getSampler();
   }
 
+  // currently not public as experimental
+  void setScopeConfigurator(ScopeConfigurator<TracerConfig> scopeConfigurator) {
+    this.tracerConfigurator = scopeConfigurator;
+    this.tracerSdkComponentRegistry
+        .getComponents()
+        .forEach(
+            sdkTracer ->
+                sdkTracer.updateTracerConfig(
+                    getTracerConfig(sdkTracer.getInstrumentationScopeInfo())));
+  }
+
   /**
    * Attempts to stop all the activity for {@link Tracer}s created by this provider. Calls {@link
    * SpanProcessor#shutdown()} for all registered {@link SpanProcessor}s.

sdk/trace/src/test/java/io/opentelemetry/sdk/trace/SdkTracerProviderTest.java

@@ -18,7 +18,9 @@
 import io.opentelemetry.sdk.common.Clock;
 import io.opentelemetry.sdk.common.CompletableResultCode;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
+import io.opentelemetry.sdk.internal.ScopeConfigurator;
 import io.opentelemetry.sdk.resources.Resource;
+import io.opentelemetry.sdk.trace.internal.TracerConfig;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
 import java.util.function.Supplier;
 import org.junit.jupiter.api.BeforeEach;
@@ -184,6 +186,22 @@ void propagatesInstrumentationScopeInfoToTracer() {
     assertThat(((SdkTracer) tracer).getInstrumentationScopeInfo()).isEqualTo(expected);
   }
 
+  @Test
+  void propagatesEnablementToTracer() {
+    SdkTracer tracer = (SdkTracer) tracerFactory.get("test");
+    boolean isEnabled = tracer.isEnabled();
+    ScopeConfigurator<TracerConfig> flipConfigurator =
+        new ScopeConfigurator<TracerConfig>() {
+          @Override
+          public TracerConfig apply(InstrumentationScopeInfo scopeInfo) {
+            return isEnabled ? TracerConfig.disabled() : TracerConfig.enabled();
+          }
+        };
+    // all in the same thread, so should see enablement change immediately
+    tracerFactory.setScopeConfigurator(flipConfigurator);
+    assertThat(tracer.isEnabled()).isEqualTo(!isEnabled);
+  }
+
   @Test
   void build_SpanLimits() {
     SpanLimits initialSpanLimits = SpanLimits.builder().build();

sdk/trace/src/test/java/io/opentelemetry/sdk/trace/SdkTracerTest.java

@@ -16,6 +16,7 @@
 import io.opentelemetry.sdk.trace.data.SpanData;
 import io.opentelemetry.sdk.trace.export.BatchSpanProcessor;
 import io.opentelemetry.sdk.trace.export.SpanExporter;
+import io.opentelemetry.sdk.trace.internal.TracerConfig;
 import java.util.Collection;
 import java.util.concurrent.atomic.AtomicLong;
 import org.junit.jupiter.api.Test;
@@ -50,6 +51,14 @@ void getInstrumentationScopeInfo() {
     assertThat(tracer.getInstrumentationScopeInfo()).isEqualTo(instrumentationScopeInfo);
   }
 
+  @Test
+  void updateEnabled() {
+    tracer.updateTracerConfig(TracerConfig.disabled());
+    assertThat(tracer.isEnabled()).isFalse();
+    tracer.updateTracerConfig(TracerConfig.enabled());
+    assertThat(tracer.isEnabled()).isTrue();
+  }
+
   @Test
   void propagatesInstrumentationScopeInfoToSpan() {
     ReadableSpan readableSpan = (ReadableSpan) tracer.spanBuilder("spanName").startSpan();