Do complex logic only when the FF is enabled

dd-trace-core/src/jmh/java/datadog/trace/api/naming/MessagingNamingBenchmark.java

@@ -0,0 +1,96 @@
+package datadog.trace.api.naming;
+
+import static java.util.concurrent.TimeUnit.MICROSECONDS;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+import datadog.trace.api.Config;
+import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
+import datadog.trace.core.BlackholeWriter;
+import datadog.trace.core.CoreTracer;
+import datadog.trace.core.TraceCounters;
+import java.util.WeakHashMap;
+import java.util.function.Supplier;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+/**
+ * Benchmark (pinThreadServiceName) Mode Cnt Score Error Units
+ * MessagingNamingBenchmark.complexSupplierServiceName false avgt 3 0.710 ± 0.040 us/op
+ * MessagingNamingBenchmark.complexSupplierServiceName true avgt 3 0.718 ± 0.105 us/op
+ * MessagingNamingBenchmark.constantServiceName false avgt 3 0.668 ± 0.024 us/op
+ * MessagingNamingBenchmark.constantSupplierServiceName false avgt 3 0.666 ± 0.044 us/op
+ */
+@State(Scope.Benchmark)
+@Warmup(iterations = 1, time = 15, timeUnit = SECONDS)
+@Measurement(iterations = 3, time = 30, timeUnit = SECONDS)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(MICROSECONDS)
+@Fork(value = 1)
+public class MessagingNamingBenchmark {
+
+  CoreTracer tracer;
+
+  WeakHashMap<ClassLoader, String> weakCache;
+
+  private static final Supplier<String> constantSupplier = () -> "constant";
+
+  private final Supplier<String> complexSupplier =
+      () -> {
+        String ret = weakCache.get(Thread.currentThread().getContextClassLoader());
+        if (ret == null) {
+          ret = Config.get().getServiceName();
+        }
+        return ret;
+      };
+
+  @Param({"false", "true"})
+  boolean pinThreadServiceName;
+
+  @Setup(Level.Iteration)
+  public void init(Blackhole blackhole) {
+    tracer =
+        CoreTracer.builder()
+            .writer(new BlackholeWriter(blackhole, new TraceCounters(), 0))
+            .strictTraceWrites(false)
+            .build();
+    weakCache = new WeakHashMap<>();
+    if (pinThreadServiceName) {
+      weakCache.put(Thread.currentThread().getContextClassLoader(), constantSupplier.get());
+    }
+  }
+
+  @Benchmark
+  public void constantServiceName(Blackhole blackhole) {
+    final AgentSpan span = tracer.startSpan("", "");
+    span.setServiceName("constant");
+    span.finish();
+    blackhole.consume(span);
+  }
+
+  @Benchmark
+  public void constantSupplierServiceName(Blackhole blackhole) {
+    final AgentSpan span = tracer.startSpan("", "");
+    span.setServiceName(constantSupplier.get());
+    span.finish();
+    blackhole.consume(span);
+  }
+
+  @Benchmark
+  public void complexSupplierServiceName(Blackhole blackhole) {
+    final AgentSpan span = tracer.startSpan("", "");
+    span.setServiceName(complexSupplier.get());
+    span.finish();
+    blackhole.consume(span);
+  }
+}

internal-api/src/main/java/datadog/trace/api/naming/v0/MessagingNamingV0.java

@@ -8,6 +8,23 @@
 import javax.annotation.Nonnull;
 
 class MessagingNamingV0 implements NamingSchema.ForMessaging {
+
+  private static class ClassloaderDependentNamingSupplier implements Supplier<String> {
+    private static final ClassloaderDependentNamingSupplier INSTANCE =
+        new ClassloaderDependentNamingSupplier();
+    private final String configServiceName = Config.get().getServiceName();
+
+    @Override
+    public String get() {
+      final String contextual = ClassloaderServiceNames.maybeGetForCurrentThread();
+      if (contextual != null) {
+        ServiceNameCollector.get().addService(contextual);
+        return contextual;
+      }
+      return configServiceName;
+    }
+  }
+
   private final boolean allowInferredServices;
 
   public MessagingNamingV0(final boolean allowInferredServices) {
@@ -48,20 +65,15 @@ public Supplier<String> inboundService(
     if (allowInferredServices) {
       if (useLegacyTracing) {
         ServiceNameCollector.get().addService(messagingSystem);
-        return () -> messagingSystem;
-      } else {
-        return () -> {
-          final String contextual = ClassloaderServiceNames.maybeGetForCurrentThread();
-          if (contextual != null) {
-            ServiceNameCollector.get().addService(contextual);
-            return contextual;
-          }
-          return Config.get().getServiceName();
-        };
+        return messagingSystem::toString;
+      } else if (Config.get().isJeeSplitByDeployment()) {
+        // in this particular case we're narrowing the service name from the context classloader.
+        // this is more expensive so we're doing only if that feature is enabled.
+        return ClassloaderDependentNamingSupplier.INSTANCE;
       }
-    } else {
-      return () -> null;
+      return Config.get()::getServiceName;
     }
+    return null;
   }
 
   @Override