Disable decorators via config

dd-trace-api/src/main/java/datadog/trace/api/Config.java

@@ -596,6 +596,10 @@ public class Config {
     return jmxFetchIntegrationEnabled(integrationNames, defaultEnabled);
   }
 
+  public boolean isDecoratorEnabled(final String name) {
+    return getBooleanSettingFromEnvironment("trace." + name.toLowerCase() + ".enabled", true);
+  }
+
   /**
    * @deprecated This method should only be used internally. Use the instance getter instead {@link
    *     #isJmxFetchIntegrationEnabled(SortedSet, boolean)}.

dd-trace-ot/src/main/java/datadog/opentracing/decorators/DDDecoratorsFactory.java

@@ -4,31 +4,44 @@ import datadog.trace.api.Config;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import lombok.extern.slf4j.Slf4j;
 
 /** Create DDSpanDecorators */
+@Slf4j
 public class DDDecoratorsFactory {
   public static List<AbstractDecorator> createBuiltinDecorators() {
 
-    final List<AbstractDecorator> decorators =
+    final List<AbstractDecorator> decorators = new ArrayList<>();
-        new ArrayList<>(
-            Arrays.asList(
-                new AnalyticsSampleRateDecorator(),
-                new DBStatementAsResourceName(),
-                new DBTypeDecorator(),
-                new ErrorFlag(),
-                new ForceManualDropDecorator(),
-                new ForceManualKeepDecorator(),
-                new OperationDecorator(),
-                new PeerServiceDecorator(),
-                new ResourceNameDecorator(),
-                new ServiceNameDecorator(),
-                new ServiceNameDecorator("service", false),
-                new ServletContextDecorator(),
-                new SpanTypeDecorator(),
-                new Status404Decorator(),
-                new Status5XXDecorator(),
-                new URLAsResourceName()));
 
+    for (final AbstractDecorator decorator :
+        Arrays.asList(
+            new AnalyticsSampleRateDecorator(),
+            new DBStatementAsResourceName(),
+            new DBTypeDecorator(),
+            new ErrorFlag(),
+            new ForceManualDropDecorator(),
+            new ForceManualKeepDecorator(),
+            new OperationDecorator(),
+            new PeerServiceDecorator(),
+            new ResourceNameDecorator(),
+            new ServiceNameDecorator(),
+            new ServiceNameDecorator("service", false),
+            new ServletContextDecorator(),
+            new SpanTypeDecorator(),
+            new Status404Decorator(),
+            new Status5XXDecorator(),
+            new URLAsResourceName())) {
+
+      if (Config.get().isDecoratorEnabled(decorator.getClass().getSimpleName())) {
+        decorators.add(decorator);
+      } else {
+        log.debug("{} disabled", decorator.getClass().getSimpleName());
+      }
+    }
+
+    // SplitByTags purposely does not check for ServiceNameDecorator being enabled
+    // This allows for ServiceNameDecorator to be disabled above while keeping SplitByTags
+    // SplitByTags can be disable by removing SplitByTags config
     for (final String splitByTag : Config.get().getSplitByTags()) {
       decorators.add(new ServiceNameDecorator(splitByTag, true));
     }

dd-trace-ot/src/test/groovy/datadog/opentracing/decorators/SpanDecoratorTest.groovy

@@ -470,4 +470,72 @@ class SpanDecoratorTest extends DDSpecification {
     then:
     span.resourceName == "some-statement"
   }
+
+  def "disable decorator via config"() {
+    setup:
+    ConfigUtils.updateConfig {
+      System.setProperty("dd.trace." + PeerServiceDecorator.getSimpleName().toLowerCase() + ".enabled", "false")
+    }
+
+    tracer = new DDTracer(
+      "some-service",
+      new LoggingWriter(),
+      new AllSampler(),
+      "some-runtime-id",
+      emptyMap(),
+      emptyMap(),
+      emptyMap(),
+      emptyMap()
+    )
+
+    when:
+    def span = tracer.buildSpan("some span").withTag(Tags.PEER_SERVICE.key, "peer-service").start()
+    span.finish()
+
+    then:
+    span.getServiceName() == "some-service"
+
+    cleanup:
+    ConfigUtils.updateConfig {
+      System.clearProperty("dd.trace." + PeerServiceDecorator.getSimpleName().toLowerCase() + ".enabled")
+    }
+  }
+
+  def "disabling service decorator does not disable split by tags"() {
+    setup:
+    ConfigUtils.updateConfig {
+      System.setProperty("dd.trace." + ServiceNameDecorator.getSimpleName().toLowerCase() + ".enabled", "false")
+    }
+
+    tracer = new DDTracer(
+      "some-service",
+      new LoggingWriter(),
+      new AllSampler(),
+      "some-runtime-id",
+      emptyMap(),
+      emptyMap(),
+      emptyMap(),
+      emptyMap()
+    )
+
+    when:
+    def span = tracer.buildSpan("some span").withTag(tag, name).start()
+    span.finish()
+
+    then:
+    span.getServiceName() == expected
+
+    cleanup:
+    ConfigUtils.updateConfig {
+      System.clearProperty("dd.trace." + ServiceNameDecorator.getSimpleName().toLowerCase() + ".enabled")
+    }
+
+    where:
+    tag                 | name          | expected
+    DDTags.SERVICE_NAME | "new-service" | "some-service"
+    "service"           | "new-service" | "some-service"
+    "sn.tag1"           | "new-service" | "new-service"
+
+
+  }
 }