Simplifying approach - just use final field in constructor

Author: dougqh

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/BaseDecorator.java

@@ -46,8 +46,7 @@ public String apply(Class<?> clazz) {
 
   private final TagMap.Entry traceAnalyticsEntry;
 
-  // Deliberately not volatile, reading null and repeating the calculation is safe
-  private TagMap.Entry cachedComponentEntry = null;
+  protected final TagMap.Entry componentEntry;
 
   protected BaseDecorator() {
     final Config config = Config.get();
@@ -65,6 +64,8 @@ protected BaseDecorator() {
         this.traceAnalyticsEnabled
             ? TagMap.Entry.create(DDTags.ANALYTICS_SAMPLE_RATE, traceAnalyticsSampleRate)
             : null;
+    
+    this.componentEntry = TagMap.Entry.create(Tags.COMPONENT, component());
   }
 
   protected abstract String[] instrumentationNames();
@@ -73,15 +74,6 @@ protected BaseDecorator() {
 
   protected abstract CharSequence component();
 
-  /** Caches the component TagMap.Entry, so it isn't recreated for every trace */
-  protected final TagMap.Entry componentEntry() {
-    TagMap.Entry componentEntry = cachedComponentEntry;
-    if (componentEntry == null) {
-      cachedComponentEntry = componentEntry = TagMap.Entry.create(Tags.COMPONENT, component());
-    }
-    return componentEntry;
-  }
-
   protected boolean traceAnalyticsDefault() {
     return false;
   }
@@ -90,11 +82,9 @@ public AgentSpan afterStart(final AgentSpan span) {
     if (spanType() != null) {
       span.setSpanType(spanType());
     }
+    
+    span.setTag(componentEntry);
 
-    span.setTag(componentEntry());
-
-    // DQH - Could retrieve the value from componentEntry and cast to avoid the virtual call,
-    // unclear which option is better here
     final CharSequence component = component();
     span.context().setIntegrationName(component);