feat(core): Refactor action elements

Author: PerfectSlayer

dd-trace-core/src/main/java/datadog/trace/core/PendingTraceBuffer.java

@@ -55,6 +55,8 @@ private static class DelayingPendingTraceBuffer extends PendingTraceBuffer {
     private static final long FORCE_SEND_DELAY_MS = TimeUnit.SECONDS.toMillis(5);
     private static final long SEND_DELAY_NS = TimeUnit.MILLISECONDS.toNanos(500);
     private static final long SLEEP_TIME_MS = 100;
+    private static final CommandElement FLUSH_ELEMENT = new CommandElement();
+    private static final CommandElement DUMP_ELEMENT = new CommandElement();
 
     private final MpscBlockingConsumerArrayQueue<Element> queue;
     private final Thread worker;
@@ -118,10 +120,10 @@ public void flush() {
       if (worker.isAlive()) {
         int count = flushCounter.get();
         int loop = 1;
-        boolean signaled = queue.offer(FlushElement.FLUSH_ELEMENT);
+        boolean signaled = queue.offer(FLUSH_ELEMENT);
         while (!closed && !signaled) {
           yieldOrSleep(loop++);
-          signaled = queue.offer(FlushElement.FLUSH_ELEMENT);
+          signaled = queue.offer(FLUSH_ELEMENT);
         }
         int newCount = flushCounter.get();
         while (!closed && count >= newCount) {
@@ -161,41 +163,7 @@ public Element get() {
       }
     }
 
-    private static final class FlushElement implements Element {
-      static FlushElement FLUSH_ELEMENT = new FlushElement();
-
-      @Override
-      public long oldestFinishedTime() {
-        return 0;
-      }
-
-      @Override
-      public boolean lastReferencedNanosAgo(long nanos) {
-        return false;
-      }
-
-      @Override
-      public void write() {}
-
-      @Override
-      public DDSpan getRootSpan() {
-        return null;
-      }
-
-      @Override
-      public boolean setEnqueued(boolean enqueued) {
-        return true;
-      }
-
-      @Override
-      public boolean writeOnBufferFull() {
-        return true;
-      }
-    }
-
-    private static final class DumpElement implements Element {
-      static DumpElement DUMP_ELEMENT = new DumpElement();
-
+    private static final class CommandElement implements Element {
       @Override
       public long oldestFinishedTime() {
         return 0;
@@ -243,14 +211,14 @@ public void run() {
               pendingTrace = queue.take(); // block until available;
             }
 
-            if (pendingTrace instanceof FlushElement) {
+            if (pendingTrace == FLUSH_ELEMENT) {
               // Since this is an MPSC queue, the drain needs to be called on the consumer thread
               queue.drain(WriteDrain.WRITE_DRAIN);
               flushCounter.incrementAndGet();
               continue;
             }
 
-            if (pendingTrace instanceof DumpElement) {
+            if (pendingTrace == DUMP_ELEMENT) {
               queue.drain(DumpDrain.DUMP_DRAIN);
               queue.fill(DumpDrain.DUMP_DRAIN, DumpDrain.DATA.size());
               dumpCounter.incrementAndGet();
@@ -364,10 +332,10 @@ public void prepareForFlare() {
       if (buffer.worker.isAlive()) {
         int count = buffer.dumpCounter.get();
         int loop = 1;
-        boolean signaled = buffer.queue.offer(DelayingPendingTraceBuffer.DumpElement.DUMP_ELEMENT);
+        boolean signaled = buffer.queue.offer(DelayingPendingTraceBuffer.DUMP_ELEMENT);
         while (!buffer.closed && !signaled) {
           buffer.yieldOrSleep(loop++);
-          signaled = buffer.queue.offer(DelayingPendingTraceBuffer.DumpElement.DUMP_ELEMENT);
+          signaled = buffer.queue.offer(DelayingPendingTraceBuffer.DUMP_ELEMENT);
         }
         int newCount = buffer.dumpCounter.get();
         while (!buffer.closed && count >= newCount) {