Improvements due to the review

dd-trace/src/main/java/com/datadoghq/trace/writer/DDAgentWriter.java

@@ -38,7 +38,7 @@ public class DDAgentWriter implements Writer {
   /** Flush interval for the API in seconds */
   private static final long FLUSH_TIME_SECONDS = 1;
 
-  /** Scheduled thread pool, it' acting like a cron */
+  /** Scheduled thread pool, acting like a cron */
   private final ScheduledExecutorService scheduledExecutor = Executors.newScheduledThreadPool(1);
 
   /** Effective thread pool, where real logic is done */
@@ -70,7 +70,7 @@ public class DDAgentWriter implements Writer {
 
     final List<DDBaseSpan<?>> removed = traces.add(trace);
     if (removed != null && !queueFullReported) {
-      log.warn("Queue is full, dropping one trace, queue size: {}", DEFAULT_MAX_TRACES);
+      log.debug("Queue is full, traces will be discarded, queue size: {}", DEFAULT_MAX_TRACES);
       queueFullReported = true;
       return;
     }
@@ -107,7 +107,7 @@ public class DDAgentWriter implements Writer {
   }
 
   /** Infinite tasks blocking until some spans come in the blocking queue. */
-  private class TracesSendingTask implements Runnable {
+  class TracesSendingTask implements Runnable {
 
     @Override
     public void run() {
@@ -122,8 +122,6 @@ public class DDAgentWriter implements Writer {
       }
     }
 
-    public void size() {}
-
     class SendingTask implements Callable<Long> {
 
       @Override

dd-trace/src/main/java/com/datadoghq/trace/writer/WriterQueue.java

@@ -1,7 +1,6 @@
 package com.datadoghq.trace.writer;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.ThreadLocalRandom;
 
@@ -21,7 +20,6 @@ class WriterQueue<T> {
 
   private final int capacity;
   private volatile ArrayList<T> list;
-  private volatile int elementCount = 0;
 
   /**
    * Default construct, a capacity must be provided
@@ -32,7 +30,7 @@ class WriterQueue<T> {
     if (capacity < 1) {
       throw new IllegalArgumentException("Capacity couldn't be 0");
     }
-    list = new ArrayList<>(capacity);
+    this.list = emptyList(capacity);
     this.capacity = capacity;
   }
 
@@ -43,10 +41,8 @@ class WriterQueue<T> {
    * @return a list contain all elements
    */
   public synchronized List<T> getAll() {
-    List<T> all = Collections.emptyList();
+    final List<T> all = list;
-    all = list;
+    list = emptyList(capacity);
-    list = new ArrayList<>(capacity);
-    elementCount = 0;
     return all;
   }
 
@@ -60,11 +56,10 @@ class WriterQueue<T> {
   public synchronized T add(final T element) {
 
     T removed = null;
-    if (elementCount < capacity) {
+    if (list.size() < capacity) {
       list.add(element);
-      ++elementCount;
     } else {
-      final int index = ThreadLocalRandom.current().nextInt(0, elementCount);
+      final int index = ThreadLocalRandom.current().nextInt(0, list.size());
       removed = list.set(index, element);
     }
     return removed;
@@ -78,7 +73,7 @@ class WriterQueue<T> {
    * @return the current size of the queue
    */
   public int size() {
-    return elementCount;
+    return list.size();
   }
 
   /**
@@ -87,6 +82,10 @@ class WriterQueue<T> {
    * @return true if the queue is empty
    */
   public boolean isEmpty() {
-    return elementCount == 0;
+    return list.isEmpty();
+  }
+
+  private ArrayList<T> emptyList(final int capacity) {
+    return new ArrayList<>(capacity);
   }
 }