Added pool of executors instead of spawning one threads.

gcloud-java-dns/src/main/java/com/google/gcloud/dns/testing/LocalDnsHelper.java

@@ -71,6 +71,7 @@
 import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -746,34 +747,20 @@ Response createChange(String projectId, String zoneName, Change change, String..
   }
 
   /**
-   * Applies change. Uses a new thread which applies the change only if DELAY_CHANGE is > 0.
+   * Applies change. Uses a different pooled thread which applies the change only if {@code
+   * delayChange} is > 0.
    */
-  private Thread invokeChange(final String projectId, final String zoneName,
+  private void invokeChange(final String projectId, final String zoneName,
       final String changeId) {
     if (delayChange > 0) {
-      EXECUTORS.scheduleWithFixedDelay(new Runnable() {
+      EXECUTORS.schedule(new Runnable() {
         @Override
         public void run() {
           applyExistingChange(projectId, zoneName, changeId);
         }
-      }, delayChange, )
-      Thread thread = new Thread() {
-        @Override
-        public void run() {
-          try {
-            Thread.sleep(delayChange); // simulate delayed execution
-          } catch (InterruptedException ex) {
-            log.log(Level.WARNING, "Thread was interrupted while sleeping.", ex);
-          }
-          // start applying the changes
-          applyExistingChange(projectId, zoneName, changeId);
-        }
-      };
-      thread.start();
-      return thread;
+      }, delayChange, TimeUnit.MILLISECONDS);
     } else {
       applyExistingChange(projectId, zoneName, changeId);
-      return null;
     }
   }