Add a configuration option to vary how heavyweight anti-entropy is.

Change-Id: I57cea61182b3d19deb47608ffb7dd617529ae34c

@@ -98,6 +98,7 @@ public class EventuallyConsistentMapImpl<K, V>
     // TODO: Make these anti-entropy params configurable
     private long initialDelaySec = 5;
     private long periodSec = 5;
+    private boolean lightweightAntiEntropy = true;
 
     /**
      * Creates a new eventually consistent map shared amongst multiple instances.
@@ -567,35 +568,32 @@ public class EventuallyConsistentMapImpl<K, V>
 
     private void handleAntiEntropyAdvertisement(AntiEntropyAdvertisement<K> ad) {
         List<EventuallyConsistentMapEvent<K, V>> externalEvents;
-        boolean sync = false;
 
         externalEvents = antiEntropyCheckLocalItems(ad);
 
         antiEntropyCheckLocalRemoved(ad);
 
-        externalEvents.addAll(antiEntropyCheckRemoteRemoved(ad));
-
-        // if remote ad has something unknown, actively sync
-        for (K key : ad.timestamps().keySet()) {
-            if (!items.containsKey(key)) {
-                sync = true;
-                break;
-            }
-        }
+        if (!lightweightAntiEntropy) {
+            externalEvents.addAll(antiEntropyCheckRemoteRemoved(ad));
+
+            // if remote ad has something unknown, actively sync
+            for (K key : ad.timestamps().keySet()) {
+                if (!items.containsKey(key)) {
+                    // Send the advertisement back if this peer is out-of-sync
+                    final NodeId sender = ad.sender();
+                    AntiEntropyAdvertisement<K> myAd = createAdvertisement();
+                    try {
+                        unicastMessage(sender, antiEntropyAdvertisementSubject, myAd);
+                    } catch (IOException e) {
+                        log.debug(
+                                "Failed to send reactive anti-entropy advertisement to {}",
+                                sender);
+                    }
 
-        // Send the advertisement back if this peer is out-of-sync
-        if (sync) {
-            final NodeId sender = ad.sender();
-            AntiEntropyAdvertisement<K> myAd = createAdvertisement();
-            try {
-                unicastMessage(sender, antiEntropyAdvertisementSubject, myAd);
-            } catch (IOException e) {
-                log.debug(
-                        "Failed to send reactive anti-entropy advertisement to {}",
-                        sender);
+                    break;
+                }
             }
         }
-
         externalEvents.forEach(this::notifyListeners);
     }