GOSSIP-65 Implement crdt LWW-Element-Set

LWWSet implemented + se/de + unit tests + jackson tests + DataTests

gossip-base/src/main/java/org/apache/gossip/crdt/CrdtModule.java

@@ -35,6 +35,19 @@ abstract class OrSetMixin<E> {
   @JsonIgnore abstract boolean isEmpty();
 }
 
+abstract class LWWSetMixin<ElementType> {
+  @JsonCreator
+  LWWSetMixin(@JsonProperty("data") Map<ElementType, LWWSet.Timestamps> struct) { }
+  @JsonProperty("data") abstract Map<ElementType, LWWSet.Timestamps> getStruct();
+}
+
+abstract class LWWSetTimestampsMixin {
+  @JsonCreator
+  LWWSetTimestampsMixin(@JsonProperty("add") long latestAdd, @JsonProperty("remove") long latestRemove) { }
+  @JsonProperty("add") abstract long getLatestAdd();
+  @JsonProperty("remove") abstract long getLatestRemove();
+}
+
 abstract class GrowOnlySetMixin<E>{
   @JsonCreator
   GrowOnlySetMixin(@JsonProperty("elements") Set<E> elements){ }
@@ -63,6 +76,8 @@ public class CrdtModule extends SimpleModule {
     context.setMixInAnnotations(OrSet.class, OrSetMixin.class);
     context.setMixInAnnotations(GrowOnlySet.class, GrowOnlySetMixin.class);
     context.setMixInAnnotations(GrowOnlyCounter.class, GrowOnlyCounterMixin.class);
+    context.setMixInAnnotations(LWWSet.class, LWWSetMixin.class);
+    context.setMixInAnnotations(LWWSet.Timestamps.class, LWWSetTimestampsMixin.class);
   }
 
 }

gossip-base/src/main/java/org/apache/gossip/crdt/LWWSet.java

@@ -0,0 +1,152 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gossip.crdt;
+
+import org.apache.gossip.manager.Clock;
+import org.apache.gossip.manager.SystemClock;
+
+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class LWWSet<ElementType> implements CrdtSet<ElementType, Set<ElementType>, LWWSet<ElementType>> {
+  static private Clock clock = new SystemClock();
+
+  private final Map<ElementType, Timestamps> struct;
+
+  static class Timestamps {
+    private final long latestAdd;
+    private final long latestRemove;
+
+    Timestamps(){
+      latestAdd = 0;
+      latestRemove = 0;
+    }
+
+    Timestamps(long add, long remove){
+      latestAdd = add;
+      latestRemove = remove;
+    }
+
+    long getLatestAdd() {
+      return latestAdd;
+    }
+
+    long getLatestRemove() {
+      return latestRemove;
+    }
+
+    // consider element present when addTime >= removeTime, so we prefer add to remove
+    boolean isPresent(){
+      return latestAdd >= latestRemove;
+    }
+
+    Timestamps updateAdd(){
+      return new Timestamps(clock.nanoTime(), latestRemove);
+    }
+
+    Timestamps updateRemove(){
+      return new Timestamps(latestAdd, clock.nanoTime());
+    }
+
+    Timestamps merge(Timestamps other){
+      if (other == null){
+        return this;
+      }
+      return new Timestamps(Math.max(latestAdd, other.latestAdd), Math.max(latestRemove, other.latestRemove));
+    }
+  }
+
+
+  public LWWSet(){
+    struct = new HashMap<>();
+  }
+
+  @SafeVarargs
+  public LWWSet(ElementType... elements){
+    this(new HashSet<>(Arrays.asList(elements)));
+  }
+
+  public LWWSet(Set<ElementType> set){
+    struct = new HashMap<>();
+    for (ElementType e : set){
+      struct.put(e, new Timestamps().updateAdd());
+    }
+  }
+
+  public LWWSet(LWWSet<ElementType> first, LWWSet<ElementType> second){
+    Function<ElementType, Timestamps> timestampsFor = p -> {
+      Timestamps firstTs = first.struct.get(p);
+      Timestamps secondTs = second.struct.get(p);
+      if (firstTs == null){
+        return secondTs;
+      }
+      return firstTs.merge(secondTs);
+    };
+    struct = Stream.concat(first.struct.keySet().stream(), second.struct.keySet().stream())
+        .distinct().collect(Collectors.toMap(p -> p, timestampsFor));
+  }
+
+  public LWWSet<ElementType> add(ElementType e){
+    return this.merge(new LWWSet<>(e));
+  }
+
+  // for serialization
+  LWWSet(Map<ElementType, Timestamps> struct){
+    this.struct = struct;
+  }
+
+  Map<ElementType, Timestamps> getStruct() {
+    return struct;
+  }
+
+
+  public LWWSet<ElementType> remove(ElementType e){
+    Timestamps eTimestamps = struct.get(e);
+    if (eTimestamps == null || !eTimestamps.isPresent()){
+      return this;
+    }
+    Map<ElementType, Timestamps> changeMap = new HashMap<>();
+    changeMap.put(e, eTimestamps.updateRemove());
+    return this.merge(new LWWSet<>(changeMap));
+  }
+
+  @Override
+  public LWWSet<ElementType> merge(LWWSet<ElementType> other){
+    return new LWWSet<>(this, other);
+  }
+
+  @Override
+  public Set<ElementType> value(){
+    return struct.entrySet().stream()
+        .filter(entry -> entry.getValue().isPresent())
+        .map(Map.Entry::getKey)
+        .collect(Collectors.toSet());
+  }
+
+  @Override
+  public LWWSet<ElementType> optimize(){
+    return this;
+  }
+
+  @Override
+  public boolean equals(Object obj){
+    return this == obj || (obj != null && getClass() == obj.getClass() && value().equals(((LWWSet) obj).value()));
+  }
+}

gossip-base/src/test/java/org/apache/gossip/crdt/LWWSetTest.java

@@ -0,0 +1,155 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gossip.crdt;
+
+import org.apache.gossip.manager.Clock;
+import org.apache.gossip.manager.SystemClock;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class LWWSetTest {
+  static private Clock clock = new SystemClock();
+  private Set<Integer> sampleSet;
+
+  @Before
+  public void setup(){
+    sampleSet = new HashSet<>();
+    sampleSet.add(4);
+    sampleSet.add(5);
+    sampleSet.add(12);
+  }
+
+  @Test
+  public void setConstructorTest(){
+    Assert.assertEquals(new LWWSet<>(sampleSet).value(), sampleSet);
+  }
+
+  @Test
+  public void stressWithSetTest(){
+    Set<Integer> set = new HashSet<>();
+    LWWSet<Integer> lww = new LWWSet<>();
+    for (int it = 0; it < 100; it++){
+      LWWSet<Integer> newLww;
+      if (it % 5 == 1){
+        //deleting existing
+        Integer forDelete = set.stream().skip((long) (set.size() * Math.random())).findFirst().get();
+        newLww = lww.remove(forDelete);
+        Assert.assertEquals(lww.value(), set); // check old version is immutable
+        set.remove(forDelete);
+      } else {
+        //adding
+        Integer forAdd = (int) (10000 * Math.random());
+        newLww = lww.add(forAdd);
+        Assert.assertEquals(lww.value(), set); // check old version is immutable
+        set.add(forAdd);
+      }
+      lww = newLww;
+      Assert.assertEquals(lww.value(), set);
+    }
+  }
+
+  @Test
+  public void equalsTest(){
+    LWWSet<Integer> lww = new LWWSet<>(sampleSet);
+    Assert.assertFalse(lww.equals(sampleSet));
+    LWWSet<Integer> newLww = lww.add(25);
+    sampleSet.add(25);
+    Assert.assertFalse(newLww.equals(lww));
+    Assert.assertEquals(new LWWSet<>(sampleSet), newLww);
+  }
+
+  @Test
+  public void valueTest() {
+    Map<Character, LWWSet.Timestamps> map = new HashMap<>();
+    map.put('a', new LWWSet.Timestamps(1, 0));
+    map.put('b', new LWWSet.Timestamps(1, 2));
+    map.put('c', new LWWSet.Timestamps(3, 3));
+    Set<Character> toTest = new HashSet<>();
+    toTest.add('a'); // for 'a' addTime > removeTime
+    toTest.add('c'); // for 'c' times are equal, we prefer add to remove
+    Assert.assertEquals(new LWWSet<>(map).value(), toTest);
+    Assert.assertEquals(new LWWSet<>(map), new LWWSet<>('a', 'c'));
+  }
+
+  @Test
+  public void removeMissingTest(){
+    LWWSet<Integer> lww = new LWWSet<>(sampleSet);
+    lww = lww.add(25);
+    lww = lww.remove(25);
+    Assert.assertEquals(lww.value(), sampleSet);
+    lww = lww.remove(25);
+    lww = lww.add(25);
+    sampleSet.add(25);
+    Assert.assertEquals(lww.value(), sampleSet);
+  }
+
+  @Test
+  public void stressMergeTest(){
+    // in one-process context, add, remove and merge operations of lww are equal to operations of Set
+    // we've already checked it. Now just check merge
+    Set<Integer> set1 = new HashSet<>(), set2 = new HashSet<>();
+    LWWSet<Integer> lww1 = new LWWSet<>(), lww2 = new LWWSet<>();
+
+    for (int it = 0; it < 100; it++){
+      Integer forAdd = (int) (10000 * Math.random());
+      if (it % 2 == 0){
+        set1.add(forAdd);
+        lww1 = lww1.add(forAdd);
+      } else {
+        set2.add(forAdd);
+        lww2 = lww2.add(forAdd);
+      }
+    }
+    Assert.assertEquals(lww1.value(), set1);
+    Assert.assertEquals(lww2.value(), set2);
+    Set<Integer> mergedSet = Stream.concat(set1.stream(), set2.stream()).collect(Collectors.toSet());
+    Assert.assertEquals(lww1.merge(lww2).value(), mergedSet);
+  }
+
+  @Test
+  public void fakeTimeMergeTest(){
+    // try to create LWWSet with time from future (simulate other process with its own clock) and validate result
+    // check remove from the future
+    Map<Integer, LWWSet.Timestamps> map = new HashMap<>();
+    map.put(25, new LWWSet.Timestamps(clock.nanoTime(), clock.nanoTime() + 100000));
+    LWWSet<Integer> lww = new LWWSet<>(map);
+    Assert.assertEquals(lww, new LWWSet<Integer>());
+    //create new LWWSet with element 25, and merge with other LWW which has remove in future
+    Assert.assertEquals(new LWWSet<>(25).merge(lww), new LWWSet<Integer>());
+
+    // add in future
+    map.put(25, new LWWSet.Timestamps(clock.nanoTime() + 100000, 0));
+    lww = new LWWSet<>(map);
+    lww = lww.remove(25);
+    Assert.assertEquals(lww, new LWWSet<>(25)); // 25 is still here
+  }
+
+  @Test
+  public void optimizeTest(){
+    Assert.assertEquals(new LWWSet<>(sampleSet).value(), sampleSet);
+    Assert.assertEquals(new LWWSet<>(sampleSet).optimize().value(), sampleSet);
+  }
+}

gossip-itest/src/test/java/org/apache/gossip/DataTest.java

@@ -17,222 +17,191 @@
  */
 package org.apache.gossip;
 
-import java.net.URI;
-import java.net.URISyntaxException;
-import java.net.UnknownHostException;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-import java.util.UUID;
-import java.util.concurrent.TimeUnit;
-
+import io.teknek.tunit.TUnit;
 import org.apache.gossip.crdt.GrowOnlyCounter;
 import org.apache.gossip.crdt.GrowOnlySet;
+import org.apache.gossip.crdt.LWWSet;
 import org.apache.gossip.crdt.OrSet;
 import org.apache.gossip.manager.GossipManager;
 import org.apache.gossip.manager.GossipManagerBuilder;
 import org.apache.gossip.model.PerNodeDataMessage;
 import org.apache.gossip.model.SharedDataMessage;
+import org.junit.Assert;
 import org.junit.Test;
 
-import io.teknek.tunit.TUnit;
- 
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.UnknownHostException;
+import java.util.*;
+import java.util.concurrent.TimeUnit;
+
 public class DataTest extends AbstractIntegrationBase {
-  
+
   private String orSetKey = "cror";
+  private String lwwSetKey = "crlww";
   private String gCounterKey = "crdtgc";
-  
+
   @Test
   public void dataTest() throws InterruptedException, UnknownHostException, URISyntaxException{
     GossipSettings settings = new GossipSettings();
-    settings.setPersistRingState(false); 
+    settings.setPersistRingState(false);
     settings.setPersistDataState(false);
     String cluster = UUID.randomUUID().toString();
     int seedNodes = 1;
     List<Member> startupMembers = new ArrayList<>();
-    for (int i = 1; i < seedNodes+1; ++i) {
+    for (int i = 1; i < seedNodes + 1; ++i){
       URI uri = new URI("udp://" + "127.0.0.1" + ":" + (50000 + i));
       startupMembers.add(new RemoteMember(cluster, uri, i + ""));
     }
     final List<GossipManager> clients = new ArrayList<>();
     final int clusterMembers = 2;
-    for (int i = 1; i < clusterMembers + 1; ++i) {
+    for (int i = 1; i < clusterMembers + 1; ++i){
       URI uri = new URI("udp://" + "127.0.0.1" + ":" + (50000 + i));
       GossipManager gossipService = GossipManagerBuilder.newBuilder().cluster(cluster).uri(uri)
-              .id(i + "").gossipMembers(startupMembers).gossipSettings(settings).build();
+          .id(i + "").gossipMembers(startupMembers).gossipSettings(settings).build();
       clients.add(gossipService);
       gossipService.init();
       register(gossipService);
     }
     TUnit.assertThat(() -> {
       int total = 0;
-      for (int i = 0; i < clusterMembers; ++i) {
+      for (int i = 0; i < clusterMembers; ++i){
         total += clients.get(i).getLiveMembers().size();
       }
       return total;
     }).afterWaitingAtMost(20, TimeUnit.SECONDS).isEqualTo(2);
-    clients.get(0).gossipPerNodeData(msg());
-    clients.get(0).gossipSharedData(sharedMsg());
+    clients.get(0).gossipPerNodeData(generatePerNodeMsg("a", "b"));
+    clients.get(0).gossipSharedData(generateSharedMsg("a", "c"));
 
-    TUnit.assertThat(()-> {
+    TUnit.assertThat(() -> {
       PerNodeDataMessage x = clients.get(1).findPerNodeGossipData(1 + "", "a");
       if (x == null)
         return "";
       else
         return x.getPayload();
     }).afterWaitingAtMost(20, TimeUnit.SECONDS).isEqualTo("b");
-   
-    TUnit.assertThat(() ->  {
+
+    TUnit.assertThat(() -> {
       SharedDataMessage x = clients.get(1).findSharedGossipData("a");
       if (x == null)
         return "";
       else
         return x.getPayload();
     }).afterWaitingAtMost(20, TimeUnit.SECONDS).isEqualTo("c");
-    
-    
+
+
     givenDifferentDatumsInSet(clients);
     assertThatListIsMerged(clients);
-    
-    givenOrs(clients);
-    assertThatOrSetIsMerged(clients);
-    dropIt(clients);
-    assertThatOrSetDelIsMerged(clients);
 
-    
+    testOrSet(clients);
+    testLWWSet(clients);
+
     // test g counter
     givenDifferentIncrement(clients);
     assertThatCountIsUpdated(clients, 3);
     givenIncreaseOther(clients);
     assertThatCountIsUpdated(clients, 7);
 
-    for (int i = 0; i < clusterMembers; ++i) {
+    for (int i = 0; i < clusterMembers; ++i){
       clients.get(i).shutdown();
     }
   }
-  
-  private void givenDifferentIncrement(final List<GossipManager> clients) {
-    {
-      SharedDataMessage d = new SharedDataMessage();
-      d.setKey(gCounterKey);
-      d.setPayload(new GrowOnlyCounter(new GrowOnlyCounter.Builder(clients.get(0)).increment(1L)));
-      d.setExpireAt(Long.MAX_VALUE);
-      d.setTimestamp(System.currentTimeMillis());
-      clients.get(0).merge(d);
-    }
-    {
-      SharedDataMessage d = new SharedDataMessage();
-      d.setKey(gCounterKey);
-      d.setPayload(new GrowOnlyCounter(new GrowOnlyCounter.Builder(clients.get(1)).increment(2L)));
-      d.setExpireAt(Long.MAX_VALUE);
-      d.setTimestamp(System.currentTimeMillis());
-      clients.get(1).merge(d);
-    }
-  }
 
-  private void givenIncreaseOther(final List<GossipManager> clients) {
-    GrowOnlyCounter gc = (GrowOnlyCounter) clients.get(1).findCrdt(gCounterKey);
-    GrowOnlyCounter gc2 = new GrowOnlyCounter(gc,
-            new GrowOnlyCounter.Builder(clients.get(1)).increment(4L));
+  private void testOrSet(final List<GossipManager> clients){
+    //populate
+    clients.get(0).merge(generateSharedMsg(orSetKey, new OrSet<>("1", "2")));
+    clients.get(1).merge(generateSharedMsg(orSetKey, new OrSet<>("3", "4")));
 
-    SharedDataMessage d = new SharedDataMessage();
-    d.setKey(gCounterKey);
-    d.setPayload(gc2);
-    d.setExpireAt(Long.MAX_VALUE);
-    d.setTimestamp(System.currentTimeMillis());
-    clients.get(1).merge(d);
-  }
+    //assert merge
+    assertMerged(clients.get(0), orSetKey, new OrSet<>("1", "2", "3", "4").value());
+    assertMerged(clients.get(1), orSetKey, new OrSet<>("1", "2", "3", "4").value());
 
-  private void givenOrs(List<GossipManager> clients) {
-    {
-      SharedDataMessage d = new SharedDataMessage();
-      d.setKey(orSetKey);
-      d.setPayload(new OrSet<String>("1", "2"));
-      d.setExpireAt(Long.MAX_VALUE);
-      d.setTimestamp(System.currentTimeMillis());
-      clients.get(0).merge(d);
-    }
-    {
-      SharedDataMessage d = new SharedDataMessage();
-      d.setKey(orSetKey);
-      d.setPayload(new OrSet<String>("3", "4"));
-      d.setExpireAt(Long.MAX_VALUE);
-      d.setTimestamp(System.currentTimeMillis());
-      clients.get(1).merge(d);
-    }
-  }
-  
-  private void dropIt(List<GossipManager> clients) {
+    //drop element
     @SuppressWarnings("unchecked")
     OrSet<String> o = (OrSet<String>) clients.get(0).findCrdt(orSetKey);
-    OrSet<String> o2 = new OrSet<String>(o, new OrSet.Builder<String>().remove("3"));
-    SharedDataMessage d = new SharedDataMessage();
-    d.setKey(orSetKey);
-    d.setPayload(o2);
-    d.setExpireAt(Long.MAX_VALUE);
-    d.setTimestamp(System.currentTimeMillis());
-    clients.get(0).merge(d);
+    OrSet<String> o2 = new OrSet<>(o, new OrSet.Builder<String>().remove("3"));
+    clients.get(0).merge(generateSharedMsg(orSetKey, o2));
+
+    //assert deletion
+    assertMerged(clients.get(0), orSetKey, new OrSet<>("1", "2", "4").value());
+    assertMerged(clients.get(1), orSetKey, new OrSet<>("1", "2", "4").value());
   }
-  
-  private void assertThatOrSetIsMerged(final List<GossipManager> clients){
-    TUnit.assertThat(() ->  {
-      return clients.get(0).findCrdt(orSetKey).value();
-    }).afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(new OrSet<String>("1", "2", "3", "4").value());
-    TUnit.assertThat(() ->  {
-      return clients.get(1).findCrdt(orSetKey).value();
-    }).afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(new OrSet<String>("1", "2", "3", "4").value());
+
+  private void testLWWSet(final List<GossipManager> clients){
+    //populate
+    clients.get(0).merge(generateSharedMsg(lwwSetKey, new LWWSet<>("1", "2")));
+    clients.get(1).merge(generateSharedMsg(lwwSetKey, new LWWSet<>("3", "4")));
+
+    //assert merge
+    assertMerged(clients.get(0), lwwSetKey, new LWWSet<>("1", "2", "3", "4").value());
+    assertMerged(clients.get(1), lwwSetKey, new LWWSet<>("1", "2", "3", "4").value());
+
+    //drop element
+    @SuppressWarnings("unchecked")
+    LWWSet<String> lww = (LWWSet<String>) clients.get(0).findCrdt(lwwSetKey);
+    clients.get(0).merge(generateSharedMsg(lwwSetKey, lww.remove("3")));
+
+    //assert deletion
+    assertMerged(clients.get(0), lwwSetKey, new OrSet<>("1", "2", "4").value());
+    assertMerged(clients.get(1), lwwSetKey, new OrSet<>("1", "2", "4").value());
   }
-  
-  private void assertThatOrSetDelIsMerged(final List<GossipManager> clients){
-    TUnit.assertThat(() ->  {
-      return clients.get(0).findCrdt(orSetKey);
-    }).afterWaitingAtMost(10, TimeUnit.SECONDS).equals(new OrSet<String>("1", "2", "4"));
+
+  private void givenDifferentIncrement(final List<GossipManager> clients){
+    Object payload = new GrowOnlyCounter(new GrowOnlyCounter.Builder(clients.get(0)).increment(1L));
+    clients.get(0).merge(generateSharedMsg(gCounterKey, payload));
+    payload = new GrowOnlyCounter(new GrowOnlyCounter.Builder(clients.get(1)).increment(2L));
+    clients.get(1).merge(generateSharedMsg(gCounterKey, payload));
+  }
+
+  private void givenIncreaseOther(final List<GossipManager> clients){
+    GrowOnlyCounter gc = (GrowOnlyCounter) clients.get(1).findCrdt(gCounterKey);
+    GrowOnlyCounter gc2 = new GrowOnlyCounter(gc,
+        new GrowOnlyCounter.Builder(clients.get(1)).increment(4L));
+
+    clients.get(1).merge(generateSharedMsg(gCounterKey, gc2));
+  }
+
+  private void assertMerged(final GossipManager client, String key, final Set<String> expected){
+    TUnit.assertThat(() -> client.findCrdt(key).value())
+        .afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(expected);
   }
 
   private void givenDifferentDatumsInSet(final List<GossipManager> clients){
     clients.get(0).merge(CrdtMessage("1"));
     clients.get(1).merge(CrdtMessage("2"));
   }
-  
 
-  private void assertThatCountIsUpdated(final List<GossipManager> clients, long finalCount) {
-    TUnit.assertThat(() -> {
-      return clients.get(0).findCrdt(gCounterKey);
-    }).afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(new GrowOnlyCounter(
-            new GrowOnlyCounter.Builder(clients.get(0)).increment(finalCount)));
+
+  private void assertThatCountIsUpdated(final List<GossipManager> clients, long finalCount){
+    TUnit.assertThat(() -> clients.get(0).findCrdt(gCounterKey))
+        .afterWaitingAtMost(10, TimeUnit.SECONDS)
+        .isEqualTo(new GrowOnlyCounter(new GrowOnlyCounter.Builder(clients.get(0)).increment(finalCount)));
   }
 
   private void assertThatListIsMerged(final List<GossipManager> clients){
-    TUnit.assertThat(() ->  {
-      return clients.get(0).findCrdt("cr");
-    }).afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(new GrowOnlySet<String>(Arrays.asList("1","2")));
+    TUnit.assertThat(() -> clients.get(0).findCrdt("cr"))
+        .afterWaitingAtMost(10, TimeUnit.SECONDS).isEqualTo(new GrowOnlySet<>(Arrays.asList("1", "2")));
   }
-  
+
   private SharedDataMessage CrdtMessage(String item){
+    return generateSharedMsg("cr", new GrowOnlySet<>(Arrays.asList(item)));
+  }
+
+  private PerNodeDataMessage generatePerNodeMsg(String key, Object payload){
+    PerNodeDataMessage g = new PerNodeDataMessage();
+    g.setExpireAt(Long.MAX_VALUE);
+    g.setKey(key);
+    g.setPayload(payload);
+    g.setTimestamp(System.currentTimeMillis());
+    return g;
+  }
+
+  private SharedDataMessage generateSharedMsg(String key, Object payload){
     SharedDataMessage d = new SharedDataMessage();
-    d.setKey("cr");
-    d.setPayload(new GrowOnlySet<String>( Arrays.asList(item)));
+    d.setKey(key);
+    d.setPayload(payload);
     d.setExpireAt(Long.MAX_VALUE);
     d.setTimestamp(System.currentTimeMillis());
     return d;
   }
-  
-  private PerNodeDataMessage msg(){
-    PerNodeDataMessage g = new PerNodeDataMessage();
-    g.setExpireAt(Long.MAX_VALUE);
-    g.setKey("a");
-    g.setPayload("b");
-    g.setTimestamp(System.currentTimeMillis());
-    return g;
-  }
-  
-  private SharedDataMessage sharedMsg(){
-    SharedDataMessage g = new SharedDataMessage();
-    g.setExpireAt(Long.MAX_VALUE);
-    g.setKey("a");
-    g.setPayload("c");
-    g.setTimestamp(System.currentTimeMillis());
-    return g;
-  }
-  
-}
+}

gossip-protocol-jackson/src/test/java/org/apache/gossip/protocol/json/JacksonTest.java

@@ -22,6 +22,7 @@ import com.codahale.metrics.MetricRegistry;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.gossip.GossipSettings;
 import org.apache.gossip.Member;
+import org.apache.gossip.crdt.LWWSet;
 import org.apache.gossip.crdt.OrSet;
 import org.apache.gossip.manager.GossipManager;
 import org.apache.gossip.manager.GossipManagerBuilder;
@@ -80,6 +81,22 @@ public class JacksonTest {
     OrSet<Integer> back = objectMapper.readValue(s, OrSet.class);
     Assert.assertEquals(back, i);
   }
+
+  @Test
+  public void jacksonCrdtLWWSetTest() {
+    ObjectMapper objectMapper = JacksonProtocolManager.buildObjectMapper(simpleSettings(new GossipSettings()));
+
+    LWWSet<String> lww = new LWWSet<>("a", "b", "c");
+
+    try {
+      String lwwS = objectMapper.writeValueAsString(lww);
+      @SuppressWarnings("unchecked")
+      LWWSet<String> parsedLww = objectMapper.readValue(lwwS, LWWSet.class);
+      Assert.assertEquals(lww, parsedLww);
+    } catch (Exception e) {
+      Assert.fail("LWWSet se/de error");
+    }
+  }
   
   @Test
   public void testMessageEqualityAssumptions() {