Changed live and dead methods to return immutable lists. changed the underlying datastructure to be a map as opposed to two list

src/main/java/com/google/code/gossip/GossipMember.java

@@ -10,25 +10,15 @@ import org.json.JSONObject;
  * 
  * @author joshclemm, harmenw
  */
-public abstract class GossipMember {
+public abstract class GossipMember implements Comparable<GossipMember>{
-	/** The JSON key for the host property. */
+	
 	public static final String JSON_HOST = "host";
-	/** The JSON key for the port property. */
 	public static final String JSON_PORT = "port";
-	/** The JSON key for the heartbeat property. */
 	public static final String JSON_HEARTBEAT = "heartbeat";
-	
 	public static final String JSON_ID = "id";
-
-	/** The hostname or IP address of this gossip member. */
 	protected String _host;
-	
-	/** The port number of this gossip member. */
 	protected int _port;
-
-	/** The current heartbeat of this gossip member. */
 	protected int _heartbeat;
-	
 	protected String _id;
 	
 	/**
@@ -146,4 +136,8 @@ public abstract class GossipMember {
 			throw new RuntimeException(e);
 		}
 	}
+	
+	public int compareTo(GossipMember other){
+	  return this.getAddress().compareTo(other.getAddress());
+	}
 }

src/main/java/com/google/code/gossip/GossipTimeoutTimer.java

@@ -14,10 +14,7 @@ import javax.management.timer.Timer;
  */
 public class GossipTimeoutTimer extends Timer {
 
-  /** The amount of time this timer waits before generating a wake-up event. */
   private long _sleepTime;
-
-  /** The gossip member this timer is for. */
   private LocalGossipMember _source;
 
   /**

src/main/java/com/google/code/gossip/manager/ActiveGossipThread.java

@@ -1,6 +1,7 @@
 package com.google.code.gossip.manager;
 
 import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -45,7 +46,7 @@ abstract public class ActiveGossipThread implements Runnable {
    * Performs the sending of the membership list, after we have incremented our own heartbeat.
    */
   abstract protected void sendMembershipList(LocalGossipMember me,
-          ArrayList<LocalGossipMember> memberList);
+          List<LocalGossipMember> memberList);
 
   /**
    * Abstract method which should be implemented by a subclass. This method should return a member
@@ -55,5 +56,5 @@ abstract public class ActiveGossipThread implements Runnable {
    *          The list of members which are stored in the local list of members.
    * @return The chosen LocalGossipMember to gossip with.
    */
-  abstract protected LocalGossipMember selectPartner(ArrayList<LocalGossipMember> memberList);
+  abstract protected LocalGossipMember selectPartner(List<LocalGossipMember> memberList);
 }

src/main/java/com/google/code/gossip/manager/GossipManager.java

@@ -2,6 +2,10 @@ package com.google.code.gossip.manager;
 
 import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
@@ -20,34 +24,16 @@ import com.google.code.gossip.LocalGossipMember;
 public abstract class GossipManager extends Thread implements NotificationListener {
   
   public static final Logger LOGGER = Logger.getLogger(GossipManager.class);
-  
-  /** The maximal number of bytes the packet with the GOSSIP may be. (Default is 100 kb) */
   public static final int MAX_PACKET_SIZE = 102400;
 
-  /** The list of members which are in the gossip group (not including myself). */
+  private ConcurrentSkipListMap<LocalGossipMember,String> members;
-  private ArrayList<LocalGossipMember> _memberList;
-
-  /** The list of members which are known to be dead. */
-  private ArrayList<LocalGossipMember> _deadList;
-
-  /** The member I am representing. */
   private LocalGossipMember _me;
-
-  /** The settings for gossiping. */
   private GossipSettings _settings;
-
-  /** A boolean whether the gossip service should keep running. */
   private AtomicBoolean _gossipServiceRunning;
-
-  /** A ExecutorService used for executing the active and passive gossip threads. */
   private ExecutorService _gossipThreadExecutor;
-
   private Class<? extends PassiveGossipThread> _passiveGossipThreadClass;
-
   private PassiveGossipThread passiveGossipThread;
-
   private Class<? extends ActiveGossipThread> _activeGossipThreadClass;
-
   private ActiveGossipThread activeGossipThread;
 
   public GossipManager(Class<? extends PassiveGossipThread> passiveGossipThreadClass,
@@ -57,14 +43,13 @@ public abstract class GossipManager extends Thread implements NotificationListen
     _activeGossipThreadClass = activeGossipThreadClass;
     _settings = settings;
     _me = new LocalGossipMember(address, port, id, 0, this, settings.getCleanupInterval());
-    _memberList = new ArrayList<LocalGossipMember>();
+    members = new ConcurrentSkipListMap<>();
-    _deadList = new ArrayList<LocalGossipMember>();
     for (GossipMember startupMember : gossipMembers) {
       if (!startupMember.equals(_me)) {
         LocalGossipMember member = new LocalGossipMember(startupMember.getHost(),
                 startupMember.getPort(), startupMember.getId(), 0, this,
                 settings.getCleanupInterval());
-        _memberList.add(member);
+        members.put(member, "UP");
         GossipService.LOGGER.debug(member);
       }
     }
@@ -85,33 +70,39 @@ public abstract class GossipManager extends Thread implements NotificationListen
   public void handleNotification(Notification notification, Object handback) {
     LocalGossipMember deadMember = (LocalGossipMember) notification.getUserData();
     GossipService.LOGGER.info("Dead member detected: " + deadMember);
-    synchronized (this._memberList) {
+    members.put(deadMember, "DOWN");
-      this._memberList.remove(deadMember);
-    }
-    synchronized (this._deadList) {
-      this._deadList.add(deadMember);
-    }
   }
 
   public GossipSettings getSettings() {
     return _settings;
   }
 
-  /**
+  public List<LocalGossipMember> getMemberList() {
-   * Get a clone of the memberlist.
+    List<LocalGossipMember> up = new ArrayList<>();
-   * 
+    for (Entry<LocalGossipMember, String> entry : members.entrySet()){
-   * @return
+      if ("UP".equals(entry.getValue())){
-   */
+        up.add(entry.getKey());
-  public ArrayList<LocalGossipMember> getMemberList() {
+      }
-    return _memberList;
+    }
+    return Collections.unmodifiableList(up);
   }
 
   public LocalGossipMember getMyself() {
     return _me;
   }
+  
+  public void createOrRevivieMember(LocalGossipMember m){
+    members.put(m, "UP");
+  }
 
-  public ArrayList<LocalGossipMember> getDeadList() {
+  public List<LocalGossipMember> getDeadList() {
-    return _deadList;
+    List<LocalGossipMember> up = new ArrayList<>();
+    for (Entry<LocalGossipMember, String> entry : members.entrySet()){
+      if ("DOWN".equals(entry.getValue())){
+        up.add(entry.getKey());
+      }
+    }
+    return Collections.unmodifiableList(up);
   }
 
   /**
@@ -121,7 +112,7 @@ public abstract class GossipManager extends Thread implements NotificationListen
    * @throws InterruptedException
    */
   public void run() {
-    for (LocalGossipMember member : _memberList) {
+    for (LocalGossipMember member : members.keySet()) {
       if (member != _me) {
         member.startTimeoutTimer();
       }

src/main/java/com/google/code/gossip/manager/PassiveGossipThread.java

@@ -7,6 +7,7 @@ import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.net.SocketException;
 import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.json.JSONArray;
@@ -144,5 +145,5 @@ abstract public class PassiveGossipThread implements Runnable {
    *          The list of members known at the remote side.
    */
   abstract protected void mergeLists(GossipManager gossipManager, RemoteGossipMember senderMember,
-          ArrayList<GossipMember> remoteList);
+          List<GossipMember> remoteList);
 }

src/main/java/com/google/code/gossip/manager/impl/OnlyProcessReceivedPassiveGossipThread.java

@@ -1,6 +1,6 @@
 package com.google.code.gossip.manager.impl;
 
-import java.util.ArrayList;
+import java.util.List;
 
 import com.google.code.gossip.GossipMember;
 import com.google.code.gossip.GossipService;
@@ -23,35 +23,21 @@ public class OnlyProcessReceivedPassiveGossipThread extends PassiveGossipThread
    * @param remoteList
    */
   protected void mergeLists(GossipManager gossipManager, RemoteGossipMember senderMember,
-          ArrayList<GossipMember> remoteList) {
+          List<GossipMember> remoteList) {
-
-    synchronized (gossipManager.getDeadList()) {
-
-      synchronized (gossipManager.getMemberList()) {
 
         for (GossipMember remoteMember : remoteList) {
           // Skip myself. We don't want ourselves in the local member list.
-          if (!remoteMember.equals(gossipManager.getMyself())) {
+          if (remoteMember.equals(gossipManager.getMyself())) {
+            continue;
+          }
             if (gossipManager.getMemberList().contains(remoteMember)) {
-              GossipService.LOGGER.debug("The local list already contains the remote member ("
-                      + remoteMember + ").");
-              // The local memberlist contains the remote member.
               LocalGossipMember localMember = gossipManager.getMemberList().get(
                       gossipManager.getMemberList().indexOf(remoteMember));
-
-              // Let's synchronize it's heartbeat.
               if (remoteMember.getHeartbeat() > localMember.getHeartbeat()) {
-                // update local list with latest heartbeat
                 localMember.setHeartbeat(remoteMember.getHeartbeat());
-                // and reset the timeout of that member
                 localMember.resetTimeoutTimer();
               }
-              // TODO: Otherwise, should we inform the other when the heartbeat is already higher?
             } else {
-              // The local list does not contain the remote member.
-              GossipService.LOGGER.debug("The local list does not contain the remote member ("
-                      + remoteMember + ").");
-
               // The remote member is either brand new, or a previously declared dead member.
               // If its dead, check the heartbeat because it may have come back from the dead.
               if (gossipManager.getDeadList().contains(remoteMember)) {
@@ -80,13 +66,14 @@ public class OnlyProcessReceivedPassiveGossipThread extends PassiveGossipThread
                           .debug("The remote member is back from the dead. We will remove it from the dead list and add it as a new member.");
                   // The remote member is back from the dead.
                   // Remove it from the dead list.
-                  gossipManager.getDeadList().remove(localDeadMember);
+                  //gossipManager.getDeadList().remove(localDeadMember);
                   // Add it as a new member and add it to the member list.
                   LocalGossipMember newLocalMember = new LocalGossipMember(remoteMember.getHost(),
                           remoteMember.getPort(), remoteMember.getId(),
                           remoteMember.getHeartbeat(), gossipManager, gossipManager.getSettings()
                                   .getCleanupInterval());
-                  gossipManager.getMemberList().add(newLocalMember);
+                  //gossipManager.getMemberList().add(newLocalMember);
+                  gossipManager.createOrRevivieMember(newLocalMember);
                   newLocalMember.startTimeoutTimer();
                   GossipService.LOGGER.info("Removed remote member " + remoteMember.getAddress()
                           + " from dead list and added to local member list.");
@@ -96,7 +83,7 @@ public class OnlyProcessReceivedPassiveGossipThread extends PassiveGossipThread
                 LocalGossipMember newLocalMember = new LocalGossipMember(remoteMember.getHost(),
                         remoteMember.getPort(), remoteMember.getId(), remoteMember.getHeartbeat(),
                         gossipManager, gossipManager.getSettings().getCleanupInterval());
-                gossipManager.getMemberList().add(newLocalMember);
+                gossipManager.createOrRevivieMember(newLocalMember);
                 newLocalMember.startTimeoutTimer();
                 GossipService.LOGGER.info("Added new remote member " + remoteMember.getAddress()
                         + " to local member list.");
@@ -104,8 +91,7 @@ public class OnlyProcessReceivedPassiveGossipThread extends PassiveGossipThread
             }
           }
         }
-      }
+
-    }
+  
-  }
 
 }

src/main/java/com/google/code/gossip/manager/impl/SendMembersActiveGossipThread.java

@@ -5,7 +5,7 @@ import java.net.DatagramPacket;
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.nio.ByteBuffer;
-import java.util.ArrayList;
+import java.util.List;
 
 import org.json.JSONArray;
 
@@ -23,7 +23,7 @@ abstract public class SendMembersActiveGossipThread extends ActiveGossipThread {
   /**
    * Performs the sending of the membership list, after we have incremented our own heartbeat.
    */
-  protected void sendMembershipList(LocalGossipMember me, ArrayList<LocalGossipMember> memberList) {
+  protected void sendMembershipList(LocalGossipMember me, List<LocalGossipMember> memberList) {
     GossipService.LOGGER.debug("Send sendMembershipList() is called.");
     me.setHeartbeat(me.getHeartbeat() + 1);
     synchronized (memberList) {

src/main/java/com/google/code/gossip/manager/random/RandomActiveGossipThread.java

@@ -1,6 +1,7 @@
 package com.google.code.gossip.manager.random;
 
 import java.util.ArrayList;
+import java.util.List;
 import java.util.Random;
 
 import com.google.code.gossip.GossipService;
@@ -24,7 +25,7 @@ public class RandomActiveGossipThread extends SendMembersActiveGossipThread {
    * 
    * @return Member random member if list is greater than 1, null otherwise
    */
-  protected LocalGossipMember selectPartner(ArrayList<LocalGossipMember> memberList) {
+  protected LocalGossipMember selectPartner(List<LocalGossipMember> memberList) {
     LocalGossipMember member = null;
     if (memberList.size() > 0) {
       int randomNeighborIndex = _random.nextInt(memberList.size());