Herd Effect in zookeeper solution

.idea/workspace.xml

@@ -42,6 +42,34 @@
       <recent name="D:\HIAST\FIY\FS\Distributed Systems\Lab\5\Session\ZookeeperProject" />
     </key>
   </component>
+  <component name="RunManager" selected="Application.C3">
+    <configuration name="C1" type="Application" factoryName="Application">
+      <option name="MAIN_CLASS_NAME" value="LeaderElection" />
+      <module name="ZookeeperProject" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <configuration name="C2" type="Application" factoryName="Application">
+      <option name="MAIN_CLASS_NAME" value="LeaderElection" />
+      <module name="ZookeeperProject" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <configuration name="C3" type="Application" factoryName="Application">
+      <option name="MAIN_CLASS_NAME" value="LeaderElection" />
+      <module name="ZookeeperProject" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <list>
+      <item itemvalue="Application.C1" />
+      <item itemvalue="Application.C2" />
+      <item itemvalue="Application.C3" />
+    </list>
+  </component>
   <component name="SpellCheckerSettings" RuntimeDictionaries="0" Folders="0" CustomDictionaries="0" DefaultDictionary="application-level" UseSingleDictionary="true" transferred="true" />
   <component name="TaskManager">
     <task active="true" id="Default" summary="Default task">

src/LeaderElection.java

@@ -2,6 +2,7 @@ import org.apache.zookeeper.*;
 import org.apache.zookeeper.data.Stat;
 
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -27,38 +28,42 @@ public class LeaderElection implements Watcher
         leaderElection.connectToZookeeper();
         leaderElection.volunteerForLeader();
         leaderElection.electLeader();
-        System.out.println(leaderElection.leader);
         leaderElection.run();
         leaderElection.close();
     }
 
     public void electLeader() throws InterruptedException, KeeperException
     {
-        List<String> children = zooKeeper.getChildren(ELECTION_NAMESPACE , this);
-        Collections.sort(children);
-        this.leader = children.get(0);
-        if (currentZnodeName.equals(leader))
-        {
-            prevZnode = currentZnodeName;
-        }
-        else
+        synchronized (zooKeeper)
         {
-            prevZnode = children.get(children.indexOf(currentZnodeName)-1);
+            List<String> children = zooKeeper.getChildren(ELECTION_NAMESPACE, this);
+            Collections.sort(children);
+            this.leader = children.get(0);
+            if (currentZnodeName.equals(leader))
+            {
+                prevZnode = currentZnodeName;
+            }
+            else
+            {
+                prevZnode = children.get(children.indexOf(currentZnodeName) - 1);
+                prevZnodeFullName = ELECTION_NAMESPACE + "/" + prevZnode;
+                Stat prevExist = zooKeeper.exists(prevZnodeFullName , this);
+            }
+
+            System.out.println("prevZnode from ElectLeader : " + prevZnode);
+            setLeaderInData();
         }
-        prevZnodeFullName = ELECTION_NAMESPACE+"/"+prevZnode;
-        setLeaderInData();
     }
 
     private void setLeaderInData() throws InterruptedException, KeeperException
     {
-        Stat temp = zooKeeper.exists(currentZondeFullName , false);
+        synchronized (zooKeeper){
         zooKeeper.setData(
                 currentZondeFullName,
                 leader.getBytes(),
-                temp.getVersion()
-        );
+                -1);
         System.out.println("The Leader is Set in Node's Data");
-        System.out.println("The Leader is : " + leader);
+        System.out.println("The Leader is : " + leader);}
     }
 
     private void volunteerForLeader() throws InterruptedException, KeeperException
@@ -67,6 +72,7 @@ public class LeaderElection implements Watcher
         String path = zooKeeper.create(znodePref , new byte[] {} , ZooDefs.Ids.OPEN_ACL_UNSAFE , CreateMode.EPHEMERAL_SEQUENTIAL);
         currentZondeFullName = path;
         this.currentZnodeName = path.replace(ELECTION_NAMESPACE + "/" , "");
+        System.out.println("I am Node " + currentZnodeName);
     }
 
     private void close()
@@ -93,22 +99,12 @@ public class LeaderElection implements Watcher
         }
     }
 
-    public boolean testTargetZnode() throws InterruptedException, KeeperException
-    {
-        Stat stat = zooKeeper.exists(TARET_ZNODE , this);
-        if (stat == null)
-        {
-            System.out.println(TARET_ZNODE + " not Exist");
-            return false;
-        }
-        System.out.println(stat.toString());
-        return true;
-    }
     public void process(WatchedEvent watchedEvent)
     {
         switch (watchedEvent.getType())
         {
-            case None: {
+            case None:
+            {
                 if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
                     System.out.println("Successfully connected to ZooKeeper");
                 } else if (watchedEvent.getState() == Event.KeeperState.Closed) {
@@ -123,6 +119,7 @@ public class LeaderElection implements Watcher
                         zooKeeper.notifyAll();
                     }
                 }
+                break;
             }
 
 
@@ -130,44 +127,48 @@ public class LeaderElection implements Watcher
             {
                 try
                 {
-                    Stat prevExist = zooKeeper.exists(prevZnodeFullName , false);
-                    if (prevExist == null && leader==prevZnode)
+                    System.out.println("Detecting Node Deleted ");
+                    System.out.println("prev full name is :  " + prevZnodeFullName);
+                    ///Stat prevExist = zooKeeper.exists(prevZnodeFullName, this);
+                    if (leader.equals(prevZnode))
                     {
                         this.leader = currentZnodeName;
+                        prevZnode = currentZnodeName;
+                        prevZnodeFullName = currentZondeFullName;
                         setLeaderInData();
                     }
                 }
-                catch (KeeperException e)
+                catch (InterruptedException e)
                 {
                     throw new RuntimeException(e);
                 }
-                catch (InterruptedException e)
-                {
+                catch (KeeperException e) {
                     throw new RuntimeException(e);
                 }
-
+                break;
             }
 
             case NodeDataChanged:
             {
                 try
                 {
-                    //System.out.println("ERROR IN Data CHANGED IF HAPPENED");
-                    Stat temp = new Stat();
-                     byte[] newLeader = zooKeeper.getData(prevZnodeFullName , false , temp);
-                    this.leader = newLeader.toString();
+                    System.out.println("Detecting Node Data Changed");
+                    byte[] newLeader = zooKeeper.getData(prevZnodeFullName, this, new Stat());
+                    this.leader = new String(newLeader, StandardCharsets.UTF_8);
                     setLeaderInData();
                 }
-                catch (KeeperException e)
+                catch (InterruptedException e)
                 {
                     throw new RuntimeException(e);
                 }
-                catch (InterruptedException e)
+                catch (KeeperException e)
                 {
                     throw new RuntimeException(e);
                 }
+                break;
             }
-            break;
+
+            default:break;
         }
     }
 }
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