damn that was fun finished this project

.gitignore

+target/

launch.sh

+/opt/zookeeper/bin/zkServer.sh start /opt/zookeeper/conf/zoo1.cfg
+/opt/zookeeper/bin/zkServer.sh start /opt/zookeeper/conf/zoo2.cfg
+/opt/zookeeper/bin/zkServer.sh start /opt/zookeeper/conf/zoo3.cfg

pom.xml

+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.ds.LeaderElection</groupId>
+  <artifactId>LeaderElection</artifactId>
+  <packaging>jar</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <name>LeaderElection</name>
+  <url>http://maven.apache.org</url>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>3.8.1</version>
+      <scope>test</scope>
+    </dependency>
+<!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
+<dependency>
+    <groupId>org.apache.zookeeper</groupId>
+    <artifactId>zookeeper</artifactId>
+    <version>3.8.5</version>
+</dependency>
+  </dependencies>
+<build>
+    <plugins>
+        <plugin>
+            <groupId>org.apache.maven.plugins</groupId>
+            <artifactId>maven-compiler-plugin</artifactId>
+            <version>3.10.1</version>
+            <configuration>
+                <source>17</source>
+                <target>17</target>
+            </configuration>
+        </plugin>
+        <plugin>
+            <groupId>org.codehaus.mojo</groupId>
+            <artifactId>exec-maven-plugin</artifactId>
+            <version>3.1.0</version>
+            <configuration>
+                <mainClass>com.ds.LeaderElection.App</mainClass>
+            </configuration>
+        </plugin>
+    </plugins>
+</build>
+</project>

src/main/java/com/ds/LeaderElection/App.java

+package com.ds.LeaderElection;
+
+public class App {
+
+    public static void main(String[] args) throws Exception {
+
+        
+        ZKConnection zkConnection = new ZKConnection();
+        var zk = zkConnection.connect("localhost:2183");  //zoo3.cfg 
+        // Create a leader election participant
+        LeaderElection election = new LeaderElection(zk);
+
+        // Volunteer for leadership (creates ephemeral sequential node)
+        election.volunteerForLeadership();
+
+        // Begin election process
+        election.electLeader();
+
+        
+
+
+        // might figure out something better 
+        zkConnection.close();
+    }
+}

src/main/java/com/ds/LeaderElection/LeaderElection.java

+package com.ds.LeaderElection;
+
+import org.apache.zookeeper.*;
+import org.apache.zookeeper.data.Stat;
+
+import java.util.List;
+
+public class LeaderElection implements Watcher {
+    private ZooKeeper zooKeeper;
+    private String currentNode;
+    private static final String ELECTION_NODE = "/election";
+
+    public LeaderElection(ZooKeeper zooKeeper) {
+        this.zooKeeper = zooKeeper;
+    }
+
+    public void volunteerForLeadership() throws Exception {
+        // first time check
+        Stat stat = zooKeeper.exists(ELECTION_NODE, false);
+        if (stat == null) {
+            zooKeeper.create(ELECTION_NODE, new byte[] {}, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); // this
+                                                                                                                // is
+                                                                                                                // presistent
+        }
+
+        // Create ephemeral sequential node
+        currentNode = zooKeeper.create(ELECTION_NODE + "/node_", new byte[] {},
+                ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
+        System.out.println("Node created: " + currentNode);
+    }
+
+    public void electLeader() throws Exception {
+        while (true) {
+            List<String> children = zooKeeper.getChildren(ELECTION_NODE, false);
+            children.sort(String::compareTo);
+
+            String smallestNode = children.get(0);
+            String currentNodeName = currentNode.substring(currentNode.lastIndexOf("/") + 1);
+
+            if (currentNodeName.equals(smallestNode)) {
+                System.out.println(currentNode + " is the leader THIS IS MEEEE :) ");
+                // Keep leader alive (e.g. 60 seconds)
+                synchronized (this) {
+                    wait();
+                }
+            } else {
+                System.out.println(currentNode + "I am not the leader so sad :(");
+                // Find the node immediately before current node
+                int index = children.indexOf(currentNodeName) - 1;
+                String watchNode = children.get(index);
+
+                final Object lock = new Object();
+
+                // Watch the previous node
+                zooKeeper.exists(ELECTION_NODE + "/" + watchNode, event -> {
+                    if (event.getType() == Event.EventType.NodeDeleted) {
+                        synchronized (lock) {
+                            lock.notifyAll();
+                        }
+                    }
+                });
+
+                // Wait until the previous node is deleted
+                synchronized (lock) {
+                    lock.wait();
+                }
+            }
+        }
+    }
+
+    @Override
+    public void process(WatchedEvent event) {
+
+    }
+}

src/main/java/com/ds/LeaderElection/ZKConnection.java

+package com.ds.LeaderElection;
+
+import org.apache.zookeeper.ZooKeeper;
+import java.io.IOException;
+
+public class ZKConnection {
+    private ZooKeeper zoo;
+    //host contains 2181 
+    //this code is a simple wrapper it just connect to our backend
+    public ZooKeeper connect(String host) throws IOException {
+        zoo = new ZooKeeper(host, 3000, event -> {
+            
+        });
+        return zoo;
+    }
+    // this function just close the tcp connections
+    public void close() throws InterruptedException {
+        if (zoo != null) {
+            zoo.close();
+        }
+    }
+}

src/main/resources/log4j.properties

+log4j.rootLogger=ERROR, stdout
+
+log4j.appender.stdout=org.apache.log4j.ConsoleAppender
+log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
+log4j.appender.stdout.layout.ConversionPattern=%m%n
+
+# Silence the Zookeeper client
+log4j.logger.org.apache.zookeeper=ERROR
+log4j.logger.org.apache.zookeeper.ClientCnxn=ERROR
+log4j.logger.org.apache.zookeeper.ZooKeeper=ERROR

src/test/java/com/ds/LeaderElection/AppTest.java

+package com.ds.LeaderElection;
+
+import junit.framework.Test;
+import junit.framework.TestCase;
+import junit.framework.TestSuite;
+
+/**
+ * Unit test for simple App.
+ */
+public class AppTest 
+    extends TestCase
+{
+    /**
+     * Create the test case
+     *
+     * @param testName name of the test case
+     */
+    public AppTest( String testName )
+    {
+        super( testName );
+    }
+
+    /**
+     * @return the suite of tests being tested
+     */
+    public static Test suite()
+    {
+        return new TestSuite( AppTest.class );
+    }
+
+    /**
+     * Rigourous Test :-)
+     */
+    public void testApp()
+    {
+        assertTrue( true );
+    }
+}