Curator框架中的Leader选举

一、引入jar包

<!--引入zk依赖-->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.6.1</version>
    <!--排除这个slf4j-log4j12-->
    <exclusions>
        <exclusion>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<!--引入curator依赖-->
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-client</artifactId>
    <version>4.2.0</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>4.2.0</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>4.2.0</version>
</dependency>

二、使用示例

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.leader.LeaderLatch;
import org.apache.curator.framework.recipes.leader.LeaderLatchListener;
import org.apache.curator.retry.ExponentialBackoffRetry;

import java.io.IOException;

public class LeaderLatchTest {
    private static final String PATH = "/leader";
    private static final String APP_ID = "001";

    public static void main(String[] args) throws IOException {
        CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", new ExponentialBackoffRetry(1000, 3));
        client.start();
        LeaderLatch leaderLatch = new LeaderLatch(client, PATH, APP_ID);
        leaderLatch.addListener(new LeaderLatchListener() {
            /**
             * isLeader 中的方法会在实例被选为主节点后被执行, 而notLeader中的不会被执行
             * 如果主节点被失效, 会进行重新选主
             */
            @Override
            public void isLeader() {
                System.out.println("======= [LeaderLatch]我是主节点, app_id={" + leaderLatch.getId() + "} =========");
            }

            /**
             * 当丢失leader的时候被执行
             */
            @Override
            public void notLeader() {
                System.out.println("======= [LeaderLatch]我不是主节点, app_id={" + leaderLatch.getId() + "} =========");
            }
        });


        try {
            leaderLatch.start();
            while (true) {
                Thread.sleep(10000);
                System.out.println("======= " + leaderLatch.getLeader() + " ==========");
            }
        } catch (Exception e) {
            e.printStackTrace();
            leaderLatch.close();
            client.close();
        }
    }

}

温馨提示：在idea中更改APP_ID，开启多个main并行执行，即可模拟集群选举效果。

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