Zookeeper基于tomcat服务器(Valve)Master选举实例

环境准备

eclipse环境，使用tomcat8.5和tomcat9作为服务器，两个服务器中选一个作为master，zookeeper-3.4.10
在eclipse上部署两个服务器详见https://blog.csdn.net/SUNBOYmxbsH/article/details/78824963

创建maven项目，导入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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>ai.zixing</groupId><artifactId>zkDemo</artifactId><version>0.0.1-SNAPSHOT</version><name>zkDemo</name><description>zk-test</description><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><spring.version>4.3.8.RELEASE</spring.version></properties><dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-core</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-jdbc</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-test</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.apache.zookeeper</groupId><artifactId>zookeeper</artifactId><version>3.4.10</version></dependency><dependency><groupId>com.101tec</groupId><artifactId>zkclient</artifactId><version>0.10</version></dependency><dependency><groupId>org.apache.curator</groupId><artifactId>curator-framework</artifactId><version>4.0.0</version></dependency><dependency><groupId>org.apache.curator</groupId><artifactId>curator-recipes</artifactId><version>4.0.0</version></dependency><dependency><groupId>com.zaxxer</groupId><artifactId>HikariCP</artifactId><version>2.7.1</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.41</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>2.9.1</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.9.1</version></dependency><dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId><version>1.7.25</version></dependency><dependency><groupId>org.slf4j</groupId><artifactId>jcl-over-slf4j</artifactId><version>1.7.25</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency><dependency><groupId>commons-codec</groupId><artifactId>commons-codec</artifactId><version>1.11</version></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.5.1</version><configuration><source>1.8</source><target>1.8</target><encoding>UTF-8</encoding></configuration></plugin><plugin><groupId>org.xolstice.maven.plugins</groupId><artifactId>protobuf-maven-plugin</artifactId><version>0.5.0</version><configuration><protocArtifact>com.google.protobuf:protoc:3.0.0:exe:${os.detected.classifier}</protocArtifact><pluginId>grpc-java</pluginId><pluginArtifact>io.grpc:protoc-gen-grpc-java:1.0.0:exe:${os.detected.classifier}</pluginArtifact></configuration><executions><execution><goals><goal>compile</goal><goal>compile-custom</goal></goals></execution></executions></plugin></plugins></build>
</project>

编写测试类

package ai.zixing;import java.io.IOException;import javax.servlet.ServletException;import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.valves.ValveBase;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.TreeCache;
import org.apache.curator.framework.recipes.cache.TreeCacheEvent;
import org.apache.curator.framework.recipes.cache.TreeCacheListener;
import org.apache.curator.framework.recipes.cache.TreeCacheEvent.Type;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.CreateMode;public class ZkTomcatValve extends ValveBase {// Curator 访问ZK的实例private static CuratorFramework client;// 实例化Curator的Watcher（小宫女:监视皇帝）private static TreeCache treeCache;// zookeeper临时节点用来进行master选举(传国玉玺，谁拿到谁就是皇帝)private final static String path = "/Tomcat/ActiveLock";// 服务器名称(两个皇子：tomcat8.5和tomcat9)private String serverName;@Overridepublic void invoke(Request request, Response response) throws IOException, ServletException {// 初始化Curator客户端连接client = CuratorFrameworkFactory.builder().connectString("xx.xx.xx.xx:2181").connectionTimeoutMs(3000).retryPolicy(new ExponentialBackoffRetry(1000, 3)).build();client.start();// 创建临时节点的过程，谁创建成功谁就是master，拿到玉玺继承皇位try {createNode(path);} catch (Exception e) {System.out.println("======== 夺位失败，对皇帝进行监控");try {// 派出小宫女去监视现在的皇帝addZKNodeListener(path);} catch (Exception e1) {e1.printStackTrace();}}}// 不是master就去监听master。派个小宫女去监视皇位private void addZKNodeListener(String path) throws Exception {// 实例化Curator的WatchertreeCache = new TreeCache(client, path);// 启动WatchertreeCache.start();// 添加节点监听treeCache.getListenable().addListener(new TreeCacheListener() {@Overridepublic void childEvent(CuratorFramework client, TreeCacheEvent event) throws Exception {if (event != null && event.getType() == Type.NODE_REMOVED) {System.out.println("======== 皇帝(master)挂了，起义夺权");createNode(path);}}});System.out.println("======== 已经派出间谍监视皇位");}private void createNode(String path) throws Exception {client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).forPath(path);System.out.println("======== 创建节点成功" + serverName + " 成为皇帝");}public String getServerName() {return serverName;}public void setServerName(String serverName) {this.serverName = serverName;}
}

说明：

侵入式tomcat服务器，需要继承ValveBase类，并重写invoke()，需要导入tomcat的jar依赖

运行方式（两个tomcat都要操作）

1. 配置tomcat，在server.xml中添加如下标签

<!-- className是自己编写的类，serverName可以自定义 --><Valve className="ai.zixing.ZkTomcatValve" serverName="tomcat8.5"/>

将项目打成jar包放入tomcat的lib目录下

2. 将项目添加到tomcat中

3. 由于是侵入tomcat方式，所以还需要将zookeeper，Curator等jar包放入tomcat的lib目录下，不然会报错，导致tomcat启动不了。

具体估计需要这几个jar包把，可以根据报错信息找，至于jar怎么找？在你maven仓库找就可以了。

进行测试

分别启动tomcat8.5和tomcat9.0