1、客户端API操作
1.1 IDEA 环境搭建
前提：保证 hadoop102、hadoop103、hadoop104 服务器上 Zookeeper 集群服务端启动。
1、创建一个工程：Zookeeper
2、添加pom文件
<?xml version="1.0" encoding="UTF-8"?> <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/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>org.example</groupId> <artifactId>Zookeeper</artifactId> <version>1.0-SNAPSHOT</version> <properties> <maven.compiler.source>8</maven.compiler.source> <maven.compiler.target>8</maven.compiler.target> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>RELEASE</version> </dependency> <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-core</artifactId> <version>2.8.2</version> </dependency> <dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.5.7</version> </dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-framework</artifactId> <version>4.3.0</version> </dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-recipes</artifactId> <version>4.3.0</version> </dependency> <dependency> <groupId>org.apache.curator</groupId> <artifactId>curator-client</artifactId> <version>4.3.0</version> </dependency> </dependencies> </project>
3、拷贝log4j.properties文件到项目根目录
需要在项目的 src/main/resources 目录下，新建一个文件，命名为“log4j.properties”，在文件中填入。
log4j.rootLogger=INFO, stdout log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n log4j.appender.logfile=org.apache.log4j.FileAppender log4j.appender.logfile.File=target/spring.log log4j.appender.logfile.layout=org.apache.log4j.PatternLayout log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n
4、创建包名com.example.zk
5、创建类名称zkClient
1.2 创建Zookeeper客户端
// 注意：逗号前后不能有空格 private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private static int sessionTimeout = 2000; private ZooKeeper zkClient = null; @Before public void init() throws Exception { zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent watchedEvent) { // 收到事件通知后的回调函数（用户的业务逻辑） System.out.println(watchedEvent.getType() + "--" + watchedEvent.getPath()); // 再次启动监听 try { List<String> children = zkClient.getChildren("/", true); for (String child : children) { System.out.println(child); } } catch (Exception e) { e.printStackTrace(); } } }); } }
1.3 创建子节点
// 创建子节点 @Test public void create() throws Exception { // 参数 1：要创建的节点的路径； 参数 2：节点数据 ； 参数 3：节点权限 ； 参数 4：节点的类型 String nodeCreated = zkClient.create("/atguigu", "shuaige".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); }
1.4 获取子节点并监听节点变化
// 获取子节点 @Test public void getChildren() throws Exception { List<String> children = zkClient.getChildren("/", true); for (String child : children) { System.out.println(child); } // 延时阻塞 Thread.sleep(Long.MAX_VALUE); }
1.5 判断 Znode 是否存在
// 判断 znode 是否存在 @Test public void exist() throws Exception { Stat stat = zkClient.exists("/atguigu", false); System.out.println(stat == null ? "not exist" : "exist"); }
2、客户端向服务端写数据流程
1、写流程之写入请求直接发送给Leader节点
2、写流程之写入请求发送给follower节点
