Zookeeper实现参数的集中式管理

Published on: 2017-09-05

点评

虽然现在开源的UCM套件很多，UCM统一配置管理（百度的disconf、阿里的diamond、点评的lion，等很多开源的）。但是很多人是知其然不知其所以然，刚好发现下面这篇文章可以作为原理的教程文章，使用JMS、Redis、Zookeeper简单的实现UCM基本功能，作为学习交流还是很不错的。

文章转自：https://my.oschina.net/OutOfMemory/blog/1503392 作者：@ksfzhaohui

前言

应用项目中都会有一些参数，一般的做法通常可以选择将其存储在本地配置文件或者内存变量中；对于集群机器规模不大、配置变更不是特别频繁的情况下，这两种方式都能很好的解决；但是一旦集群机器规模变大，且配置信息越来越频繁，依靠这两种方式就越来越困难；我们希望能够快速的做到全局参数的变更，因此需要一种参数的集中式管理，下面利用Zookeeper的一些特性来实现简单的参数管理。

准备

jdk:1.7.0_80
zookeeper:3.4.3
curator:2.6.0
spring:3.1.2

Maven引入

Spring相关的jar引入参考上一篇文章

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.3</version>
    <exclusions>
        <exclusion>
            <groupId>com.sun.jmx</groupId>
            <artifactId>jmxri</artifactId>
        </exclusion>
        <exclusion>
            <groupId>com.sun.jdmk</groupId>
            <artifactId>jmxtools</artifactId>
        </exclusion>
        <exclusion>
            <groupId>javax.jms</groupId>
            <artifactId>jms</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>2.6.0</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>2.6.0</version>
</dependency>

目标

可以同时配置监听多个节点如/app1,/app2；
希望只需要配置如/app1，就能够监听其子节点如/app1/modual1以及子节点的子节点如/app1/modual1/xxx/…；
服务器启动能获取当前指定父节点下的所有子节点数据；
在添加节点或者在更新节点数据的时候能够动态通知，这样代码中就能够实时获取最新的数据；
spring配置中可以从Zookeeper中读取参数进行初始化。

实现

提供ZKWatcher类主要用来和Zookeeper建立连接，监听节点，初始化节点数据，更新节点数据，存储节点数据等

1.同时配置监听多个节点提供一个字符串数组给用户用来添加需要监听的节点：

private String[] keyPatterns;

2.能够监听其子节点以及子节点的子节点使用递归的方式用来获取指定监听节点的子节点：

private List<String> listChildren(String path) throws Exception {
    List<String> pathList = new ArrayList<String>();
    pathList.add(path);
    List<String> list = client.getChildren().forPath(path);
    if (list != null && list.size() > 0) {
        for (String cPath : list) {
            String temp = "";
            if ("/".equals(path)) {
                temp = path + cPath;
            } else {
                temp = path + "/" + cPath;
            }
            pathList.addAll(listChildren(temp));
        }
    }
    return pathList;
}

3.服务器启动初始化节点数据上面已经递归获取了所有的节点，所有可以遍历获取所有节点数据，并且存储在Map中：

private Map<String, String> keyValueMap = new ConcurrentHashMap<String, String>();
 
if (pathList != null && pathList.size() > 0) {
    for (String path : pathList) {
        keyValueMap.put(path, readPath(path));
        watcherPath(path);
    }
}
 
private String readPath(String path) throws Exception {
    byte[] buffer = client.getData().forPath(path);
    String value = new String(buffer);
    logger.info("readPath:path = " + path + ",value = " + value);
    return value;
}

4.监听节点数据的变更使用PathChildrenCache用来监听子节点的CHILD_ADDED，CHILD_UPDATED，CHILD_REMOVED事件：

private void watcherPath(String path) {
    PathChildrenCache cache = null;
    try {
        cache = new PathChildrenCache(client, path, true);
        cache.start(StartMode.POST_INITIALIZED_EVENT);
        cache.getListenable().addListener(new PathChildrenCacheListener() {
 
            @Override
            public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {
                switch (event.getType()) {
                case CHILD_ADDED:
                    logger.info("CHILD_ADDED," + event.getData().getPath());
                    watcherPath(event.getData().getPath());
                    keyValueMap.put(event.getData().getPath(), new String(event.getData().getData()));
                    break;
                case CHILD_UPDATED:
                    logger.info("CHILD_UPDATED," + event.getData().getPath());
                    keyValueMap.put(event.getData().getPath(), new String(event.getData().getData()));
                    break;
                case CHILD_REMOVED:
                    logger.info("CHILD_REMOVED," + event.getData().getPath());
                    break;
                default:
                    break;
                }
            }
        });
    } catch (Exception e) {
        if (cache != null) {
            try {
                cache.close();
            } catch (IOException e1) {
            }
        }
        logger.error("watch path error", e);
    }
}

5.spring配置中可以从Zookeeper中读取参数进行初始化实现自定义的PropertyPlaceholderConfigurer类ZKPropPlaceholderConfigurer：

public class ZKPropPlaceholderConfigurer extends PropertyPlaceholderConfigurer {
 
    private ZKWatcher zkwatcher;
 
    @Override
    protected Properties mergeProperties() throws IOException {
        return loadPropFromZK(super.mergeProperties());
    }
 
    /**
     * 从zk中加载配置的常量
     * 
     * @param result
     * @return
     */
    private Properties loadPropFromZK(Properties result) {
        zkwatcher.watcherKeys();
        zkwatcher.fillProperties(result);
        return result;
    }
    ......
}

通过以上的处理，可以使用如下简单的配置来达到目标：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
 
    <bean id="zkwatcher" class="zh.maven.DynamicConf.ZKWatcher">
        <property name="keyPatterns" value="/a2,/a3/m1" />
    </bean>
 
    <bean id="propertyConfigurer" class="zh.maven.DynamicConf.ZKPropPlaceholderConfigurer">
        <property name="zkwatcher" ref="zkwatcher"></property>
    </bean>
 
    <bean id="person" class="zh.maven.DynamicConf.Person">
        <property name="name">
            <value>${/a2/m1}</value>
        </property>
        <property name="address">
            <value>${/a3/m1/v2}</value>
        </property>
        <property name="company">
            <value>${/a3/m1/v2/t2}</value>
        </property>
    </bean>
</beans>

测试

1.首先启动Zookeeper

zkServer.cmd

2.初始化需要使用的节点

public class Create_Node {
 
    static String path = "/a3/m1/v2/t2";
    static CuratorFramework client = CuratorFrameworkFactory.builder()
            .connectString("127.0.0.1:2181").sessionTimeoutMs(5000)
            .retryPolicy(new ExponentialBackoffRetry(1000, 3)).build();
 
    public static void main(String[] args) throws Exception {
        client.start();
        client.create().creatingParentsIfNeeded()
                .withMode(CreateMode.PERSISTENT)
                .forPath(path, "init".getBytes());
    }
}

创建需要的节点方便ZKWatcher来监听，这里根据以上的配置，分别初始化/a3/m1/v2/t2和/a2/m1/v1/t1

3.启动Main，分别验证配置文件中的初始化以及代码动态获取参数

public class Main {
 
    public static void main(String[] args) throws Exception {
        ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "spring-config.xml" });
        Person person = (Person) context.getBean("person");
        System.out.println(person.toString());
 
        ZKWatcher zkwatcher = (ZKWatcher) context.getBean("zkwatcher");
        while (true) {
            Person p = new Person(zkwatcher.getKeyValue("/a2/m1"), zkwatcher.getKeyValue("/a3/m1/v2"),
                    zkwatcher.getKeyValue("/a3/m1/v2/t2"));
            System.out.println(p.toString());
 
            Thread.sleep(1000);
        }
    }
}

4.观察日志同时更新参数：

public class Set_Data {
 
    static String path = "/a3/m1/v2/t2";
    static CuratorFramework client = CuratorFrameworkFactory.builder().connectString("127.0.0.1:2181")
            .sessionTimeoutMs(5000).retryPolicy(new ExponentialBackoffRetry(1000, 3)).build();
 
    public static void main(String[] args) throws Exception {
        client.start();
        Stat stat = new Stat();
        System.out.println(stat.getVersion());
        System.out.println("Success set node for :" + path + ",new version:"
                + client.setData().forPath(path, "codingo_v2".getBytes()).getVersion());
    }
}

部分日志如下：

2017-08-05 18:04:57 - watcher path : [/a2, /a2/m1, /a2/m1/v1, /a2/m1/v1/t2, /a3/m1, /a3/m1/v2, /a3/m1/v2/t2]
2017-08-05 18:04:57 - readPath:path = /a2,value = 
2017-08-05 18:04:57 - readPath:path = /a2/m1,value = zhaohui
2017-08-05 18:04:57 - readPath:path = /a2/m1/v1,value = 
2017-08-05 18:04:57 - readPath:path = /a2/m1/v1/t2,value = init
2017-08-05 18:04:57 - readPath:path = /a3/m1,value = 
2017-08-05 18:04:57 - readPath:path = /a3/m1/v2,value = nanjing
2017-08-05 18:04:57 - readPath:path = /a3/m1/v2/t2,value = codingo_v10
2017-08-05 18:04:57 - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@182f4aea: defining beans [zkwatcher,propertyConfigurer,person]; root of factory hierarchy
name = zhaohui,address = nanjing,company = codingo_v10
name = zhaohui,address = nanjing,company = codingo_v10
2017-08-05 18:04:57 - CHILD_ADDED,/a2/m1
2017-08-05 18:04:57 - CHILD_ADDED,/a3/m1/v2
2017-08-05 18:04:57 - CHILD_ADDED,/a2/m1/v1
2017-08-05 18:04:57 - CHILD_ADDED,/a2/m1/v1/t2
2017-08-05 18:04:57 - CHILD_ADDED,/a3/m1/v2/t2
name = zhaohui,address = nanjing,company = codingo_v10
name = zhaohui,address = nanjing,company = codingo_v10
name = zhaohui,address = nanjing,company = codingo_v10
2017-08-05 18:05:04 - CHILD_UPDATED,/a3/m1/v2/t2
name = zhaohui,address = nanjing,company = codingo_v11
name = zhaohui,address = nanjing,company = codingo_v11

总结

通过Zookeeper实现了一个简单的参数化平台，当然想在生产中使用还有很多需要优化的地方，本文在于提供一个思路；当然除了Zookeeper还可以使用MQ，分布式缓存等来实现参数化平台。

凝雨 - Yun

Zookeeper实现参数的集中式管理

点评

前言

准备

Maven引入

目标

实现

测试

总结

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