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
<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
1、可以同时配置监听多个节点如/app1,/app2；
2、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/…；
3、服务器启动能获取当前指定父节点下的所有子节点数据；
4、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；
5、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>
详细代码svn地址：http://code.taobao.org/svn/temp-pj/DynamicConf
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。
