ZooKeeper配置管理文件

时间：2023-03-09 02:21:27
ZooKeeper配置管理文件

最近在工作中，为了完善公司集群服务的架构，提高可用性，降低运维成本，因此开始学习ZooKeeper。
    至于什么是ZooKeeper？它能做什么？如何安装ZooKeeper？我就不一一介绍了，类似这些资料网上到处都是。我主要是把在开发过程中，以及个人对ZooKeeper的一些了解记录下来，大家如果遇到类似场景时，希望我的文章能够给你提供一些思路。

我使用的ZooKeeper（以下简称：ZK）客户端是Curator Framework，是Apache的项目，它主要的功能是为ZK的客户端使用提供了高可用的封装。在Curator Framework基础上封装的curator-recipes，实现了很多经典场景。比如：集群管理（Leader选举）、共享锁、队列、Counter等等。可以总结Curator主要解决以下三类问题：

  • 封装ZK Client与Server之间的连接处理；
  • 提供了一套Fluent风格的操作API；
  • 提供ZK各种应用场景的抽象封装；

本文主要完成的目标是：Spring PropertyPlaceholderConfigurer配置文件加载器集成ZooKeeper来实现远程配置读取。

配置管理（Configuration Management）。
    在集群服务中，可能都会遇到一个问题：那就是当需要修改配置的时候，必须要对每个实例都进行修改，这是一个很繁琐的事情，并且易出错。当然可以使用脚本来解决，但这不是最好的解决办法。

OK，Let's go！

我们先看看项目结构

ZooKeeper配置管理文件

ZooKeeperPropertyPlaceholderConfigurer.java

继承org.springframework.beans.factory.config.PropertyPlaceholderConfigurer，重写processProperties(beanFactoryToProcess, props)来完成远端配置加载的实现

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package org.bigmouth.common.zookeeper.config.spring;
import java.io.UnsupportedEncodingException;
import java.util.Properties;
import org.apache.commons.lang.StringUtils;
import org.bigmouth.common.zookeeper.config.Config;
import org.bigmouth.common.zookeeper.config.ZooKeeperConfig;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
public class ZooKeeperPropertyPlaceholderConfigurer extends PropertyPlaceholderConfigurer {
     
    public static final String PATH = "zoo.paths";
    @Override
    protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
            throws BeansException {
        super.processProperties(beanFactoryToProcess, props);
         
        try {
            fillCustomProperties(props);
             
            System.out.println(props);
        }
        catch (Exception e) {
            // Ignore
            e.printStackTrace();
        }
    }
    private void fillCustomProperties(Properties props) throws Exception {
        byte[] data = getData(props);
        fillProperties(props, data);
    }
    private void fillProperties(Properties props, byte[] data) throws UnsupportedEncodingException {
        String cfg = new String(data, "UTF-8");
        if (StringUtils.isNotBlank(cfg)) {
            // 完整的应该还需要处理：多条配置、value中包含=、忽略#号开头
            String[] cfgItem = StringUtils.split(cfg, "=");
            props.put(cfgItem[0], cfgItem[1]);
        }
    }
    private byte[] getData(Properties props) throws Exception {
        String path = props.getProperty(PATH);
        Config config = new ZooKeeperConfig();
        return config.getConfig(path);
    }
}

Config.java
配置操作接口

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package org.bigmouth.common.zookeeper.config;
public interface Config {
    byte[] getConfig(String path) throws Exception;
}

Startup.java

程序启动入口

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package org.bigmouth.common.zookeeper.config;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Startup {
    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("classpath:/config/applicationContext.xml");
    }
}

ZooKeeperConfig.java

配置操作接口ZooKeeper的实现

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package org.bigmouth.common.zookeeper.config;
import org.apache.curator.framework.CuratorFramework;
import org.apache.zookeeper.data.Stat;
public class ZooKeeperConfig implements Config {
    @Override
    public byte[] getConfig(String path) throws Exception {
        CuratorFramework client = ZooKeeperFactory.get();
        if (!exists(client, path)) {
            throw new RuntimeException("Path " + path + " does not exists.");
        }
        return client.getData().forPath(path);
    }
     
    private boolean exists(CuratorFramework client, String path) throws Exception {
        Stat stat = client.checkExists().forPath(path);
        return !(stat == null);
    }
}

ZooKeeperFactory.java

管理ZooKeeper客户端连接

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package org.bigmouth.common.zookeeper.config;
import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
public class ZooKeeperFactory {
    public static final String CONNECT_STRING = "172.16.3.42:2181,172.16.3.65:2181,172.16.3.24:2181";
     
    public static final int MAX_RETRIES = 3;
    public static final int BASE_SLEEP_TIMEMS = 3000;
    public static final String NAME_SPACE = "cfg";
    public static CuratorFramework get() {
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(BASE_SLEEP_TIMEMS, MAX_RETRIES);
        CuratorFramework client = CuratorFrameworkFactory.builder()
                .connectString(CONNECT_STRING)
                .retryPolicy(retryPolicy)
                .namespace(NAME_SPACE)
                .build();
        client.start();
        return client;
    }
}

applicationContext.xml

配置加载器使用我们自己创建的ZooKeeperPropertyPlaceholderConfigurer，因为它重写了processProperties方法。这个方法里会去读取远程配置。

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
     
    <bean class="org.bigmouth.common.zookeeper.config.spring.ZooKeeperPropertyPlaceholderConfigurer">
        <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
        <property name="ignoreResourceNotFound" value="true" />
        <property name="locations">
            <list>
                <value>classpath:application.properties</value>
            </list>
        </property>
    </bean>
     
</beans>

application.properties

项目配置文件，里面除了配置ZooKeeper服务器地址和读取的节点以外，其他所有的配置都应该保存在ZooKeeper中。

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zoo.paths=/properties

设置ZooKeeper数据

登录ZooKeeper中为节点 /cfg/properties 添加一条配置项：

ZooKeeper配置管理文件

如图所示：我创建了一个节点 /cfg/properties 并设置内容为：jdbc.driver=org.postgresql.Driver

运行Startup.java

ZooKeeper配置管理文件

OK 了，zoo.paths是本地application.properties文件中的，jdbc.driver是远程ZooKeeper服务器中的。

项目中需要依赖的jar包

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<dependency>
    <groupId>commons-lang</groupId>
    <artifactId>commons-lang</artifactId>
    <version>2.4</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>3.0.3.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>3.0.3.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-tx</artifactId>
    <version>3.0.3.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
    <version>3.0.3.RELEASE</version>
</dependency>
<!-- ZooKeeper -->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-framework</artifactId>
    <version>2.4.2</version>
</dependency>
<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>2.4.2</version>
</dependency>

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