简介

使用背景

说到配置中心，目前市面上用的较多的配置中心都广为人知，比如百度的Disconf、Spring Cloud Config、携程的Apollo、阿里的Nacos等。由于项目组一直是使用的zookeeper作为配置中心，所以来学习使用。

实现原理

在Zookeeper建立一个根节点，比如/CONFIG，代表某个配置文件。将配置文件中的信息作为根节点的子节点存储，比如配置项timeout=3000，在Zookeeper中展现为：/CONFIG/timeout
，节点内容是3000。然后让所有使用到该配置信息的应用机器集成Zookeeper并监控/CONFIG的状态，一旦配置信息也就是子节点发生变化，每台应用机器就会收到ZK的通知，然后从ZK中获取新的配置信息应用到系统中。
实现原理细节可参考：https://cloud.tencent.com/developer/news/365803

Spring Boot整合Zookeeper

引入依赖

		 <dependency><groupId>org.apache.curator</groupId><artifactId>curator-recipes</artifactId><version>4.3.0</version></dependency>

Curator是Apache软件基金会下的一个开源框架，目前是Apache下的顶级项目。Curator是ZooKeeper的一个Java客户端库，包括一个高层API框架和一些实用程序，使得开发人员在使用ZooKeeper时更容易，更可靠。
参考：https://blog.csdn.net/hzygcs/article/details/88171620

修改配置application.properties

由于只是简单使用，配置连接即可

zookeeper.url=192.168.1.106:2181

定义配置类

ZookeeperConfig.java

@Configuration
public class ZookeeperConfig {Properties properties = new Properties();//可以理解curatorFramework为客户端，基本操作都由它完成CuratorFramework curatorFramework = null;TreeCache treeCache = null;@Value("${zookeeper.url}")private String zkUrl;//定义顶级private final String CONFIG_NAME = "/zookeeper";//初始化private void init() {RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);curatorFramework = CuratorFrameworkFactory.newClient(zkUrl, retryPolicy);treeCache = new TreeCache(curatorFramework, CONFIG_NAME);}/*** 设置属性* @param key* @param value* @throws Exception*/public void setProperties(String key, String value) throws Exception {String propertiesKey = CONFIG_NAME + "/" + key;Stat stat = curatorFramework.checkExists().forPath(propertiesKey);if(stat == null) {curatorFramework.create().forPath(propertiesKey);}curatorFramework.setData().forPath(propertiesKey, value.getBytes());}/*** 获取属性* @param key* @return*/public String getProperties(String key) {return properties.getProperty(key);}@PostConstructpublic void loadProperties() {try {init();curatorFramework.start();treeCache.start();// 从zk中获取配置放入本地配置中Stat stat = curatorFramework.checkExists().forPath(CONFIG_NAME);if(stat == null) {curatorFramework.create().forPath(CONFIG_NAME);}List<String> configList = curatorFramework.getChildren().forPath(CONFIG_NAME);for (String configName : configList) {byte[] value = curatorFramework.getData().forPath(CONFIG_NAME + "/" + configName);properties.setProperty(configName, new String(value));}// 监听属性值变更treeCache.getListenable().addListener(new TreeCacheListener() {@Overridepublic void childEvent(CuratorFramework curatorFramework, TreeCacheEvent treeCacheEvent) throws Exception {if (Objects.equals(treeCacheEvent.getType(), TreeCacheEvent.Type.NODE_ADDED) ||Objects.equals(treeCacheEvent.getType(), TreeCacheEvent.Type.NODE_UPDATED)) {String updateKey = treeCacheEvent.getData().getPath().replace(CONFIG_NAME + "/", "");properties.setProperty(updateKey, new String(treeCacheEvent.getData().getData()));System.out.println("数据更新: "+treeCacheEvent.getType()+", key:"+updateKey+",value:"+new String(treeCacheEvent.getData().getData()));}}});} catch (Exception e) {e.printStackTrace();}}}

配置测试接口

ZkController.java

@RestController
public class ZkController {@Autowiredprivate ZookeeperConfig zookeeperConfig;@GetMapping("get/{key}")public String getProperties(@PathVariable String key) {return zookeeperConfig.getProperties(key);}@GetMapping("set/{key}/{value}")public String setProperties(@PathVariable String key, @PathVariable String value) throws Exception {zookeeperConfig.setProperties(key, value);return "配置成功";}
}

验证

zookeeper节点情况如下：

浏览器中输入：http://localhost:8080/get/hehe 可以获取到，使用工具对其他两个node进行更新，程序控制台也可以查看到更新数据信息：

当验证set的时候，程序报错：

org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for /zookeeper/123at org.apache.zookeeper.KeeperException.create(KeeperException.java:106) ~[zookeeper-3.5.7.jar:3.5.7]at org.apache.zookeeper.KeeperException.create(KeeperException.java:54) ~[zookeeper-3.5.7.jar:3.5.7]at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:1637) ~[zookeeper-3.5.7.jar:3.5.7]at org.apache.curator.framework.imps.CreateBuilderImpl$17.call(CreateBuilderImpl.java:1180) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.framework.imps.CreateBuilderImpl$17.call(CreateBuilderImpl.java:1156) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.connection.StandardConnectionHandlingPolicy.callWithRetry(StandardConnectionHandlingPolicy.java:67) ~[curator-client-4.3.0.jar:na]at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:81) ~[curator-client-4.3.0.jar:na]at org.apache.curator.framework.imps.CreateBuilderImpl.pathInForeground(CreateBuilderImpl.java:1153) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.framework.imps.CreateBuilderImpl.protectedPathInForeground(CreateBuilderImpl.java:607) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:597) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:575) ~[curator-framework-4.3.0.jar:4.3.0]at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:51) ~[curator-framework-4.3.0.jar:4.3.0]at com.springboot.springbootzookeeper.config.ZookeeperConfig.setProperties(ZookeeperConfig.java:55) ~[classes/:na]at com.springboot.springbootzookeeper.controller.ZkController.setProperties(ZkController.java:28) ~[classes/:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_101]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_101]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_101]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_101]at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.6.RELEASE.jar:5.2.6.RELEASE]at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.6.RELEASE.jar:5.2.6.RELEASE]at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) [tomcat-embed-core-9.0.35.jar:9.0.35]at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.35.jar:9.0.35]at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_101]at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_101]at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.35.jar:9.0.35]at java.lang.Thread.run(Thread.java:745) [na:1.8.0_101]2020-06-29 16:57:18.173  INFO 13664 --- [168.1.106:2181)] org.apache.zookeeper.ClientCnxn          : Unable to read additional data from server sessionid 0x10000654e3b001a, likely server has closed socket, closing socket connection and attempting reconnect
2020-06-29 16:57:18.273  INFO 13664 --- [ain-EventThread] o.a.c.f.state.ConnectionStateManager     : State change: SUSPENDED

感谢
https://blog.csdn.net/forget_me_not1991/article/details/80902055
https://www.jianshu.com/p/57ac51e9987f

将curator-recipes版本调整为2.8.0后，可以将节点添加成功。

2020-06-29 17:07:11.622  INFO 14628 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-06-29 17:07:11.625  INFO 14628 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 3 ms
数据更新: NODE_ADDED, key:123,value:192.168.137.1
数据更新: NODE_UPDATED, key:123,value:123