Sentinel配置动态规则
Sentinel之所以需要配置动态规则，是因为默认情况下，流控、熔断等规则只保存在内存中，一旦客户端重启，规则就全消失了。而动态规则可以将将这些信息持久化到像Nacos、Zookeeper、Apollo等平台中去。一般在生产环境中推荐使用动态规则。
本人在配置动态规则的过程中，碰到了一些坑，然后又解决掉了，现在把它们记录下来，也可以给其他使用Sentinel的人一些参考。
这里测试的是sentinel与dubbo的整合。
一、Sentinel dashboard服务端
因为sentinel dashboard默认是不支持持久化的，所以我们需要这个功能的时候需要自己进行相应的改造，官网上面有一些改造的步骤。
首先在github上下载sentinel的源码，找到sentinel-dashboard的那部分代码
进入com.alibaba.csp.sentinel.dashboard.controller.v2包下，找到FlowControllerV2这个类
将类中的指定的bean替换成zookeeper相关的bean。
再将原来在src/test/java目录下的com.alibaba.csp.sentinel.dashboard.rule.zookeeper包剪切到src/main/java下面去
然后找到main方法，运行dashboard，同时要加上启动参数-Dserver.port=9352 -Dcsp.sentinel.dashboard.server=localhost:9352 -Dproject.name=sentinel-dashboard
启动成功的画面
浏览器上输入http://localhost:9352进入控制台
注意，目前为止，dashboard连接的zookeeper地址是写死在代码中的(如图)，我们需要将它提取到启动参数中，还要做一些修改。
首先，我们找到DashboardConfig这个类，在其中加入以下代码：
/**
* Zookeeper address
*/
public static final String CONFIG_ZK_ADDR = "sentinel.dashboard.zk.addr";
public static String getZkAddr() {
return getConfigStr(CONFIG_ZK_ADDR);
}然后在前面的那个ZookeeperConfig类中，将zookeeper的地址替换掉
然后，在启动参数中加入-Dsentinel.dashboard.zk.addr=192.168.10.15:2181即可指定zookeeper的地址了。
二、Sentinel dashboard客户端
sentinel既可以对dubbo的提供者，也可以对消费者进行流控，不过官网上建议最好对消费者进行流控。本次测试中，sentinel是对于dubbo的消费端进行流量控制。dubbo服务端不需要额外配置，消费端的pom.xml文件需要导入以下内容：
pom.xml
UTF-8
1.6.2
com.alibaba.csp
sentinel-core
${sentinel.version}
com.alibaba.csp
sentinel-transport-simple-http
${sentinel.version}
com.alibaba.csp
sentinel-dubbo-adapter
${sentinel.version}
com.alibaba.csp
sentinel-datasource-zookeeper
${sentinel.version}
com.alibaba.csp
sentinel-datasource-extension
${sentinel.version}
然后启动的时候监听zookeeper的某个节点，并实时同步到流控的规则中。只需要加入以下代码：
//接入zookeeper的规则源
final String remoteAddress = "192.168.10.15:2181";
final String path = "/sentinel_rule_config/com.zhuyun.test.Main";
ReadableDataSource> flowRuleDataSource = new ZookeeperDataSource<>(remoteAddress, path,
source -> JSON.parseObject(source, new TypeReference>() {}));
FlowRuleManager.register2Property(flowRuleDataSource.getProperty()); 当然，其中的变量可以写成配置文件或者启动参数的形式，这里就不演示了。
接下来，分别启动dubbo的提供者与消费者，然后在sentinel-dashboard控制台上可以看到他们了。
接下来我们在控制台上设置流控规则，对run()这个方法进行限速
限速后，再来看看统计的结果
run()方法已经限制成功了，另一个方法依然是原来的速度。
而且，在zookeeper中，也已经存在了该条规则，下次重启的时候规则仍然在。
三、遇到的坑
下面是调试过程中遇到过的一些坑。
1、pom.xml
org.apache.curator
curator-recipes
${curator.version}
刚开始将test中的zookeeper包拷贝到main下运行的时候，出现了以下的错误
java.lang.IllegalStateException: Error processing condition on org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration.propertySourcesPlaceholderConfigurer
at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:64) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.context.annotation.ConditionEvaluator.shouldSkip(ConditionEvaluator.java:108) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForBeanMethod(ConfigurationClassBeanDefinitionReader.java:180) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitionsForConfigurationClass(ConfigurationClassBeanDefinitionReader.java:141) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.loadBeanDefinitions(ConfigurationClassBeanDefinitionReader.java:117) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:328) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:233) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanDefinitionRegistryPostProcessors(PostProcessorRegistrationDelegate.java:271) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:91) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:694) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:532) ~[spring-context-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:780) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:333) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1277) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1265) [spring-boot-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at com.alibaba.csp.sentinel.dashboard.DashboardApplication.main(DashboardApplication.java:33) [classes/:na]
Caused by: java.lang.IllegalStateException: Failed to introspect Class [com.alibaba.csp.sentinel.dashboard.rule.zookeeper.ZookeeperConfig] from ClassLoader [sun.misc.Launcher$AppClassLoader@2a139a55]
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:659) ~[spring-core-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:556) ~[spring-core-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.util.ReflectionUtils.doWithMethods(ReflectionUtils.java:541) ~[spring-core-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.util.ReflectionUtils.getUniqueDeclaredMethods(ReflectionUtils.java:599) ~[spring-core-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:718) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:659) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:627) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1489) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1012) ~[spring-beans-5.0.9.RELEASE.jar:5.0.9.RELEASE]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanTypeForNonAliasDefinition(BeanTypeRegistry.java:194) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanTypeForNonAliasDefinition(BeanTypeRegistry.java:170) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.addBeanType(BeanTypeRegistry.java:163) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.lambda$updateTypesIfNecessary$2(BeanTypeRegistry.java:150) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at java.util.Iterator.forEachRemaining(Iterator.java:116) ~[na:1.8.0_91]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.updateTypesIfNecessary(BeanTypeRegistry.java:148) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.BeanTypeRegistry.getNamesForType(BeanTypeRegistry.java:114) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.collectBeanNamesForType(OnBeanCondition.java:265) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getBeanNamesForType(OnBeanCondition.java:254) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchingBeans(OnBeanCondition.java:196) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.OnBeanCondition.getMatchOutcome(OnBeanCondition.java:116) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ~[spring-boot-autoconfigure-2.0.5.RELEASE.jar:2.0.5.RELEASE]
... 17 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/apache/curator/RetryPolicy
at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_91]
at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_91]
at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_91]
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:641) ~[spring-core-5.0.9.RELEASE.jar:5.0.9.RELEASE]
... 37 common frames omitted
Caused by: java.lang.ClassNotFoundException: org.apache.curator.RetryPolicy
at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_91]
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) ~[na:1.8.0_91]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_91]
... 41 common frames omitted后来发现是zookeeper的依赖包中有
2、/v2/flow 浏览器缓存
在改造成功之前，在浏览器中访问过了很多次http://localhost:9352，进入到“流控规则”界面时，url本来应该是这样的
但是实际上我每次进入这个界面时，url是这样的：
其中少了一个/v2，我还一直以为是我的配置有问题，找了很久的原因，后来换了一个浏览器就好了，才知道是缓存导致的。看来以后用到浏览器测试的时候，一定要多想想缓存的问题。