# DiscoveryAgent **Repository Path**: jacksonsmart/DiscoveryAgent ## Basic Information - **Project Name**: DiscoveryAgent - **Description**: ☀️ Nepxion Discovery Agent is a java agent to resolve loss of ThreadLocal in cross-thread scenario, such as Spring Async、Hystrix Thread、Runnable、Callable、Single Thread、Thread Pool、MDC 异步跨线程Agent - **Primary Language**: Java - **License**: Apache-2.0 - **Default Branch**: master - **Homepage**: http://www.nepxion.com - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 38 - **Created**: 2021-03-25 - **Last Updated**: 2021-11-03 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README [^_^]: ![](http://nepxion.gitee.io/discovery/docs/discovery-doc/Cover.jpg) ![](http://nepxion.gitee.io/discovery/docs/discovery-doc/Banner.png) # Discovery【探索】微服务企业级解决方案 [![Total lines](https://tokei.rs/b1/github/Nepxion/Discovery?category=lines)](https://tokei.rs/b1/github/Nepxion/Discovery?category=lines) [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg?label=license)](https://github.com/Nepxion/Discovery/blob/6.x.x/LICENSE) [![Maven Central](https://img.shields.io/maven-central/v/com.nepxion/discovery.svg?label=maven%20central)](https://search.maven.org/artifact/com.nepxion/discovery) [![Javadocs](http://www.javadoc.io/badge/com.nepxion/discovery-plugin-framework-starter.svg)](http://www.javadoc.io/doc/com.nepxion/discovery-plugin-framework-starter) [![Build Status](https://travis-ci.org/Nepxion/Discovery.svg?branch=6.x.x)](https://travis-ci.org/Nepxion/Discovery) [![Codacy Badge](https://api.codacy.com/project/badge/Grade/8e39a24e1be740c58b83fb81763ba317)](https://www.codacy.com/project/HaojunRen/Discovery/dashboard?utm_source=github.com&utm_medium=referral&utm_content=Nepxion/Discovery&utm_campaign=Badge_Grade_Dashboard) [![Stars](https://img.shields.io/github/stars/Nepxion/Discovery.svg?label=Stars&tyle=flat&logo=GitHub)](https://github.com/Nepxion/Discovery/stargazers) [![Stars](https://gitee.com/Nepxion/Discovery/badge/star.svg?theme=gvp)](https://gitee.com/nepxion/Discovery/stargazers) [![Spring Boot](https://img.shields.io/maven-central/v/org.springframework.boot/spring-boot-dependencies.svg?label=Spring%20Boot&logo=Spring)](https://search.maven.org/artifact/org.springframework.boot/spring-boot-dependencies) [![Spring Cloud](https://img.shields.io/maven-central/v/org.springframework.cloud/spring-cloud-dependencies.svg?label=Spring%20Cloud&logo=Spring)](https://search.maven.org/artifact/org.springframework.cloud/spring-cloud-dependencies) [![Spring Cloud Alibaba](https://img.shields.io/maven-central/v/com.alibaba.cloud/spring-cloud-alibaba-dependencies.svg?label=Spring%20Cloud%20Alibaba&logo=Spring)](https://search.maven.org/artifact/com.alibaba.cloud/spring-cloud-alibaba-dependencies) [![Nepxion Discovery](https://img.shields.io/maven-central/v/com.nepxion/discovery.svg?label=Nepxion%20Discovery&logo=Anaconda)](https://search.maven.org/artifact/com.nepxion/discovery) [![Discovery DOC PPT](https://img.shields.io/badge/Discovery%20Doc-PPT-brightgreen?logo=Microsoft%20PowerPoint)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-ppt.html) [![Discovery DOC PDF](https://img.shields.io/badge/Discovery%20Doc-PDF-brightgreen?logo=Adobe%20Acrobat%20Reader)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-pdf.html) [![Discovery DOC HTML](https://img.shields.io/badge/Discovery%20Doc-HTML-brightgreen?logo=Microsoft%20Edge)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-html.html) 如果您觉得本框架具有一定的参考价值和借鉴意义，请帮忙在页面右上角 [**Star**] ![](http://nepxion.gitee.io/discovery/docs/icon-doc/star1.png) 首席作者简介 - Nepxion开源社区创始人 - 2020年阿里巴巴中国云原生峰会出品人 - 2020年被Nacos和Spring Cloud Alibaba纳入相关开源项目 - 2021年阿里巴巴技术峰会上海站演讲嘉宾 - 2021年荣获陆奇博士主持的奇绩资本，进行风险投资的关注和调研 - 2021年入选Gitee最有价值开源项目 - Nacos Group Member、Spring Cloud Alibaba Member - Spring Cloud Alibaba、Nacos、Sentinel、OpenTracing Committer & Contributor NacosNacosSpring Cloud Alibaba ![](http://nepxion.gitee.io/discovery/docs/icon-doc/star4.png) 商业化合作 ① Discovery系列 | 框架名称 | 框架版本 | 支持Spring Cloud版本 | 使用许可 | | --- | --- | --- | --- | | Discovery | 1.x.x ~ 6.x.x | Camden ~ Hoxton | 开源，永久免费 | | DiscoveryX | 7.x.x | 202x | 闭源，商业许可 | ② Polaris系列 Polaris为Discovery高级定制版，特色功能 - 基于Nepxion Discovery集成定制 - 多云、多活、多机房流量调配 - 跨云动态域名、跨环境适配 - DCN、DSU、SET单元化部署 - 组件灵活装配、配置对外屏蔽 - 极简低代码PaaS平台 | 框架名称 | 框架版本 | 支持Discovery版本 | 支持Spring Cloud版本 | 使用许可 | | --- | --- | --- | --- | --- | | Polaris | 1.x.x | 6.x.x | Finchley ~ Hoxton | 闭源，商业许可 | | Polaris | 2.x.x | 7.x.x | 202x | 闭源，商业许可 | 有商业版需求的企业和用户，请添加微信1394997，联系作者，洽谈合作事宜 ![](http://nepxion.gitee.io/discovery/docs/discovery-doc/Logo64.png) Discovery【探索】微服务企业级解决方案 ① Discovery【探索】微服务企业级解决方案文档 - [Discovery【探索】微服务企业级解决方案(WIKI版)](http://nepxion.com/discovery) - [Discovery【探索】微服务企业级解决方案(PPT版)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-ppt.html) - [Discovery【探索】微服务企业级解决方案(PDF版)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-pdf.html) - [Discovery【探索】微服务企业级解决方案(HTML版)](http://nepxion.gitee.io/discovery/docs/link-doc/discovery-html.html) ② Discovery【探索】微服务企业级解决方案源码。请访问Gitee镜像获得最佳体验 - [源码Gitee同步镜像](https://gitee.com/Nepxion/Discovery) - [源码Github原镜像](https://github.com/Nepxion/Discovery) ③ Discovery【探索】微服务企业级解决方案指南示例源码。请访问Gitee镜像获得最佳体验 - [指南Gitee同步镜像](https://gitee.com/Nepxion/DiscoveryGuide) - [指南Github原镜像](https://github.com/Nepxion/DiscoveryGuide) ④ Discovery【探索】微服务企业级解决方案指南示例说明 - 对于入门级玩家，参考[6.x.x指南示例极简版](https://github.com/Nepxion/DiscoveryGuide/tree/6.x.x-simple)，分支为6.x.x-simple - 对于熟练级玩家，参考[6.x.x指南示例精进版](https://github.com/Nepxion/DiscoveryGuide/tree/6.x.x)，分支为6.x.x。除上述《极简版》功能外，涉及到指南篇里的绝大多数高级功能 - 对于骨灰级玩家，参考[6.x.x指南示例高级版](https://github.com/Nepxion/DiscoveryGuide/tree/6.x.x-complex)，分支为6.x.x-complex。除上述《精进版》功能外，涉及到指南篇里的ActiveMQ、MongoDB、RabbitMQ、Redis、RocketMQ、MySQL等高级调用链和蓝绿灰度调用链的整合 - 上述指南实例分支是针对Spring Cloud旧版本。对于Spring Cloud 202x版本，参考[202x版指南示例精进版](https://github.com/Nepxion/DiscoveryGuide/tree/master)，分支为master ⑤ Discovery【探索】微服务企业级解决方案快速入门文档 - [Gitee Wiki](https://gitee.com/nepxion/Discovery/wikis/pages) - [Github Wiki](https://github.com/Nepxion/Discovery/wiki) ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/Logo64.png) Polaris【北极星】企业级云原生微服务框架 ① Polaris【北极星】企业级云原生微服务框架文档 - [Polaris【北极星】企业级云原生微服务框架(WIKI版)](http://nepxion.com/polaris) - [Polaris【北极星】企业级云原生微服务框架(PDF版)](http://nepxion.gitee.io/discovery/docs/link-doc/polaris-pdf.html) - [Polaris【北极星】企业级云原生微服务框架(HTML版)](http://nepxion.gitee.io/discovery/docs/link-doc/polaris-html.html) ② Polaris【北极星】企业级云原生微服务框架源码。请访问Gitee镜像获得最佳体验 - [源码Gitee同步镜像](https://gitee.com/polaris-paas/polaris-sdk) - [源码Github原镜像](https://github.com/polaris-paas/polaris-sdk) ③ Polaris【北极星】企业级云原生微服务框架指南示例源码。请访问Gitee镜像获得最佳体验 - [指南Gitee同步镜像](https://gitee.com/polaris-paas/polaris-guide) - [指南Github原镜像](https://github.com/polaris-paas/polaris-guide) ④ Polaris【北极星】企业级云原生微服务框架指南示例说明 - Spring Cloud旧版本，参考[1.x.x指南示例](https://github.com/polaris-paas/polaris-guide/tree/1.x.x)，分支为1.x.x - Spring Cloud新版本，参考[2.x.x指南示例](https://github.com/polaris-paas/polaris-guide/tree/master)，分支为master ![](http://nepxion.gitee.io/discovery/docs/icon-doc/Logo64.png) Discovery【探索】和Polaris【北极星】架构体系 ① Discovery【探索】和Polaris【北极星】联合架构图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/Architecture.jpg) ② Discovery【探索】和Polaris【北极星】联合拓扑图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/Topology.jpg) ③ Polaris【北极星】分层架构图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/Layer.jpg) ④ Discovery【探索】实施方案图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/All.jpg) ⑤ Discovery【探索】域网关实施图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/DomainEnable.jpg) ⑥ Discovery【探索】非域网关实施图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/DomainDisable.jpg) ⑦ Discovery【探索】全局订阅实施图 ![](http://nepxion.gitee.io/discovery/docs/polaris-doc/GlobalSub.jpg) ## 异步场景下Discovery和DiscoveryAgent Discovery框架存在着如下全链路传递上下文的场景，包括 - 策略路由Header全链路从网关传递到服务 - 调用链埋点全链路从网关传递到服务 - 业务自定义的上下文的传递 上述上下文会在如下异步场景中丢失，包括 - WebFlux Reactor响应式异步 - Spring异步，@Async注解异步 - Hystrix线程池隔离模式异步 - 线程，线程池异步 - SLF4J日志异步 通过DiscoveryAgent，解决上述痛点。Discovery框架利用DiscoveryAgent字节码增强技术，完美解决各种调用场景下的异步，包括 - Spring Cloud Gateway过滤器中的上下文传递 - Zuul过滤器中的上下文传递 - Feign拦截器中的上下文转发 - RestTemplate拦截器中的上下文转发 - WebClient拦截器中的上下文转发 ### 异步场景下DiscoveryAgent解决方案 ![](http://nepxion.gitee.io/discovery/docs/icon-doc/information.png) DiscoveryAgent不仅适用于Discovery框架，也适用于一切具有类似使用场景的基础框架（例如：Dubbo）和业务系统 ThreadLocal的作用是提供线程内的局部变量，在多线程环境下访问时能保证各个线程内的ThreadLocal变量各自独立。在异步场景下，由于出现线程切换的问题，例如，主线程切换到子线程，会导致线程ThreadLocal上下文丢失。DiscoveryAgent通过Java Agent方式解决这些痛点 涵盖所有Java框架的异步场景，解决如下8个异步场景下丢失线程ThreadLocal上下文的问题 - WebFlux Reactor - `@`Async - Hystrix Thread Pool Isolation - Runnable - Callable - Single Thread - Thread Pool - SLF4J MDC #### 异步跨线程DiscoveryAgent获取 插件获取方式有两种方式 - 通过[https://github.com/Nepxion/DiscoveryAgent/releases](https://github.com/Nepxion/DiscoveryAgent/releases)下载最新版本的Discovery Agent - 编译[https://github.com/Nepxion/DiscoveryAgent](https://github.com/Nepxion/DiscoveryAgent)产生discovery-agent目录 #### 异步跨线程DiscoveryAgent清单 ① discovery-agent-starter-`$`{discovery.version}.jar为Agent引导启动程序，JVM启动时进行加载 ② agent.config为基准扫描目录配置文件 绝大多数情况下不需要修改，当然使用者也可以增加和删除agent.config的基准扫描目录。默认配置如下 ``` # Base thread scan packages agent.plugin.thread.scan.packages=reactor.core.publisher;org.springframework.aop.interceptor;com.netflix.hystrix ``` 基准扫描目录，含义如下 - WebFlux Reactor异步场景下的扫描目录对应为reactor.core.publisher - `@`Async场景下的扫描目录对应为org.springframework.aop.interceptor - Hystrix线程池隔离场景下的扫描目录对应为com.netflix.hystrix ③ plugin/discovery-agent-starter-plugin-strategy-`$`{discovery.version}.jar插件，解决Nepxion Discovery上下文异步场景 ④ plugin/discovery-agent-starter-plugin-mdc-`$`{discovery.version}.jar插件，解决SLF4J MDC日志上下文异步场景 ⑤ 业务系统可以自定义plugin，解决业务自己定义的上下文异步场景 #### 异步跨线程DiscoveryAgent使用 ① 使用示例 - 通过如下-javaagent启动，基本格式，如下 ``` -javaagent:C:/opt/discovery-agent/discovery-agent-starter-${discovery.agent.version}.jar -Dthread.scan.packages=com.nepxion.discovery.guide.service.feign ``` ② 参数说明 - C:/opt/discovery-agent：Agent所在的目录，需要对应到实际的目录上 - `-D`thread.scan.packages：Runnable/Callable/Thread/ThreadPool等异步类所在的扫描目录，该目录下的异步类都会被装饰 - 扫描目录最好精细和准确，目录越详细，越可以减少被装饰的对象数，从一定程度上可以提高性能 - 扫描目录如果有多个，用“;”分隔 - 扫描目录如果含有“;”，可能会在某些操作系统中无法被识别，请用`""`进行引入，例如，-Dthread.scan.packages="com.abc;com.xyz" - 扫描目录下没有Runnable/Callable/Thread/ThreadPool等异步类存在，那么thread.scan.packages也不需要配置，最终启动命令行简化为-javaagent:C:/opt/discovery-agent/discovery-agent-starter-${discovery.agent.version}.jar - `-D`thread.gateway.enabled：Spring Cloud Gateway端策略Header输出到异步子线程。默认开启 - `-D`thread.zuul.enabled：Zuul端策略Header输出到异步子线程。默认开启 - `-D`thread.service.enabled：服务端策略Header输出到异步子线程。默认开启 - `-D`thread.mdc.enabled：SLF4J MDC日志输出到异步子线程。默认开启 - `-D`thread.request.decorator.enabled：异步调用场景下在服务端的Request请求的装饰，当主线程先于子线程执行完的时候，Request会被Destory，导致Header仍旧拿不到，开启装饰，就可以确保拿到。默认为开启，根据实践经验，大多数场景下，需要开启该开关 #### 异步跨线程DiscoveryAgent扩展 - 根据规范开发一个插件，插件提供了钩子函数，在某个类被加载的时候，可以注册一个事件到线程上下文切换事件当中，实现业务自定义ThreadLocal的跨线程传递 - plugin目录为放置需要在线程切换时进行ThreadLocal传递的自定义插件。业务自定义插件开发完后，放入到plugin目录下即可 具体步骤介绍，如下 ① SDK侧工作 - 新建ThreadLocal上下文类 ```java public class MyContext { private static final ThreadLocal THREAD_LOCAL = new ThreadLocal() { @Override protected MyContext initialValue() { return new MyContext(); } }; public static MyContext getCurrentContext() { return THREAD_LOCAL.get(); } public static void clearCurrentContext() { THREAD_LOCAL.remove(); } private Map attributes = new HashMap<>(); public Map getAttributes() { return attributes; } public void setAttributes(Map attributes) { this.attributes = attributes; } } ``` ② Agent侧工作 - 新建一个模块，引入如下依赖 ```xml com.nepxion discovery-agent-starter ${discovery.agent.version} provided ``` - 新建一个ThreadLocalHook类继承AbstractThreadLocalHook ```java public class MyContextHook extends AbstractThreadLocalHook { @Override public Object create() { // 从主线程的ThreadLocal里获取并返回上下文对象 return MyContext.getCurrentContext().getAttributes(); } @Override public void before(Object object) { // 把create方法里获取到的上下文对象放置到子线程的ThreadLocal里 if (object instanceof Map) { MyContext.getCurrentContext().setAttributes((Map) object); } } @Override public void after() { // 线程结束，销毁上下文对象 MyContext.clearCurrentContext(); } } ``` - 新建一个Plugin类继承AbstractPlugin ```java public class MyContextPlugin extends AbstractPlugin { private Boolean threadMyPluginEnabled = Boolean.valueOf(System.getProperty("thread.myplugin.enabled", "false")); @Override protected String getMatcherClassName() { // 返回存储ThreadLocal对象的类名，由于插件是可以插拔的，所以必须是字符串形式，不允许是显式引入类 return "com.nepxion.discovery.example.sdk.MyContext"; } @Override protected String getHookClassName() { // 返回ThreadLocalHook类名 return MyContextHook.class.getName(); } @Override protected boolean isEnabled() { // 通过外部-Dthread.myplugin.enabled=true/false的运行参数来控制当前Plugin是否生效。该方法在父类中定义的返回值为true，即缺省为生效 return threadMyPluginEnabled; } } ``` - 定义SPI扩展，在src/main/resources/META-INF/services目录下定义SPI文件 名称为固定如下格式 ``` com.nepxion.discovery.agent.plugin.Plugin ``` 内容为Plugin类的全路径 ``` com.nepxion.discovery.example.agent.MyContextPlugin ``` - 执行Maven编译，把编译后的包放在discovery-agent/plugin目录下 - 给服务增加启动参数并启动，如下 ``` -javaagent:C:/opt/discovery-agent/discovery-agent-starter-${discovery.agent.version}.jar -Dthread.scan.packages=com.nepxion.discovery.example.application -Dthread.myplugin.enabled=true ``` ③ Application侧工作 - 执行MyApplication，它模拟在主线程ThreadLocal放入Map数据，子线程通过DiscoveryAgent获取到该Map数据，并打印出来 ```java @SpringBootApplication @RestController public class MyApplication { private static final Logger LOG = LoggerFactory.getLogger(MyApplication.class); public static void main(String[] args) { SpringApplication.run(MyApplication.class, args); invoke(); } public static void invoke() { RestTemplate restTemplate = new RestTemplate(); for (int i = 1; i <= 10; i++) { restTemplate.getForEntity("http://localhost:8080/index/" + i, String.class).getBody(); } } @GetMapping("/index/{value}") public String index(@PathVariable(value = "value") String value) throws InterruptedException { Map attributes = new HashMap(); attributes.put(value, "MyContext"); MyContext.getCurrentContext().setAttributes(attributes); LOG.info("【主】线程ThreadLocal：{}", MyContext.getCurrentContext().getAttributes()); new Thread(new Runnable() { @Override public void run() { LOG.info("【子】线程ThreadLocal：{}", MyContext.getCurrentContext().getAttributes()); try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } LOG.info("Sleep 5秒之后，【子】线程ThreadLocal：{} ", MyContext.getCurrentContext().getAttributes()); } }).start(); return ""; } } ``` 输出结果，如下 ``` 2020-11-09 00:08:14.330 INFO 16588 --- [nio-8080-exec-1] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{1=MyContext} 2020-11-09 00:08:14.381 INFO 16588 --- [ Thread-4] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{1=MyContext} 2020-11-09 00:08:14.402 INFO 16588 --- [nio-8080-exec-2] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{2=MyContext} 2020-11-09 00:08:14.403 INFO 16588 --- [ Thread-5] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{2=MyContext} 2020-11-09 00:08:14.405 INFO 16588 --- [nio-8080-exec-3] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{3=MyContext} 2020-11-09 00:08:14.406 INFO 16588 --- [ Thread-6] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{3=MyContext} 2020-11-09 00:08:14.414 INFO 16588 --- [nio-8080-exec-4] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{4=MyContext} 2020-11-09 00:08:14.414 INFO 16588 --- [ Thread-7] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{4=MyContext} 2020-11-09 00:08:14.417 INFO 16588 --- [nio-8080-exec-5] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{5=MyContext} 2020-11-09 00:08:14.418 INFO 16588 --- [ Thread-8] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{5=MyContext} 2020-11-09 00:08:14.421 INFO 16588 --- [nio-8080-exec-6] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{6=MyContext} 2020-11-09 00:08:14.422 INFO 16588 --- [ Thread-9] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{6=MyContext} 2020-11-09 00:08:14.424 INFO 16588 --- [nio-8080-exec-7] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{7=MyContext} 2020-11-09 00:08:14.425 INFO 16588 --- [ Thread-10] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{7=MyContext} 2020-11-09 00:08:14.427 INFO 16588 --- [nio-8080-exec-8] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{8=MyContext} 2020-11-09 00:08:14.428 INFO 16588 --- [ Thread-11] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{8=MyContext} 2020-11-09 00:08:14.430 INFO 16588 --- [nio-8080-exec-9] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{9=MyContext} 2020-11-09 00:08:14.431 INFO 16588 --- [ Thread-12] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{9=MyContext} 2020-11-09 00:08:14.433 INFO 16588 --- [io-8080-exec-10] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{10=MyContext} 2020-11-09 00:08:14.434 INFO 16588 --- [ Thread-13] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{10=MyContext} 2020-11-09 00:08:19.382 INFO 16588 --- [ Thread-4] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{1=MyContext} 2020-11-09 00:08:19.404 INFO 16588 --- [ Thread-5] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{2=MyContext} 2020-11-09 00:08:19.406 INFO 16588 --- [ Thread-6] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{3=MyContext} 2020-11-09 00:08:19.416 INFO 16588 --- [ Thread-7] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{4=MyContext} 2020-11-09 00:08:19.418 INFO 16588 --- [ Thread-8] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{5=MyContext} 2020-11-09 00:08:19.422 INFO 16588 --- [ Thread-9] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{6=MyContext} 2020-11-09 00:08:19.425 INFO 16588 --- [ Thread-10] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{7=MyContext} 2020-11-09 00:08:19.428 INFO 16588 --- [ Thread-11] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{8=MyContext} 2020-11-09 00:08:19.432 INFO 16588 --- [ Thread-12] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{9=MyContext} 2020-11-09 00:08:19.434 INFO 16588 --- [ Thread-13] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{10=MyContext} ``` 如果不加异步Agent，则输出结果，如下，可以发现在子线程中ThreadLocal上下文全部都丢失 ``` 2020-11-09 00:01:40.133 INFO 16692 --- [nio-8080-exec-1] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{1=MyContext} 2020-11-09 00:01:40.135 INFO 16692 --- [ Thread-8] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.158 INFO 16692 --- [nio-8080-exec-2] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{2=MyContext} 2020-11-09 00:01:40.159 INFO 16692 --- [ Thread-9] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.162 INFO 16692 --- [nio-8080-exec-3] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{3=MyContext} 2020-11-09 00:01:40.163 INFO 16692 --- [ Thread-10] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.170 INFO 16692 --- [nio-8080-exec-5] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{4=MyContext} 2020-11-09 00:01:40.170 INFO 16692 --- [ Thread-11] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.173 INFO 16692 --- [nio-8080-exec-4] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{5=MyContext} 2020-11-09 00:01:40.174 INFO 16692 --- [ Thread-12] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.176 INFO 16692 --- [nio-8080-exec-6] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{6=MyContext} 2020-11-09 00:01:40.177 INFO 16692 --- [ Thread-13] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.179 INFO 16692 --- [nio-8080-exec-8] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{7=MyContext} 2020-11-09 00:01:40.180 INFO 16692 --- [ Thread-14] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.182 INFO 16692 --- [nio-8080-exec-7] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{8=MyContext} 2020-11-09 00:01:40.182 INFO 16692 --- [ Thread-15] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.185 INFO 16692 --- [nio-8080-exec-9] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{9=MyContext} 2020-11-09 00:01:40.186 INFO 16692 --- [ Thread-16] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:40.188 INFO 16692 --- [io-8080-exec-10] c.n.d.example.application.MyApplication : 【主】线程ThreadLocal：{10=MyContext} 2020-11-09 00:01:40.189 INFO 16692 --- [ Thread-17] c.n.d.example.application.MyApplication : 【子】线程ThreadLocal：{} 2020-11-09 00:01:45.136 INFO 16692 --- [ Thread-8] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.160 INFO 16692 --- [ Thread-9] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.163 INFO 16692 --- [ Thread-10] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.171 INFO 16692 --- [ Thread-11] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.174 INFO 16692 --- [ Thread-12] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.177 INFO 16692 --- [ Thread-13] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.181 INFO 16692 --- [ Thread-14] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.183 INFO 16692 --- [ Thread-15] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.187 INFO 16692 --- [ Thread-16] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} 2020-11-09 00:01:45.190 INFO 16692 --- [ Thread-17] c.n.d.example.application.MyApplication : Sleep 5秒之后，【子】线程ThreadLocal：{} ``` 完整示例，请参考[https://github.com/Nepxion/DiscoveryAgent/tree/master/discovery-agent-example](https://github.com/Nepxion/DiscoveryAgent/tree/master/discovery-agent-example)。上述自定义插件的方式，即可解决使用者在线程切换时丢失ThreadLocal上下文的问题 ## 请联系我 微信、钉钉、公众号和文档 ![](http://nepxion.gitee.io/discovery/docs/zxing-doc/微信-1.jpg)![](http://nepxion.gitee.io/discovery/docs/zxing-doc/钉钉-1.jpg)![](http://nepxion.gitee.io/discovery/docs/zxing-doc/公众号-1.jpg)![](http://nepxion.gitee.io/discovery/docs/zxing-doc/文档-1.jpg) ## Star走势图 [![Stargazers over time](https://starchart.cc/Nepxion/Discovery.svg)](https://starchart.cc/Nepxion/Discovery)