什么是spring-cloud-sleuth+zipkin源码

今天就跟大家聊聊有关什么是spring-cloud-sleuth+zipkin源码，可能很多人都不太了解，为了让大家更加了解，小编给大家总结了以下内容，希望大家根据这篇文章可以有所收获。

1.1. 前言

  粗略看了下spring cloud sleuth core源码，发现内容真的有点多，它支持了很多类型的链路追踪，我就找其中一个比较有代表性的深入剖析下源码结构和内容

1.2. spring-cloud-sleuth-core源码解析

1.2.1. 结构

1. 可以看到源码中支持的追踪类型有很多，支持async，hystrix，websocket，rxjava，Spring mvc，servlet，spring restTemplate，feign，zuul等等，这里我着重探讨spring web mvc的链路追踪

2. 打开web包，找到TraceWebAutoConfiguration，这里配置了主要的初始化类
   

1.2.2. 过滤器注册

1. 当启动初始化程序时，跟踪代码如下

    @Bean    public FilterRegistrationBean traceWebFilter(TraceFilter traceFilter) {        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(                traceFilter);        filterRegistrationBean.setDispatcherTypes(ASYNC, ERROR, FORWARD, INCLUDE,                REQUEST);        filterRegistrationBean.setOrder(TraceFilter.ORDER);        return filterRegistrationBean;    }    @Bean    @ConditionalOnMissingBean    public TraceFilter traceFilter(BeanFactory beanFactory,            SkipPatternProvider skipPatternProvider) {        return new TraceFilter(beanFactory, skipPatternProvider.skipPattern());    }

1. 初始化traceFilter，进行过滤器注册

1.2.3. 拦截器注册

1. 然后看TraceWebMvcConfigurer类，它会进行拦截器的注册

@Configurationclass TraceWebMvcConfigurer extends WebMvcConfigurerAdapter {    @Autowired BeanFactory beanFactory;    @Bean    public TraceHandlerInterceptor traceHandlerInterceptor(BeanFactory beanFactory) {        return new TraceHandlerInterceptor(beanFactory);    }    @Override    public void addInterceptors(InterceptorRegistry registry) {        registry.addInterceptor(this.beanFactory.getBean(TraceHandlerInterceptor.class));    }}

1. 在TraceHandlerInterceptor类中，preHandle,afterCompletion方法可以看出，这是对请求进行拦截进行span的包装

    @Override    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,            Object handler) throws Exception {        String spanName = spanName(handler);        boolean continueSpan = getRootSpanFromAttribute(request) != null;        Span span = continueSpan ? getRootSpanFromAttribute(request) : getTracer().createSpan(spanName);        if (log.isDebugEnabled()) {            log.debug("Handling span ">

    @Override    public void afterCompletion(HttpServletRequest request, HttpServletResponse response,            Object handler, Exception ex) throws Exception {        if (isErrorControllerRelated(request)) {            if (log.isDebugEnabled()) {                log.debug("Skipping closing of a span for error controller processing");            }            return;        }        Span span = getRootSpanFromAttribute(request);        if (ex != null) {            getErrorParser().parseErrorTags(span, ex);        }        if (getNewSpanFromAttribute(request) != null) {            if (log.isDebugEnabled()) {                log.debug("Closing span " + span);            }            Span newSpan = getNewSpanFromAttribute(request);            getTracer().continueSpan(newSpan);            getTracer().close(newSpan);            clearNewSpanCreatedAttribute(request);        }    }

1.2.4. zipkin端点提交

1. 这里首先会初始化HttpZipkinSpanReporter类，，用来进行span端点提交，然后初始化ZipkinSpanListenerspan的监听器，用来监听并调用端点提交，以上配置再下图位置
   

1.2.5. 调用http接口时，进入过滤器

1. 首先进入TraceFilter中的过滤方法doFilter，这里会做span的创建

private Span createSpan(HttpServletRequest request,            boolean skip, Span spanFromRequest, String name) {        if (spanFromRequest != null) {            if (log.isDebugEnabled()) {                log.debug("Span has already been created - continuing with the previous one");            }            return spanFromRequest;        }        //加入调用链路ZipkinHttpSpanExtractor，此链路在TraceHttpAutoConfiguration中配置实例化，调用链还没有时，返回为空，作为头节点        Span parent = spanExtractor().joinTrace(new HttpServletRequestTextMap(request));        if (parent != null) {            if (log.isDebugEnabled()) {                log.debug("Found a parent span ">

1.2.6. 进入拦截器

1. 在preHandle方法中，对span进行包装，然后把span放入请求头header中

2. 最后再DefaultTracer中进行span的关闭和spanReporter的提交

看完上述内容，你们对什么是spring-cloud-sleuth+zipkin源码有进一步的了解吗？如果还想了解更多知识或者相关内容，请关注行业资讯频道，感谢大家的支持。