spring-cloud-sleuth+zipkin原始碼探究
阿新 • • 發佈：2019-09-09
1.1. 前言
粗略看了下spring cloud sleuth core原始碼，發現內容真的有點多，它支援了很多型別的鏈路追蹤，我就找其中一個比較有代表性的深入剖析下原始碼結構和內容
1.2. spring-cloud-sleuth-core原始碼解析
1.2.1. 結構
- 可以看到原始碼中支援的追蹤型別有很多，支援async，hystrix，websocket，rxjava，Spring mvc，servlet，spring restTemplate，feign，zuul等等，這裡我著重探討spring web mvc的鏈路追蹤
- 開啟web包，找到TraceWebAutoConfiguration，這裡配置了主要的初始化類
1.2.2. 過濾器註冊
- 當啟動初始化程式時，跟蹤程式碼如下
@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()); }
- 初始化traceFilter，進行過濾器註冊
1.2.3. 攔截器註冊
- 然後看
TraceWebMvcConfigurer類，它會進行攔截器的註冊
@Configuration class 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)); } }
- 在
TraceHandlerInterceptor類中，preHandle,afterCompletion方法可以看出，這是對請求進行攔截進行span的包裝
@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 " + span);
}
addClassMethodTag(handler, span);
addClassNameTag(handler, span);
setSpanInAttribute(request, span);
if (!continueSpan) {
setNewSpanCreatedAttribute(request, span);
}
return true;
} @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端點提交
- 這裡首先會初始化
HttpZipkinSpanReporter類，，用來進行span端點提交，然後初始化ZipkinSpanListenerspan的監聽器，用來監聽並呼叫端點提交，以上配置再下圖位置
1.2.5. 呼叫http介面時，進入過濾器
- 首先進入
TraceFilter中的過濾方法doFilter，這裡會做span的建立
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;
}
//加入呼叫鏈路ZipkinHttpSpanExtractor，此鏈路在TraceHttpAutoConfiguration中配置例項化，呼叫鏈還沒有時，返回為空，作為頭節點
Span parent = spanExtractor().joinTrace(new HttpServletRequestTextMap(request));
if (parent != null) {
if (log.isDebugEnabled()) {
log.debug("Found a parent span " + parent + " in the request");
}
addRequestTagsForParentSpan(request, parent);
spanFromRequest = parent;
tracer().continueSpan(spanFromRequest);
if (parent.isRemote()) {
parent.logEvent(Span.SERVER_RECV);
}
request.setAttribute(TRACE_REQUEST_ATTR, spanFromRequest);
if (log.isDebugEnabled()) {
log.debug("Parent span is " + parent + "");
}
} else {
if (skip) {
spanFromRequest = tracer().createSpan(name, NeverSampler.INSTANCE);
}
else {
String header = request.getHeader(Span.SPAN_FLAGS);
if (Span.SPAN_SAMPLED.equals(header)) {
spanFromRequest = tracer().createSpan(name, new AlwaysSampler());
} else {
//建立span節點
spanFromRequest = tracer().createSpan(name);
}
}
spanFromRequest.logEvent(Span.SERVER_RECV);
request.setAttribute(TRACE_REQUEST_ATTR, spanFromRequest);
if (log.isDebugEnabled()) {
log.debug("No parent span present - creating a new span");
}
}
return spanFromRequest;
}1.2.6. 進入攔截器
- 在
preHandle方法中，對span進行包裝，然後把span放入請求頭header中 - 最後再
DefaultTracer中進行span的關閉和spanReporter