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本篇文章给大家分享的是有关springcloud-sleuth源码怎么解析2-TraceFilter,小编觉得挺实用的,因此分享给大家学习,希望大家阅读完这篇文章后可以有所收获,话不多说,跟着小编一起来看看吧。
基于spring cloud 1.2.1版本
将分析server接收一个请求,trace究竟是怎么处理的。
首先介绍下一个span的生命周期:
start
创建一个span,这时候会记录创建时间以及设置span name。如果当前线程已经存在一个span,则创建的新的span是childSpan。
// Start a span. If there was a span present in this thread it will become // the `newSpan`'s parent. Span newSpan = this.tracer.createSpan("calculateTax"); try { // ... // You can tag a span this.tracer.addTag("taxValue", taxValue); // ... // You can log an event on a span newSpan.logEvent("taxCalculated"); } finally { // Once done remember to close the span. This will allow collecting // the span to send it to Zipkin this.tracer.close(newSpan); }
close
如果一个span已经准备好将自身发送到zipkin server或者其他collect的时候,便会调用close方法,记录endTime,上报span,然后从当前线程中移除span。
continue
将一个新的span设置到当前线程中,成为continueSpan。该方法作用是传递不同线程之间的span。对于一些异步处理代码,就需要 将span设置到异步处理线程中了。
Span continuedSpan = this.tracer.continueSpan(spanToContinue);
detach
从当前线程中删除span,剥离出去,但不会stop或者close span。一般跟continue方法结合使用。
// let's assume that we're in a thread Y and we've received // the `initialSpan` from thread X Span continuedSpan = this.tracer.continueSpan(initialSpan); try { // ... // You can tag a span this.tracer.addTag("taxValue", taxValue); // ... // You can log an event on a span continuedSpan.logEvent("taxCalculated"); } finally { // Once done remember to detach the span. That way you'll // safely remove it from the current thread without closing it this.tracer.detach(continuedSpan); }
create with explicit parent
创建一个span并且指定它的parent span。该方法的使用场景是在当前线程中想创建一个span,但parent span存在另一个线程当中,这样你 就可以获取到parent span,明确指定该span为要创建的span的parent。
// let's assume that we're in a thread Y and we've received // the `initialSpan` from thread X. `initialSpan` will be the parent // of the `newSpan` Span newSpan = this.tracer.createSpan("calculateCommission", initialSpan); try { // ... // You can tag a span this.tracer.addTag("commissionValue", commissionValue); // ... // You can log an event on a span newSpan.logEvent("commissionCalculated"); } finally { // Once done remember to close the span. This will allow collecting // the span to send it to Zipkin. The tags and events set on the // newSpan will not be present on the parent this.tracer.close(newSpan); }
下面介绍TraceFilter过滤器,它拦截所有请求,我们直接看它的doFilter方法。
@Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { if (!(servletRequest instanceof HttpServletRequest) || !(servletResponse instanceof HttpServletResponse)) { throw new ServletException("Filter just supports HTTP requests"); } HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; //首先从request获取到uri String uri = this.urlPathHelper.getPathWithinApplication(request); //判断是否忽略本次trace。根据两个条件判断是否忽略本次trace: //A、根据skipPattern判断此uri是否是skip uri,如果是返回true //B、从request、response的head中获取X-B3-Sampled属性,如果值为0则返回true,即不进行采样 boolean skip = this.skipPattern.matcher(uri).matches() || Span.SPAN_NOT_SAMPLED.equals(ServletUtils.getHeader(request, response, Span.SAMPLED_NAME)); //从request中getAttribute span。表示在一个request中,如果发生了转发那直接可以在request中获取span,不需要重新生成。 Span spanFromRequest = getSpanFromAttribute(request); if (spanFromRequest != null) { //不为空的话则continueSpan,下面看看continueSpan方法。 continueSpan(request, spanFromRequest); } if (log.isDebugEnabled()) { log.debug("Received a request to uri [" + uri + "] that should not be sampled [" + skip + "]"); } // in case of a response with exception status a exception controller will close the span //正如上面的注释所说,这是请求出现异常时,跳转到异常controller时处理逻辑,然后关闭span立即结束filter。 if (!httpStatusSuccessful(response) && isSpanContinued(request)) { Span parentSpan = parentSpan(spanFromRequest); processErrorRequest(filterChain, request, new TraceHttpServletResponse(response, parentSpan), spanFromRequest); return; } //设置span name String name = HTTP_COMPONENT + ":" + uri; Throwable exception = null; try { //根据request创建span,下面分析createSpan代码。 spanFromRequest = createSpan(request, skip, spanFromRequest, name); //这里会触发springmvc的trace拦截器TraceHandlerInterceptor的一些方法,下一章会分析。 filterChain.doFilter(request, new TraceHttpServletResponse(response, spanFromRequest)); } catch (Throwable e) { exception = e; this.tracer.addTag(Span.SPAN_ERROR_TAG_NAME, ExceptionUtils.getExceptionMessage(e)); throw e; } finally { //对于异步request则不进行处理 if (isAsyncStarted(request) || request.isAsyncStarted()) { if (log.isDebugEnabled()) { log.debug("The span " + spanFromRequest + " will get detached by a HandleInterceptor"); } // TODO: how to deal with response annotations and async? return; } //如果该请求没有被spring mvc的trace拦截器拦截到,则会人工的生成一个lc类型span,作为spanFromRequest的child span, //弥补springmvc的trace拦截器缺失的部分,这样能保证对于zipkin来说是一个合理的调用链路。 spanFromRequest = createSpanIfRequestNotHandled(request, spanFromRequest, name, skip); //分离获取关闭span,最后来分析下该方法 detachOrCloseSpans(request, response, spanFromRequest, exception); } }
private void continueSpan(HttpServletRequest request, Span spanFromRequest) { //tracer的continueSpan方法的作用是将新的span设置到当前线程中。 //比如span a 在线程X中,span b在线程Y中,现在上下文处于线程b中,然后操作continueSpan(a), //即将线程Y中的span b替换成span a,然后span a中的saved span属性设置成span b,即设置当前线程span之前的current span。 //下面分析下continueSpan方法。 this.tracer.continueSpan(spanFromRequest); request.setAttribute(TraceRequestAttributes.SPAN_CONTINUED_REQUEST_ATTR, "true"); if (log.isDebugEnabled()) { log.debug("There has already been a span in the request " + spanFromRequest); } }
public Span continueSpan(Span span) { if (span != null) { //日志组件,主要用于MDC输出的 this.spanLogger.logContinuedSpan(span); } else { return null; } //createContinuedSpan方法第一个参数span是request中保存的span,或者其他上下文传递下来的。 //第二个span,SpanContextHolder.getCurrentSpan()是从ThreadLocal获取当前线程中的span。 //下面看下createContinuedSpan方法 Span newSpan = createContinuedSpan(span, SpanContextHolder.getCurrentSpan()); //将新的span保存到当前线程中 SpanContextHolder.setCurrentSpan(newSpan); return newSpan; } //如果当前线程span为空且被传递过来的span的saved span属性不为空,则设置新的saved span为被传递过来的span的saved span, //否则saved span使用当前线程中的span。 private Span createContinuedSpan(Span span, Span saved) { if (saved == null && span.getSavedSpan() != null) { saved = span.getSavedSpan(); } return new Span(span, saved); }
对于new Span(span, saved)这种构造span的形式我们来分析下saved span有何作用:
saved的span是在创建该新的span之前就已经存在当前线程中的span。有两种情况会调用该api:
正如之前所说的,span从线程X复制到线程Y中
当前线程中已有span,然后创建child span,child span的saved span就是parent span
/** * Creates a span and appends it as the current request's attribute */ private Span createSpan(HttpServletRequest request, boolean skip, Span spanFromRequest, String name) { //如果spanFromRequest不为空,即发生了转发等情况,那直接返回,不需要创建新的span。 if (spanFromRequest != null) { if (log.isDebugEnabled()) { log.debug("Span has already been created - continuing with the previous one"); } return spanFromRequest; } //抽取request中的header、path等信息创建span,下面将分析joinTrace方法。 Span parent = this.spanExtractor.joinTrace(new HttpServletRequestTextMap(request)); //如果成功从request中提取了trace信息,生成了parent if (parent != null) { if (log.isDebugEnabled()) { log.debug("Found a parent span " + parent + " in the request"); } //正常tags中信息不会在server端添加,而是在client端添加tags。 //但是如果request header中不存在span name信息,说明client没有生成span信息,导致span信息不完整, //那么就需要在server端生成tags。 addRequestTagsForParentSpan(request, parent); spanFromRequest = parent; //将生成的span保存到当前线程中,详情看DefaultTracer.continueSpan方法,前面已分析。 this.tracer.continueSpan(spanFromRequest); //判断该span是否跨进程,是的话会加SR标识,即span生命周期中server recive阶段 if (parent.isRemote()) { parent.logEvent(Span.SERVER_RECV); } //将span保存到request中。 request.setAttribute(TRACE_REQUEST_ATTR, spanFromRequest); if (log.isDebugEnabled()) { log.debug("Parent span is " + parent + ""); } } else { //parent为空需要生成新的span //如果skip为true,则会生成一个不采样标识的span if (skip) { spanFromRequest = this.tracer.createSpan(name, NeverSampler.INSTANCE); } else { //根据request header中的采样标识判断直接采样,还是根据本地设置的采样器判断是否采样 //下面分析下DefaultTracer.createSpan方法 String header = request.getHeader(Span.SPAN_FLAGS); if (Span.SPAN_SAMPLED.equals(header)) { spanFromRequest = this.tracer.createSpan(name, new AlwaysSampler()); } else { spanFromRequest = this.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; }
public Span joinTrace(SpanTextMap textMap) { //carrier中保存request header、uri信息 Map<String, String> carrier = TextMapUtil.asMap(textMap); //判断header中是否有Span.SPAN_FLAGS标识,且值为1,即需要采样。 boolean debug = Span.SPAN_SAMPLED.equals(carrier.get(Span.SPAN_FLAGS)); if (debug) { // we're only generating Trace ID since if there's no Span ID will assume // that it's equal to Trace ID //header中如果不存在trace id,则生成一个。 generateIdIfMissing(carrier, Span.TRACE_ID_NAME); } else if (carrier.get(Span.TRACE_ID_NAME) == null) { // can't build a Span without trace id //header中没有trace id则直接返回null,不能从reqeust中提取信息构建span return null; } try { String uri = carrier.get(URI_HEADER); //根据uri判断是够skip boolean skip = this.skipPattern.matcher(uri).matches() || Span.SPAN_NOT_SAMPLED.equals(carrier.get(Span.SAMPLED_NAME)); //如果header中span id为空则根据trace id生成一个,否则直接返回header中的span id。 long spanId = spanId(carrier); //构建span return buildParentSpan(carrier, uri, skip, spanId); } catch (Exception e) { log.error("Exception occurred while trying to extract span from carrier", e); return null; } }
public Span createSpan(String name, Sampler sampler) { String shortenedName = SpanNameUtil.shorten(name); Span span; //如果本地即当前线程已经存在span,则创建child span,当前线程中的span为parent span //如果不存在span,则创建一个完全新的span if (isTracing()) { span = createChild(getCurrentSpan(), shortenedName); } else { long id = createId(); span = Span.builder().name(shortenedName) .traceIdHigh(this.traceId128 ? createId() : 0L) .traceId(id) .spanId(id).build(); if (sampler == null) { sampler = this.defaultSampler; } span = sampledSpan(span, sampler); this.spanLogger.logStartedSpan(null, span); } //将创建的span保存在当前线程 return continueSpan(span); }
private void detachOrCloseSpans(HttpServletRequest request, HttpServletResponse response, Span spanFromRequest, Throwable exception) { Span span = spanFromRequest; if (span != null) { //添加response status到tags中 addResponseTags(response, exception); //这里判断span中savedSpan不为空且请求被TraceHandlerInterceptor拦截器拦截处理过则上报savedSpan信息 //这里上报savedSpan,我的理解是traceFilter在filter一个request的时候会创建第一个parentSpan, //期间不会创建childSpan,但进入springmvc handler处理期间可能会创建一些childSpan,然后设置为current span, //但这种span不是traceFilter关注的,它只关注server reciver时即刚接收到请求创建的span。 if (span.hasSavedSpan() && requestHasAlreadyBeenHandled(request)) { //首先停止span的clock,即记录结束时间,算下开始时间与结束时间的duration。 //然后记录server send event,表明作为server端,什么时候响应请求返回结果的。 //最后上报span,比如上报到zipkin或者打印log,这就取决于初始化哪种spanReporter的了。 recordParentSpan(span.getSavedSpan()); } else if (!requestHasAlreadyBeenHandled(request)) { //如果该请求没有被TraceHandlerInterceptor拦截器拦截处理,则直接把span从当前线程中移除,停止span的clock,然后上报 //这里的span可能是createSpanIfRequestNotHandled创建的span。 //close返回savedSpan,即parentSpan span = this.tracer.close(span); } //上报parentSpan recordParentSpan(span); // in case of a response with exception status will close the span when exception dispatch is handled // checking if tracing is in progress due to async / different order of view controller processing if (httpStatusSuccessful(response) && this.tracer.isTracing()) { if (log.isDebugEnabled()) { log.debug("Closing the span " + span + " since the response was successful"); } this.tracer.close(span); } else if (errorAlreadyHandled(request) && this.tracer.isTracing()) { if (log.isDebugEnabled()) { log.debug( "Won't detach the span " + span + " since error has already been handled"); } } else if (shouldCloseSpan(request) && this.tracer.isTracing() && stillTracingCurrentSapn(span)) { if (log.isDebugEnabled()) { log.debug( "Will close span " + span + " since some component marked it for closure"); } this.tracer.close(span); } else if (this.tracer.isTracing()) { if (log.isDebugEnabled()) { log.debug("Detaching the span " + span + " since the response was unsuccessful"); } this.tracer.detach(span); } } }
以上就是springcloud-sleuth源码怎么解析2-TraceFilter,小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注亿速云行业资讯频道。
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