spring-cloud Sleuth的使用方法
这篇文章主要介绍了spring-cloud Sleuth的使用方法，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧一直没弄明白sleuth的tracercontext是如何创建和传递的，闲来无事研究了一下。由于对sleuth的源码不熟悉，准备通过debug brave.tracer的nextid()方法，查看方法调用栈来找来龙去脉。
首先创建两个service a和b，记作srva、srvb，在srva中添加testa controller，sevb中添加testb controller，testa中通过feign调用testb。
先看当用户通过浏览器调用srva的时候，srva是作为server的。
configuration:
tracewebservletautoconfiguration==>tracingfilter
tracehttpautoconfiguration==>httptracing
traceautoconfiguration==>tracing
sleuthlogautoconfiguration.slf4jconfiguration==>currenttracecontext
配置中，tracingfilter在实例化时需要一个httptracing：
public static filter create(httptracing httptracing) {
return new tracingfilter(httptracing);
}
//servlet运行时类
final servletruntime servlet = servletruntime.get();
//slf4jcurrenttracecontext
final currenttracecontext currenttracecontext;
final tracer tracer;
final httpserverhandler<httpservletrequest, httpservletresponse> handler;
//tracecontext的数据提取器
final tracecontext.extractor<httpservletrequest> extractor;
tracingfilter(httptracing httptracing) {
tracer = httptracing.tracing().tracer();
currenttracecontext = httptracing.tracing().currenttracecontext();
handler = httpserverhandler.create(httptracing, adapter);
extractor = httptracing.tracing().propagation().extractor(getter);
}
httptracing builder模式构造时接收一个tracing：
tracing tracing;
//客户端span解析器
httpclientparser clientparser;
string servername;
//服务端span解析器
httpserverparser serverparser;
httpsampler clientsampler, serversampler;
builder(tracing tracing) {
if (tracing == null) throw new nullpointerexception("tracing == null");
final errorparser errorparser = tracing.errorparser();
this.tracing = tracing;
this.servername = "";
// override to re-use any custom error parser from the tracing component
this.clientparser = new httpclientparser() {
@override protected errorparser errorparser() {
return errorparser;
}
};
this.serverparser = new httpserverparser() {
@override protected errorparser errorparser() {
return errorparser;
}
};
this.clientsampler = httpsampler.trace_id;
this.serversampler(httpsampler.trace_id);
}
tracing实例化：
@bean
@conditionalonmissingbean
// note: stable bean name as might be used outside sleuth
tracing tracing(@value("${spring.zipkin.service.name:${spring.application.name:default}}") string servicename,
propagation.factory factory,
currenttracecontext currenttracecontext,
reporter<zipkin2.span> reporter,
sampler sampler,
errorparser errorparser,
sleuthproperties sleuthproperties
) {
return tracing.newbuilder()
.sampler(sampler)
.errorparser(errorparser)
.localservicename(servicename)
//extrafieldpropagation.factory
.propagationfactory(factory)
.currenttracecontext(currenttracecontext)
.spanreporter(adjustedreporter(reporter))
.traceid128bit(sleuthproperties.istraceid128())
.supportsjoin(sleuthproperties.issupportsjoin())
.build();
}
下面看tracingfilter的dofilter：
span span = handler.handlereceive(extractor, httprequest);
// add attributes for explicit access to customization or span context
request.setattribute(spancustomizer.class.getname(), span.customizer());
request.setattribute(tracecontext.class.getname(), span.context());
throwable error = null;
scope scope = currenttracecontext.newscope(span.context());
try {
// any downstream code can see tracer.currentspan() or use tracer.currentspancustomizer()
chain.dofilter(httprequest, httpresponse);
} catch (ioexception | servletexception | runtimeexception | error e) {
error = e;
throw e;
} finally {
scope.close();
if (servlet.isasync(httprequest)) { // we don't have the actual response, handle later
servlet.handleasync(handler, httprequest, httpresponse, span);
} else { // we have a synchronous response, so we can finish the span
handler.handlesend(adapter.adaptresponse(httprequest, httpresponse), error, span);
}
}
}
在sleuthlogautoconfiguration中如果有slfj的包，则注入currenttracecontext：
@configuration
@conditionalonclass(mdc.class)
@enableconfigurationproperties(sleuthslf4jproperties.class)
protected static class slf4jconfiguration {
@bean
@conditionalonproperty(value = "spring.sleuth.log.slf4j.enabled", matchifmissing = true)
@conditionalonmissingbean
public currenttracecontext slf4jspanlogger() {
return slf4jcurrenttracecontext.create();
}
...
}
slf4jcurrenttracecontext中，delegate就是currenttracecontext.default.inheritable()：
public static final class default extends currenttracecontext {
static final threadlocal<tracecontext> default = new threadlocal<>();
// inheritable as brave 3's threadlocalserverclientandlocalspanstate was inheritable
static final inheritablethreadlocal<tracecontext> inheritable = new inheritablethreadlocal<>();
final threadlocal<tracecontext> local;
//静态方法create，local对象为threadlocal类型
/** uses a non-inheritable static thread local */
public static currenttracecontext create() {
return new default(default);
}
//local对象为inheritablethreadlocal类型
//官方文档指出，inheritable方法在线程池的环境中需谨慎使用，可能会取出错误的tracecontext，这样会导致span等信息会记录并关联到错误的traceid上
/**
* uses an inheritable static thread local which allows arbitrary calls to {@link
* thread#start()} to automatically inherit this context. this feature is available as it is was
* the default in brave 3, because some users couldn't control threads in their applications.
*
* <p>this can be a problem in scenarios such as thread pool expansion, leading to data being
* recorded in the wrong span, or spans with the wrong parent. if you are impacted by this,
* switch to {@link #create()}.
*/
public static currenttracecontext inheritable() {
return new default(inheritable);
}
default(threadlocal<tracecontext> local) {
if (local == null) throw new nullpointerexception("local == null");
this.local = local;
}
@override public tracecontext get() {
return local.get();
}
//替换当前tracecontext，close方法将之前的tracecontext设置回去
//scope接口继承了closeable接口，在try中使用会自动调用close方法，为了避免用户忘记close方法，还提供了runnable，callable，executor，executorservice包装方法
@override public scope newscope(@nullable tracecontext currentspan) {
final tracecontext previous = local.get();
local.set(currentspan);
class defaultcurrenttracecontextscope implements scope {
@override public void close() {
local.set(previous);
}
}
return new defaultcurrenttracecontextscope();
}
}
slf4jcurrenttracecontext的delegate使用的就是一个inheritablethreadlocal，inheritablethreadlocal在创建子线程的时候，会将父线程的inheritablethreadlocals继承下来。这样就实现了tracecontext在父子线程中的传递。
看一下currenttracecontext的maybescope：
//返回一个新的scope，如果当前scope就是传入的scope，返回一个空scope
public scope maybescope(@nullable tracecontext currentspan) {
//获取当前tracecontext
tracecontext currentscope = get();
//如果传入的tracecontext为空，且当前tracecontext为空返回空scope
if (currentspan == null) {
if (currentscope == null) return scope.noop;
return newscope(null);
}
return currentspan.equals(currentscope) ? scope.noop : newscope(currentspan);
}
tracingfilter中httpserverhandler解析request：请输入代码
2.srva请求到servb时作为client。
traceloadbalancerfeignclient-->loadbalancerfeignclient-->feignloadbalancer-->lazytracingfeignclient-->client
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持CodeAE代码之家。
原文链接：https://segmentfault.com/a/1190000018115247
http://www.zzvips.com/article/176524.html
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