skywalking07 - skywalking如何收集Controller的链路
对于我们在java中常用的注解@Controller、@RestController，在运行时，将会产生链路，在“链路追踪”中可以进行查看，那么来看看怎么收集的
Instrumentation 指明拦截的类
- 在
org.apache.skywalking.apm.plugin.spring.mvc.v5.define.AbstractControllerInstrumentation抽象类的实现类ControllerInstrumentation、RestControllerInstrumentation中指定了ENHANCE_ANNOTATION分别为org.springframework.stereotype.Controller以及org.springframework.web.bind.annotation.RestController进行指定了增强的类。
public class RestControllerInstrumentation extends AbstractControllerInstrumentation {
public static final String ENHANCE_ANNOTATION = "org.springframework.web.bind.annotation.RestController";
@Override
protected String[] getEnhanceAnnotations() {
return new String[] {ENHANCE_ANNOTATION};
}
}- 然后通过如下方法指定拦截增强的方法
@Override
public InstanceMethodsInterceptPoint[] getInstanceMethodsInterceptPoints() {
return new InstanceMethodsInterceptPoint[] {
new DeclaredInstanceMethodsInterceptPoint() {
@Override
public ElementMatcher<MethodDescription> getMethodsMatcher() {
return byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.RequestMapping"));
}
},
new DeclaredInstanceMethodsInterceptPoint() {
@Override
public ElementMatcher<MethodDescription> getMethodsMatcher() {
return byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.GetMapping"))
.or(byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.PostMapping")))
.or(byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.PutMapping")))
.or(byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.DeleteMapping")))
.or(byMethodInheritanceAnnotationMatcher(named("org.springframework.web.bind.annotation.PatchMapping")));
}
}
};
}- 同时定义了用来增强该类的增强类
org.apache.skywalking.apm.plugin.spring.mvc.v5.ControllerConstructorInterceptor
InstanceConstructorInterceptor 进行类的增强
拦截构造实例的增强，直接对该Controller进行增强。该段代码中的注释比较重要！
/**
* The <code>ControllerConstructorInterceptor</code> intercepts the Controller's constructor, in order to acquire the
* mapping annotation, if exist.
* <p>
* But, you can see we only use the first mapping value, <B>Why?</B>
* <p>
* Right now, we intercept the controller by annotation as you known, so we CAN'T know which uri patten is actually
* matched. Even we know, that costs a lot.
* <p>
* If we want to resolve that, we must intercept the Spring MVC core codes, that is not a good choice for now.
* <p>
* Comment by @wu-sheng
*/
public class ControllerConstructorInterceptor implements InstanceConstructorInterceptor {
@Override
public void onConstruct(EnhancedInstance objInst, Object[] allArguments) {
String basePath = "";
RequestMapping basePathRequestMapping = objInst.getClass().getAnnotation(RequestMapping.class);
if (basePathRequestMapping != null) {
if (basePathRequestMapping.value().length > 0) {
basePath = basePathRequestMapping.value()[0];
} else if (basePathRequestMapping.path().length > 0) {
basePath = basePathRequestMapping.path()[0];
}
}
EnhanceRequireObjectCache enhanceRequireObjectCache = new EnhanceRequireObjectCache();
// PathMappingCache对象会存储方法中方法与URL映射的映射关系
enhanceRequireObjectCache.setPathMappingCache(new PathMappingCache(basePath));
objInst.setSkyWalkingDynamicField(enhanceRequireObjectCache);
}
}- Right now, we intercept the controller by annotation as you known, so we CAN’T know which uri patten is actually matched. Even we know, that costs a lot.
截止目前，我们用注解的方式拦截controller，所以我们不知道匹配的具体的URI。即使我们能够知道，但是那个消耗太大。 - If we want to resolve that, we must intercept the Spring MVC core codes, that is not a good choice for now.
如果我们想要去解决这个问题，我们必须拦截Spring MVC 核心代码，但是目前那不是个好选择。
这段话，说明了一个问题，如果有如下代码：
@GetMapping("/test/{pageId}")
public ApiResult<Boolean> test(@PathVariable("pageId") String pageId) {
return ApiResult.ok(true);
}那么在链路追踪中，看到的链路就是：{GET} XXX/test/{pageId}，那么这个pageId并不会使用实际的值，例如“00001”等等，这么做主要考虑了性能的消耗。
不过这么做，对于进行性能分析会带来一定的困扰。尤其是我们工程中，每一个页面都是特殊编辑生成的，每个页面的性能相差巨大，如果仅仅是这样的展示，我们运用链路追踪中的Duration进行排序，则不会按照pageId进行归类了，很是头疼。所以你有解决方案吗？
AbstractMethodInterceptor 进行方法的增强
org.apache.skywalking.apm.plugin.spring.mvc.commons.interceptor.AbstractMethodInterceptor是RequestMappingMethodInterceptor以及RestMappingMethodInterceptor的父类。对方法进行增强，将上一步的映射关系在EnhanceRequireObjectCache中真正形成。并且生成对应的EntrySpan或者LocalSpan。
@Override
public void beforeMethod(EnhancedInstance objInst, Method method, Object[] allArguments, Class<?>[] argumentsTypes,
MethodInterceptResult result) throws Throwable {
Boolean forwardRequestFlag = (Boolean) ContextManager.getRuntimeContext().get(FORWARD_REQUEST_FLAG);
/**
* Spring MVC plugin do nothing if current request is forward request.
* Ref: https://github.com/apache/skywalking/pull/1325
*/
if (forwardRequestFlag != null && forwardRequestFlag) {
return;
}
String operationName;
if (SpringMVCPluginConfig.Plugin.SpringMVC.USE_QUALIFIED_NAME_AS_ENDPOINT_NAME) {
operationName = MethodUtil.generateOperationName(method);
} else {
EnhanceRequireObjectCache pathMappingCache = (EnhanceRequireObjectCache) objInst.getSkyWalkingDynamicField();
String requestURL = pathMappingCache.findPathMapping(method);
if (requestURL == null) {
requestURL = getRequestURL(method);
// 添加方法与URL的映射关系
pathMappingCache.addPathMapping(method, requestURL);
requestURL = pathMappingCache.findPathMapping(method);
}
operationName = getAcceptedMethodTypes(method) + requestURL;
}
RequestHolder request = (RequestHolder) ContextManager.getRuntimeContext()
.get(REQUEST_KEY_IN_RUNTIME_CONTEXT);
if (request != null) {
StackDepth stackDepth = (StackDepth) ContextManager.getRuntimeContext().get(CONTROLLER_METHOD_STACK_DEPTH);
if (stackDepth == null) {
// 栈为空，为一个新的链路
ContextCarrier contextCarrier = new ContextCarrier();
CarrierItem next = contextCarrier.items();
while (next.hasNext()) {
next = next.next();
next.setHeadValue(request.getHeader(next.getHeadKey()));
}
// 创建一个EntrySpan
AbstractSpan span = ContextManager.createEntrySpan(operationName, contextCarrier);
Tags.URL.set(span, request.requestURL());
Tags.HTTP.METHOD.set(span, request.requestMethod());
span.setComponent(ComponentsDefine.SPRING_MVC_ANNOTATION);
SpanLayer.asHttp(span);
if (SpringMVCPluginConfig.Plugin.SpringMVC.COLLECT_HTTP_PARAMS) {
collectHttpParam(request, span);
}
if (!CollectionUtil.isEmpty(SpringMVCPluginConfig.Plugin.Http.INCLUDE_HTTP_HEADERS)) {
collectHttpHeaders(request, span);
}
stackDepth = new StackDepth();
// 加入一个栈深度
ContextManager.getRuntimeContext().put(CONTROLLER_METHOD_STACK_DEPTH, stackDepth);
} else {
// 本地调用，创建一个LocalSpan
AbstractSpan span = ContextManager.createLocalSpan(buildOperationName(objInst, method));
span.setComponent(ComponentsDefine.SPRING_MVC_ANNOTATION);
}
stackDepth.increment();
}
}总结
Controller的链路收集，主要分两步，一步是对类的增强，一步是对方法的增强。代码均位于apm-sniffer/apm-sdk-plugin/spring-plugins子工程中。
skywalking收集链路时，使用的URL都是通配符，在链路中，无法针对某个pageId，或者其他通配符的具体的值进行查找。或许skywalking出于性能考虑，但是对于这种不定的通用大接口，的确无法用于针对性的性能分析了。这个问题还需要深入思考寻找，能否在自己项目中，找到一个Balance，只针对自己需要分析性能的接口，按照具体值进行收集，而其他走默认呢？
PS:补充一下版本，SW 8.4版本，新版中已经将agent的部分抽到另一个git中了。
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