跟着controller走到了enhance

qisiii · qisiii · commit 2fae67b6871c · 2023-08-23T00:04:36.000+08:00
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/AbstractClassEnhancePluginDefine.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/AbstractClassEnhancePluginDefine.java
@@ -68,6 +68,7 @@ public DynamicType.Builder<?> define(TypeDescription typeDescription, DynamicTyp
 
         LOGGER.debug("prepare to enhance class {} by {}.", transformClassName, interceptorDefineClassName);
         WitnessFinder finder = WitnessFinder.INSTANCE;
+        //witness感觉更像是在加载某类之前，必须有些类已经加载
         /**
          * find witness classes for enhance class
          */
@@ -110,6 +111,7 @@ public DynamicType.Builder<?> define(TypeDescription typeDescription, DynamicTyp
      */
     protected DynamicType.Builder<?> enhance(TypeDescription typeDescription, DynamicType.Builder<?> newClassBuilder,
                                              ClassLoader classLoader, EnhanceContext context) throws PluginException {
+        //这里是实际和插件作用的地方
         newClassBuilder = this.enhanceClass(typeDescription, newClassBuilder, classLoader);
 
         newClassBuilder = this.enhanceInstance(typeDescription, newClassBuilder, classLoader, context);
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginBootstrap.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginBootstrap.java
@@ -54,26 +54,30 @@ public List<AbstractClassEnhancePluginDefine> loadPlugins() throws AgentPackageN
 
         for (URL pluginUrl : resources) {
             try {
+                //最终都加载到了List<PluginDefine> pluginClassList里
                 PluginCfg.INSTANCE.load(pluginUrl.openStream());
             } catch (Throwable t) {
                 LOGGER.error(t, "plugin file [{}] init failure.", pluginUrl);
             }
         }
 
         List<PluginDefine> pluginClassList = PluginCfg.INSTANCE.getPluginClassList();
-
+        //从这里往下的暂时没有看懂
         List<AbstractClassEnhancePluginDefine> plugins = new ArrayList<AbstractClassEnhancePluginDefine>();
         for (PluginDefine pluginDefine : pluginClassList) {
             try {
                 LOGGER.debug("loading plugin class {}.", pluginDefine.getDefineClass());
+                //Q&A 2023/8/22
+                // Q:为什么这里所有的类都能强转为AbstractClassEnhancePluginDefine
+                // A:因为插件继承的顶层最终都是这个抽象类
                 AbstractClassEnhancePluginDefine plugin = (AbstractClassEnhancePluginDefine) Class.forName(pluginDefine.getDefineClass(), true, AgentClassLoader
                     .getDefault()).newInstance();
                 plugins.add(plugin);
             } catch (Throwable t) {
                 LOGGER.error(t, "load plugin [{}] failure.", pluginDefine.getDefineClass());
             }
         }
-
+        //这个是通过SPI用所有的InstrumentationLoader来添加AbstractClassEnhancePluginDefine，不知道用在哪
         plugins.addAll(DynamicPluginLoader.INSTANCE.load(AgentClassLoader.getDefault()));
 
         return plugins;
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginCfg.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginCfg.java
@@ -46,6 +46,11 @@ void load(InputStream input) throws IOException {
                     if (pluginDefine.trim().length() == 0 || pluginDefine.startsWith("#")) {
                         continue;
                     }
+                    //e.g.
+                    //spring-mvc-annotation-3.x=org.apache.skywalking.apm.plugin.spring.mvc.v3.define.ControllerInstrumentation
+                    //spring-mvc-annotation-3.x=org.apache.skywalking.apm.plugin.spring.mvc.v3.define.HandlerMethodInstrumentation
+                    //spring-mvc-annotation-3.x=org.apache.skywalking.apm.plugin.spring.mvc.v3.define.InvocableHandlerInstrumentation
+                    //spring-mvc-annotation-3.x=org.apache.skywalking.apm.plugin.spring.mvc.v3.define.HandlerMethodInvokerInstrumentation
                     PluginDefine plugin = PluginDefine.build(pluginDefine);
                     pluginClassList.add(plugin);
                 } catch (IllegalPluginDefineException e) {
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginFinder.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/PluginFinder.java
@@ -52,7 +52,7 @@ public PluginFinder(List<AbstractClassEnhancePluginDefine> plugins) {
             if (match == null) {
                 continue;
             }
-
+            //重写enhanceClass，以restTemplate为例，NameMatch.byName("org.springframework.web.client.RestTemplate")
             if (match instanceof NameMatch) {
                 NameMatch nameMatch = (NameMatch) match;
                 LinkedList<AbstractClassEnhancePluginDefine> pluginDefines = nameMatchDefine.get(nameMatch.getClassName());
@@ -88,6 +88,10 @@ public List<AbstractClassEnhancePluginDefine> find(TypeDescription typeDescripti
         return matchedPlugins;
     }
 
+    /**
+     * 主要是通过插件里定义的NameMatch和IndirectMatch来匹配，IndirectMatch就是要更复杂，比如匹配的更多，前缀，后缀之类的，参考IndirectMatch的实现类
+     * @return
+     */
     public ElementMatcher<? super TypeDescription> buildMatch() {
         ElementMatcher.Junction judge = new AbstractJunction<NamedElement>() {
             @Override
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/bootstrap/BootstrapInstrumentBoost.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/bootstrap/BootstrapInstrumentBoost.java
@@ -87,7 +87,7 @@ public class BootstrapInstrumentBoost {
     public static AgentBuilder inject(PluginFinder pluginFinder, Instrumentation instrumentation,
         AgentBuilder agentBuilder, JDK9ModuleExporter.EdgeClasses edgeClasses) throws PluginException {
         Map<String, byte[]> classesTypeMap = new LinkedHashMap<>();
-
+        //这两个方法都似乎是在处理bootstrap相关的类
         if (!prepareJREInstrumentation(pluginFinder, classesTypeMap)) {
             return agentBuilder;
         }
@@ -116,6 +116,7 @@ public static AgentBuilder inject(PluginFinder pluginFinder, Instrumentation ins
          */
         ClassInjector.UsingUnsafe.Factory factory = ClassInjector.UsingUnsafe.Factory.resolve(instrumentation);
         factory.make(null, null).injectRaw(classesTypeMap);
+        //实际在这个地方注入了所有需要注入到引导类加载器对应的类
         agentBuilder = agentBuilder.with(new AgentBuilder.InjectionStrategy.UsingUnsafe.OfFactory(factory));
 
         return agentBuilder;
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/loader/AgentClassLoader.java b/apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/plugin/loader/AgentClassLoader.java
@@ -86,7 +86,7 @@ public AgentClassLoader(ClassLoader parent) throws AgentPackageNotFoundException
         super(parent);
         File agentDictionary = AgentPackagePath.getPath();
         classpath = new LinkedList<>();
-        //将jar包加到类路径
+        //将jar包加到类路径；MOUNT（"plugins", "activations"）
         Config.Plugin.MOUNT.forEach(mountFolder -> classpath.add(new File(agentDictionary, mountFolder)));
     }
 
diff --git a/apm-sniffer/apm-agent/src/main/java/org/apache/skywalking/apm/agent/SkyWalkingAgent.java b/apm-sniffer/apm-agent/src/main/java/org/apache/skywalking/apm/agent/SkyWalkingAgent.java
@@ -65,6 +65,7 @@ public class SkyWalkingAgent {
     public static void premain(String agentArgs, Instrumentation instrumentation) throws PluginException {
         final PluginFinder pluginFinder;
         try {
+            //将各个途径的配置都处理汇总到CONFIG类里，里面全是静态字段，所以直接赋值也不需要实例化对象
             SnifferConfigInitializer.initializeCoreConfig(agentArgs);
         } catch (Exception e) {
             // try to resolve a new logger, and use the new logger to write the error log here
@@ -82,6 +83,7 @@ public static void premain(String agentArgs, Instrumentation instrumentation) th
         }
 
         try {
+            //这一步实际上是加载了插件jar包里的增加类def里面描述的类，最终都传到了PluginFinder，存储为三种不同的对象
             pluginFinder = new PluginFinder(new PluginBootstrap().loadPlugins());
         } catch (AgentPackageNotFoundException ape) {
             LOGGER.error(ape, "Locate agent.jar failure. Shutting down.");
@@ -92,7 +94,7 @@ public static void premain(String agentArgs, Instrumentation instrumentation) th
         }
         //byte-buddy是一个字节码生成和操作库
         final ByteBuddy byteBuddy = new ByteBuddy().with(TypeValidation.of(Config.Agent.IS_OPEN_DEBUGGING_CLASS));
-
+        //bytebuddy提供的更便捷的工具
         AgentBuilder agentBuilder = new AgentBuilder.Default(byteBuddy).ignore(
             nameStartsWith("net.bytebuddy.")
                 .or(nameStartsWith("org.slf4j."))
@@ -103,7 +105,9 @@ public static void premain(String agentArgs, Instrumentation instrumentation) th
                 .or(nameStartsWith("sun.reflect"))
                 .or(allSkyWalkingAgentExcludeToolkit())
                 .or(ElementMatchers.isSynthetic()));
-
+        //Q&A 2023/8/14
+        // Q: 这里好像是jdk9开始引入的模块化的概念，需要了解学习
+        // A:
         JDK9ModuleExporter.EdgeClasses edgeClasses = new JDK9ModuleExporter.EdgeClasses();
         try {
             agentBuilder = BootstrapInstrumentBoost.inject(pluginFinder, instrumentation, agentBuilder, edgeClasses);
@@ -113,6 +117,9 @@ public static void premain(String agentArgs, Instrumentation instrumentation) th
         }
 
         try {
+            //Q&A 2023/8/14
+            // Q: 先不看，毕竟不懂模块
+            // A:
             agentBuilder = JDK9ModuleExporter.openReadEdge(instrumentation, agentBuilder, edgeClasses);
         } catch (Exception e) {
             LOGGER.error(e, "SkyWalking agent open read edge in JDK 9+ failure. Shutting down.");
@@ -128,15 +135,15 @@ public static void premain(String agentArgs, Instrumentation instrumentation) th
             }
         }
 
-        agentBuilder.type(pluginFinder.buildMatch())
-                    .transform(new Transformer(pluginFinder))
+        agentBuilder.type(pluginFinder.buildMatch())//type是命中要处理的类
+                    .transform(new Transformer(pluginFinder))//transform是实际要做的修改,准确的说define的enhance
                     .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
                     .with(new RedefinitionListener())
                     .with(new Listener())
                     .installOn(instrumentation);
 
         PluginFinder.pluginInitCompleted();
-
+        //以上部分主要是注入工作，下面这个猜测主要是上报
         try {
             ServiceManager.INSTANCE.boot();
         } catch (Exception e) {

Original file line number	Diff line number	Diff line change
`@@ -86,7 +86,7 @@ public AgentClassLoader(ClassLoader parent) throws AgentPackageNotFoundException`
`86`	`86`	`super(parent);`
`87`	`87`	`File agentDictionary = AgentPackagePath.getPath();`
`88`	`88`	`classpath = new LinkedList<>();`
`89`		`- //将jar包加到类路径`
	`89`	`+ //将jar包加到类路径；MOUNT（"plugins", "activations"）`
`90`	`90`	`Config.Plugin.MOUNT.forEach(mountFolder -> classpath.add(new File(agentDictionary, mountFolder)));`
`91`	`91`	`}`
`92`	`92`