基于Java Agent的attach方式實現(xiàn)方法耗時監(jiān)控

在上一篇中我們已經(jīng)介紹了java agent的相關(guān)概念和思想，給出了premain方式的實現(xiàn)代碼。本篇主要是實現(xiàn)了attach方式，不同之處主要如下:

  1. premain是靜態(tài)修改，在類加載之前修改; attach是動態(tài)修改，在類加載后修改
  2. 要使premain生效重啟應(yīng)用，而attach不重啟應(yīng)用即可修改字節(jié)碼并讓其重新加載

可以看到attach的方式更加強大，其核心原理首先是找到相關(guān)的進程id, 然后根據(jù)進程id去動態(tài)修改相關(guān)字節(jié)碼，具體的修改方式和premain無差，下面就直接給出詳細(xì)實現(xiàn)。

項目結(jié)構(gòu)(此處為了方便把主程序和Agent程序放在一起, 實際生產(chǎn)中肯定是分開的):

agentdemo
├── pom.xml
└── src
    └── main
        ├── java
        │   └── com
        │       └── hebh
        │           └── demo
        │               ├── agent
        │               │   ├── MyInstrumentationAgent.java
        │               │   └── MyTransformer.java
        │               └── application
        │                   ├── AgentLoader.java
        │                   ├── Launcher.java
        │                   ├── MyApplication.java
        │                   └── Runner.java
        └── resources
            ├── META-INF
            │   └── MANIFEST.MF
            └── log4j2.xml

先看測試結(jié)果:

  1. 打成jar包

    mvn clean package

  2. 運行主程序

    java -jar target/myAgent-jar-with-dependencies.jar

  3. 運行agent程序, 注意帶上系統(tǒng)的lib目錄

    java -Djava.ext.dirs=${JAVA_HOME}/lib -jar target/myAgent-jar-with-dependencies.jar LoadAgent

    如下圖所示，可以看到首先找到主程序的進程id為4477，然后再attach上去

image-20190126202600306

然后此時再看主程序的運行日志, 可以看到在attach后動態(tài)增加的字節(jié)碼生效了，實現(xiàn)了方法耗時監(jiān)控:

image-20190126203002824

詳細(xì)代碼:

MANIFEST.MF

Main-Class: com.hebh.demo.application.Launcher
Agent-Class: com.hebh.demo.agent.MyInstrumentationAgent
Can-Redefine-Classes: true
Can-Retransform-Classes: true

pom

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.hebh</groupId>
    <artifactId>agent-demo</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>A custom project using myfaces</name>
    <url>http://www.myorganization.org</url>

    <build>
        <finalName>myAgent</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <archive>
                        <!--避免MANIFEST.MF被覆蓋-->
                        <manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>
                    </archive>
                    <descriptorRefs>
                        <!--打包時加入依賴-->
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id> <!-- this is used for inheritance merges -->
                        <phase>package</phase> <!-- bind to the packaging phase -->
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <!-- Project dependencies -->
    <dependencies>
        <dependency>
            <groupId>com.sun</groupId>
            <artifactId>tools</artifactId>
            <version>1.8</version>
            <scope>system</scope>
            <systemPath>${java.home}/../lib/tools.jar</systemPath>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.javassist/javassist -->
        <dependency>
            <groupId>org.javassist</groupId>
            <artifactId>javassist</artifactId>
            <version>3.24.1-GA</version>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.11.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.11.1</version>
        </dependency>
    </dependencies>
</project>

主程序和Agent程序的路由:

public class Launcher {
    public static void main(String[] args) throws Exception {
        if(args != null && args.length > 0 && "LoadAgent".equals(args[0])) {
            new AgentLoader().run();
        }else{
            new MyApplication().run();
        }
    }
}

主程序部分:

public class MyApplication {
    private static Logger logger = LogManager.getLogger(MyApplication.class);

    public static void run() throws Exception {
        logger.info("[Application] Starting My application");
        Runner runner = new Runner();
        for(;;){
            runner.run();
        }
    }
}

public class Runner {
    private static final Logger logger = LogManager.getLogger(Runner.class);
    public void run() throws InterruptedException{
        long sleep = (long)(Math.random() * 1000 + 200);
        Thread.sleep(sleep);
        logger.info("run in [{}] millis!", sleep);
    }
}

Agent部分:

public class AgentLoader {
    private static Logger logger = LogManager.getLogger(AgentLoader.class);

    public static void run() {
        //指定jar路徑
        String agentFilePath = "/Users/baohuahe/demos/agentdemo/target/myAgent-jar-with-dependencies.jar";
        
        //需要attach的進程標(biāo)識
        String applicationName = "myAgent";

        //查到需要監(jiān)控的進程
        Optional<String> jvmProcessOpt = Optional.ofNullable(VirtualMachine.list()
                .stream()
                .filter(jvm -> {
                    logger.info("jvm:{}", jvm.displayName());
                    return jvm.displayName().contains(applicationName);
                })
                .findFirst().get().id());

        if(!jvmProcessOpt.isPresent()) {
            logger.error("Target Application not found");
            return;
        }
        File agentFile = new File(agentFilePath);
        try {
            String jvmPid = jvmProcessOpt.get();
            logger.info("Attaching to target JVM with PID: " + jvmPid);
            VirtualMachine jvm = VirtualMachine.attach(jvmPid);
            jvm.loadAgent(agentFile.getAbsolutePath());
            jvm.detach();
            logger.info("Attached to target JVM and loaded Java agent successfully");
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

}

public class MyInstrumentationAgent {
    private static Logger logger = LogManager.getLogger(MyInstrumentationAgent.class);

    public static void agentmain(String agentArgs, Instrumentation inst) {
        logger.info("[Agent] In agentmain method");

        //需要監(jiān)控的類
        String className = "com.hebh.demo.application.Runner";
        transformClass(className, inst);
    }

    private static void transformClass(String className, Instrumentation instrumentation) {
        Class<?> targetCls = null;
        ClassLoader targetClassLoader = null;
        // see if we can get the class using forName
        try {
            targetCls = Class.forName(className);
            targetClassLoader = targetCls.getClassLoader();
            transform(targetCls, targetClassLoader, instrumentation);
            return;
        } catch (Exception ex) {
            logger.error("Class [{}] not found with Class.forName");
        }
        // otherwise iterate all loaded classes and find what we want
        for(Class<?> clazz: instrumentation.getAllLoadedClasses()) {
            if(clazz.getName().equals(className)) {
                targetCls = clazz;
                targetClassLoader = targetCls.getClassLoader();
                transform(targetCls, targetClassLoader, instrumentation);
                return;
            }
        }
        throw new RuntimeException("Failed to find class [" + className + "]");
    }

    private static void transform(Class<?> clazz, ClassLoader classLoader, Instrumentation instrumentation) {
        MyTransformer dt = new MyTransformer(clazz.getName(), classLoader);
        instrumentation.addTransformer(dt, true);
        try {
            instrumentation.retransformClasses(clazz);
        } catch (Exception ex) {
            throw new RuntimeException("Transform failed for class: [" + clazz.getName() + "]", ex);
        }
    }

}

public class MyTransformer implements ClassFileTransformer {
    private static Logger logger = LogManager.getLogger(MyTransformer.class);

    //需要監(jiān)控的方法
    private static final String WITHDRAW_MONEY_METHOD = "run";

    /** The internal form class name of the class to transform */
    private String targetClassName;
    /** The class loader of the class we want to transform */
    private ClassLoader targetClassLoader;

    public MyTransformer(String targetClassName, ClassLoader targetClassLoader) {
        this.targetClassName = targetClassName;
        this.targetClassLoader = targetClassLoader;
    }

    @Override
    public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
                            ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
        byte[] byteCode = classfileBuffer;
        String finalTargetClassName = this.targetClassName.replaceAll("\\.", "/"); //replace . with /
        if (!className.equals(finalTargetClassName)) {
            return byteCode;
        }

        if (className.equals(finalTargetClassName) && loader.equals(targetClassLoader)) {
            logger.info("[Agent] Transforming class" + className);
            try {
                ClassPool cp = ClassPool.getDefault();
                CtClass cc = cp.get(targetClassName);
                CtMethod m = cc.getDeclaredMethod(WITHDRAW_MONEY_METHOD);

                // 開始時間
                m.addLocalVariable("startTime", CtClass.longType);
                m.insertBefore("startTime = System.currentTimeMillis();");

                StringBuilder endBlock = new StringBuilder();

                // 結(jié)束時間
                m.addLocalVariable("endTime", CtClass.longType);
                endBlock.append("endTime = System.currentTimeMillis();");

                // 時間差
                m.addLocalVariable("opTime", CtClass.longType);
                endBlock.append("opTime = endTime-startTime;");

                // 打印方法耗時
                endBlock.append("logger.info(\"completed in:\" + opTime + \" millis!\");");

                m.insertAfter(endBlock.toString());

                byteCode = cc.toBytecode();
                cc.detach();
            } catch (Exception e) {
                logger.error("Exception", e);
            }
        }
        return byteCode;
    }
}
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