參考資料
用過[Arthas]的都知道，Arthas是alibaba開源的一個非常強大的Java診斷工具。
不管是線上還是線下，我們都可以用Arthas分析程式的執行緒狀態、檢視jvm的實時執行狀態、列印方法的出入參和返回型別、收集方法中每個程式碼塊耗時，
甚至可以監控類、方法的呼叫次數、成功次數、失敗次數、平均響應時長、失敗率等。
前幾天學習java動態位元組碼技術時，突然想起這款java診斷工具的trace功能：列印方法中每個節點的呼叫耗時。簡簡單單的，正好拿來做動態位元組碼入門學習的demo。
程式結構
src ├── agent-package.bat ├── java │ ├── asm │ │ ├── MANIFEST.MF │ │ ├── TimerAgent.java │ │ ├── TimerAttach.java │ │ ├── TimerMethodVisitor.java │ │ ├── TimerTrace.java │ │ └── TimerTransformer.java │ └── demo │ ├── MANIFEST.MF │ ├── Operator.java │ └── Test.java ├── run-agent.bat ├── target-package.bat └── tools.jar
編寫目標程式
程式碼
package com.gravel.demo.test.asm;
/**
* @Auther: syh
* @Date: 2020/10/12
* @Description:
*/
public class Test {
public static boolean runnable = true;
public static void main(String[] args) throws Exception {
while (runnable) {
test();
}
}
// 目標：分析這個方法中每個節點的耗時
public static void test() throws Exception {
Operator.handler();
long time_wait = (long) ((Math.random() * 1000) + 2000);
Operator.callback();
Operator.pause(time_wait);
}
}
Operator.java
/**
* @Auther: syh
* @Date: 2020/10/28
* @Description: 輔助類，同樣可用於分析耗時
*/
public class Operator {
public static void handler() throws Exception {
long time_wait = (long) ((Math.random() * 10) + 20);
sleep(time_wait);
}
public static void callback() throws Exception {
long time_wait = (long) ((Math.random() * 10) + 20);
sleep(time_wait);
}
public static void pause(long time_wait) throws Exception {
sleep(time_wait);
}
public static void stop() throws Exception {
Test.runnable = false;
System.out.println("business stopped.");
}
private static void sleep(long time_wait) throws Exception {
Thread.sleep(time_wait);
}
}
MANIFEST.MF
編寫MANIFEST.MF檔案，指定main-class。注意：冒號後面加空格，結尾加兩行空白行。
Manifest-Version: 1.0 Archiver-Version: Plexus Archiver Built-By: syh Created-By: Apache Maven Build-Jdk: 1.8.0_202 Main-Class: com.gravel.demo.test.asm.Target
打包
偷懶寫了bat批命令，生成target.jar
@echo off & setlocal attrib -s -h -r -a /s /d demo rd /s /q demo rd /q target.jar javac -encoding utf-8 -d . ./java/demo/*.java jar cvfm target.jar ./java/demo/MANIFEST.MF demo rd /s /q demo pause java -jar target.jar
java agent探針
instrument 是 JVM 提供的一個可以修改已載入類檔案的類庫。而要實現程式碼的修改，我們需要實現一個 instrument agent。
jdk1.5時，agent有個內定方法premain。是在類載入前修改。所以無法做到修改正在執行的類。
jdk1.6後，agent新增了agentmain方法。agentmain是在虛擬機器啟動以後載入的。所以可以做攔截、熱部署等。
講JAVA探針技術，實際上我自己也是半吊子。所以這裡用的是邊分析別人例子邊摸索的思路來實現我的簡單的trace功能。
例子使用的是ASM位元組碼生成框架
MANIFEST.MF
首先一個可用的jar，關鍵之一是MAINFEST.MF檔案是吧。
Manifest-Version: 1.0 Archiver-Version: Plexus Archiver Created-By: Apache Maven Built-By: syh Build-Jdk: 1.8.0_202 Agent-Class: asm.TimerAgent Can-Retransform-Classes: true Can-Redefine-Classes: true Class-Path: ./tools.jar Main-Class: asm.TimerAttach
我們從MANIFEST.MF中提取幾個關鍵的屬性
屬性
|
說明 |
|
Agent-Class |
agentmain入口類
|
|
Premain-Class |
premain入口類，與agent-class至少指定一個。 |
|
Can-Retransform-Classes |
對於已經載入的類重新進行轉換處理，即會觸發重新載入類定義。 |
|
Can-Redefine-Classes |
對已經載入的類不做轉換處理，而是直接把處理結果(bytecode)直接給JVM |
|
Class-Path |
asm動態位元組碼技術依賴tools.jar，如果沒有可以從jdk的lib目錄下拷貝。 |
|
Main-Class |
這裡並不是agent的關鍵屬性，為了方便，我把載入虛擬機器的程式和agent合併了。 |
程式碼
然後我們來看看兩個入口類，首先分析一個可執行jar的入口類Main-Class。
public class TimerAttach {
public static void main(String[] args) throws Exception {
/**
* 啟動jar時，需要指定兩個引數：1目標程式的pid。 2 要修改的類路徑及方法，格式 package.class#methodName
*/
if (args.length < 2) {
System.out.println("pid and class must be specify.");
return;
}
if (!args[1].contains("#")) {
System.out.println("methodName must be specify.");
return;
}
VirtualMachine vm = VirtualMachine.attach(args[0]);
// 這裡為了方便我把 vm和agent整合在一個jar裡面了， args[1]就是agentmain的入參。
vm.loadAgent("agent.jar", args[1]);
}
}
程式碼很簡單，1：args入參校驗；2：載入目標程式pid(args[0])；3：載入agent jar包（因為合併了，所以這個jar其實就是自己）。
其中vm.loadAgent(agent.jar, args[1])會呼叫agent-class中的agentmain方法，而args[1]就是agentmain的第一個入參。
public class TimerAgent {
public static void agentmain(String agentArgs, Instrumentation inst) {
String[] ownerAndMethod = agentArgs.split("#");
inst.addTransformer(new TimerTransformer(ownerAndMethod[1]), true);
try {
inst.retransformClasses(Class.forName(ownerAndMethod[0]));
System.out.println("agent load done.");
} catch (Exception e) {
e.printStackTrace();
System.out.println("agent load failed!");
}
}
}
在 agentmain 方法裡，我們呼叫retransformClassess方法載入目標類，呼叫addTransformer方法載入TimerTransformer類實現對目標類的重新定義。
類轉換器
public class TimerTransformer implements ClassFileTransformer {
private String methodName;
public TimerTransformer(String methodName) {
this.methodName = methodName;
}
@Override
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classFileBuffer) {
ClassReader reader = new ClassReader(classFileBuffer);
ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_MAXS);
ClassVisitor classVisitor = new TimerTrace(Opcodes.ASM5, classWriter, methodName);
reader.accept(classVisitor, ClassReader.EXPAND_FRAMES);
return classWriter.toByteArray();
}
}
對被匹配到的類中的方法進行修改
public class TimerTrace extends ClassVisitor implements Opcodes {
private String owner;
private boolean isInterface;
private String methodName;
public TimerTrace(int i, ClassVisitor classVisitor, String methodName) {
super(i, classVisitor);
this.methodName = methodName;
}
@Override
public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
super.visit(version, access, name, signature, superName, interfaces);
owner = name;
isInterface = (access & ACC_INTERFACE) != 0;
}
@Override
public MethodVisitor visitMethod(int access, String name, String descriptor, String signature,
String[] exceptions) {
MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exceptions);
// 匹配到指定methodName時，進行位元組碼修改
if (!isInterface && mv != null && name.equals(methodName)) {
// System.out.println(" package.className:methodName()")
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
mv.visitInsn(DUP);
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
mv.visitLdcInsn(" " + owner.replace("/", ".")
+ ":" + methodName + "() ");
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append",
"(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
// 方法程式碼塊耗時統計並列印
TimerMethodVisitor at = new TimerMethodVisitor(owner, access, name, descriptor, mv);
return at.getLocalVariablesSorter();
}
return mv;
}
public static void main(String[] args) throws IOException {
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
TraceClassVisitor tv = new TraceClassVisitor(cw, new PrintWriter(System.out));
TimerTrace addFiled = new TimerTrace(Opcodes.ASM5, tv, "test");
ClassReader classReader = new ClassReader("demo.Test");
classReader.accept(addFiled, ClassReader.EXPAND_FRAMES);
File file = new File("out/production/asm-demo/demo/Test.class");
String parent = file.getParent();
File parent1 = new File(parent);
parent1.mkdirs();
file.createNewFile();
FileOutputStream fileOutputStream = new FileOutputStream(file);
fileOutputStream.write(cw.toByteArray());
}
}
要統計方法中每行程式碼耗時，只需要在每一行程式碼的前後加上當前時間戳然後相減即可。
所以我們的程式碼是這麼寫的。
public class TimerMethodVisitor extends MethodVisitor implements Opcodes {
private int start;
private int end;
private int maxStack;
private String lineContent;
public boolean instance = false;
private LocalVariablesSorter localVariablesSorter;
private AnalyzerAdapter analyzerAdapter;
public TimerMethodVisitor(String owner, int access, String name, String descriptor, MethodVisitor methodVisitor) {
super(Opcodes.ASM5, methodVisitor);
this.analyzerAdapter = new AnalyzerAdapter(owner, access, name, descriptor, this);
localVariablesSorter = new LocalVariablesSorter(access, descriptor, this.analyzerAdapter);
}
public LocalVariablesSorter getLocalVariablesSorter() {
return localVariablesSorter;
}
/**
* 進入方法後，最先執行
* 所以我們可以在這裡定義一個最開始的時間戳, 然後建立一個區域性變數var_end
* Long var_start = System.nanoTime();
* Long var_end;
*/
@Override
public void visitCode() {
mv.visitCode();
mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "nanoTime", "()J", false);
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;", false);
start = localVariablesSorter.newLocal(Type.LONG_TYPE);
mv.visitVarInsn(ASTORE, start);
end = localVariablesSorter.newLocal(Type.LONG_TYPE);
maxStack = 4;
}
/**
* 在每行程式碼後面增加以下程式碼
* var_end = System.nanoTime();
* System.out.println("[" + String.valueOf((var_end.doubleValue() - var_start.doubleValue()) / 1000000.0D) + "ms] " + "package.className:methodName() #lineNumber");
* var_start = var_end;
* @param lineNumber
* @param label
*/
@Override
public void visitLineNumber(int lineNumber, Label label) {
super.visitLineNumber(lineNumber, label);
if (instance) {
mv.visitMethodInsn(INVOKESTATIC, "java/lang/System", "nanoTime", "()J", false);
mv.visitMethodInsn(INVOKESTATIC, "java/lang/Long", "valueOf", "(J)Ljava/lang/Long;", false);
mv.visitVarInsn(ASTORE, end);
// System.out
mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
// new StringBuilder();
mv.visitTypeInsn(NEW, "java/lang/StringBuilder");
mv.visitInsn(DUP);
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false);
mv.visitLdcInsn(" -[");
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append",
"(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
mv.visitVarInsn(ALOAD, end);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Long", "doubleValue", "()D", false);
mv.visitVarInsn(ALOAD, start);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Long", "doubleValue", "()D", false);
mv.visitInsn(DSUB);
mv.visitLdcInsn(new Double(1000 * 1000));
mv.visitInsn(DDIV);
// String.valueOf((end - start)/1000000)
mv.visitMethodInsn(INVOKESTATIC, "java/lang/String", "valueOf", "(D)Ljava/lang/String;", false);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append",
"(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
mv.visitLdcInsn("ms] ");
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append",
"(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
// .append("owner:methodName() #line")
mv.visitLdcInsn(this.lineContent + "#" + lineNumber);
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append",
"(Ljava/lang/String;)Ljava/lang/StringBuilder;", false);
// stringBuilder.toString()
mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false);
// println stringBuilder.toString()
mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
// start = end
mv.visitVarInsn(ALOAD, end);
mv.visitVarInsn(ASTORE, start);
maxStack = Math.max(analyzerAdapter.stack.size() + 4, maxStack);
}
instance = true;
}
/**
* 拼接位元組碼內容
* @param opcode
* @param owner
* @param methodName
* @param descriptor
* @param isInterface
*/
@Override
public void visitMethodInsn(int opcode, String owner, String methodName, String descriptor, boolean isInterface) {
super.visitMethodInsn(opcode, owner, methodName, descriptor, isInterface);
if (!isInterface && opcode == Opcodes.INVOKESTATIC) {
this.lineContent = owner.replace("/", ".")
+ ":" + methodName + "() ";
}
}
@Override
public void visitMaxs(int maxStack, int maxLocals) {
super.visitMaxs(Math.max(maxStack, this.maxStack), maxLocals);
}
}
如果初學者不會改位元組碼。可以利用idea自帶的asm外掛做參考。
這樣，一個可執行的agent jar就寫完了，然後打包
@echo off attrib -s -h -r -a /s /d asm rd /s /q asm rd /q agent.jar javac -XDignore.symbol.file=true -encoding utf-8 -d . ./java/asm/*.java jar cvfm agent.jar ./java/asm/MANIFEST.MF asm rd /s /q asm exit
測試
執行目標程式 target.jar
java -jar target.jar
列印Test.test中每個節點耗時
java -jar agent.jar [pid] demo.Test#test
結果
列印Operator.handler方法每個節點耗時
