[英]Java Agent using Byte-Buddy doesn't work
我需要你的幫助來找出我的實施有什么問題...
我正在嘗試使用byte-buddy實現一個簡單的JVM運行時分析器。 一般來說,我需要的是每個方法調用都將記錄在一個堆棧中,我在一個單獨的對象中管理。
在閱讀了幾篇文章之后,我明白最好使用“Advise”方法而不是“MethodDelegation”,這就是我發布的內容:
Agent.java:
package com.panaya.java.agent;
import net.bytebuddy.agent.builder.AgentBuilder;
import net.bytebuddy.asm.Advice;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.matcher.ElementMatchers;
import net.bytebuddy.utility.JavaModule;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
public class Agent {
private static List<Pattern> pkgIncl = new ArrayList<Pattern>();
private static List<Pattern> pkgExcl = new ArrayList<Pattern>();
private static void initMatcherPatterns(String argument) {
if (argument == null) {
System.out.println("Missing configuration argument");
return;
}
System.out.println("Argument is: " + argument);
String[] tokens = argument.split(";");
if (tokens.length < 1) {
System.out.println("Missing delimeter ;");
return;
}
for (String token : tokens) {
String[] args = token.split("=");
if (args.length < 2) {
System.out.println("Missing argument delimeter =:" + token);
return;
}
String argtype = args[0];
if (!argtype.equals("incl") && !argtype.equals("excl")) {
System.out.println("Wrong argument: " + argtype);
return;
}
String[] patterns = args[1].split(",");
for (String pattern : patterns) {
Pattern p = null;
System.out.println("Compiling " + argtype + " pattern:" + pattern + "$");
try {
p = Pattern.compile(pattern + "$");
} catch (PatternSyntaxException pse) {
System.out.println("pattern: " + pattern + " not valid, ignoring");
}
if (argtype.equals("incl"))
pkgIncl.add(p);
else
pkgExcl.add(p);
}
}
}
private static boolean isShouldInstrumentClass(String className) {
System.out.println("Testing " + className + " for match.");
boolean match = false;
String name = className.replace("/", ".");
for (Pattern p : pkgIncl) {
Matcher m = p.matcher(name);
if (m.matches()) {
match = true;
break;
}
}
for (Pattern p : pkgExcl) {
Matcher m = p.matcher(name);
if (m.matches()) {
match = false;
break;
}
}
if (match) {
System.out.println("Class " + name + "should be instrumented.");
} else {
System.out.println("Skipping class: " + name);
}
return match;
}
public static void premain(String agentArgument, Instrumentation instrumentation) {
System.out.println("Premain started");
try {
initMatcherPatterns(agentArgument);
new AgentBuilder.Default()
.with(AgentBuilder.TypeStrategy.Default.REBASE)
.type(new AgentBuilder.RawMatcher() {
public boolean matches(TypeDescription typeDescription, ClassLoader classLoader, JavaModule javaModule, Class<?> aClass, ProtectionDomain protectionDomain) {
return isShouldInstrumentClass(typeDescription.getActualName());
}
})
.transform((builder, typeDescription, classLoader) -> builder
.visit(Advice.to(ProfilingAdvice.class)
.on(ElementMatchers.any()))).installOn(instrumentation);
} catch (RuntimeException e) {
System.out.println("Exception instrumenting code : " + e);
e.printStackTrace();
}
}
}
和ProfilingAdvice.java:
package com.panaya.java.agent;
import com.panaya.java.profiler.MethodStackCollector;
import net.bytebuddy.asm.Advice;
public class ProfilingAdvice {
@Advice.OnMethodEnter
public static void enter(@Advice.Origin("#t.#m") String signature) {
System.out.println("OnEnter :" + signature);
try {
MethodStackCollector.getInstance().push(signature);
} catch (Exception e) {
e.printStackTrace();
}
}
@Advice.OnMethodExit
public static void exit(@Advice.Return long value) {
System.out.println("OnExit - value = " + value);
try {
MethodStackCollector.getInstance().pop();
} catch (Exception e) {
e.printStackTrace();
}
}
}
出於某種原因,ProfilingAdvice類中的“enter”和“exit”方法根本不會被調用。
我究竟做錯了什么 ?
謝謝,很高興。
我嘗試了你的例子,在減少了對print命令的退出建議后,你的匹配器只匹配了一些類foo.Bar
:
package foo;
public class Bar {
public long qux() { return 0L; }
}
儀器工作沒有問題。 當你的ProfilingAdvice
需要一個long
返回類型時,我發現你的Advice
匹配器指定any()
有點可疑。 您是否嘗試僅在您的建議中沒有任何注釋的情況下打印到控制台?
您可以通過以下方式調試此類問題:
new AgentBuilder.Default()
.with(AgentBuilder.Listener.StreamWriting.toSystemOut());
將儀器中的潛在錯誤打印到控制台。
@Advice.Return
代表監視器方法的返回值。
@Advice.Return
不是enter(@Advice.Origin("#t.#m") String signature)
方法的返回值。
所以,以下代碼是可以的:
public class ProfilerInterceptor {
public static ThreadLocal<Long> threadLocal = new ThreadLocal();
@Advice.OnMethodEnter
public static void enter(@Advice.Origin("#t.#m") String signature) {
System.out.printf("Enter: %s\n", signature);
long start = System.currentTimeMillis();
threadLocal.set(start);
try {
MethodStackCollector.getInstance().push(signature);
} catch (Exception e) {
e.printStackTrace();
}
}
@Advice.OnMethodExit
public static void exit(@Advice.Origin("#t.#m") String signature) {
long value = System.currentTimeMillis() - threadLocal.get();
System.out.printf("Exit: %s\nTime: %d\n\n", signature, value);
System.out.println("OnExit - value = " + value);
try {
MethodStackCollector.getInstance().pop();
} catch (Exception e) {
e.printStackTrace();
}
}
}
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