btrace学习总结

当程序结果出现异常情况，但是没有日志报错的情况下,btrace成了最后的救命稻草。本文对btrace的使用进行总结。

首先推荐官方用户手册：https://kenai.com/projects/btrace/pages/UserGuide

 

btrace使用方法  

 命令格式: 

btrace [-I <include-path>] [-p <port>] [-cp <classpath>] <pid> <btrace-script> [<args>] 

 示例: 

btrace -cp common.jar  1200 AllCalls1.java 

注: common.jar不是必须的，如果只是打印耗时不需要

参数含义: 

• include-path指定头文件的路径，用于脚本预处理功能，可选； 
• port指定BTrace agent的服务端监听端口号，用来监听clients，默认为2020，可选； 
• classpath用来指定类加载路径，默认为当前路径，可选； 
• pid表示进程号，可通过jps命令获取； 
• btrace-script即为BTrace脚本；btrace脚本如果以.java结尾，会先编译再提交执行。可使用btracec命令对脚本进行预编译。 
• args是BTrace脚本参数，在脚本中可通过"$"和"$length"获取参数信息，可选；

btrace案例

1. 一次奇异的getRegionInfo异常定位
2. perftools查看堆外内存并解决hbase内存溢出
3. btrace记忆
4. 使用Btrace查看某个线程池活跃线程大小

常见使用场景 

0.最常用的情况，查看某个方法耗时：

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.Return;
import com.sun.btrace.annotations.Self;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;

@BTrace
public class IndexSearcher {

	 @TLS static long beginTime=0;  

	 
	@OnMethod(clazz="com.taobao.tlog.servlet.DataChartAction_Curve", method="execute")
	public static void test(){
    		 beginTime=timeMillis();
		
   	}		


	@OnMethod(clazz="com.taobao.tlog.servlet.DataChartAction_Curve", method="execute",location=@Location(Kind.RETURN))
	public static void test_end()throws Exception {
		println(strcat(strcat("Search .execute time is:",str(timeMillis()-beginTime)),"ms"));
		
	}
}

 如果没有打印可能出现的问题是：

1. interface是不会打印的，clazz请填写具体的实现类（已代码验证过）

1.获取方法参数值和返回值

import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class TracingScript {
   @OnMethod(
      clazz="com.learnworld.Counter",
      method="add",
      location=@Location(Kind.RETURN)
   )
   public static void traceExecute(int num,@Return int result){
     println("====== ");
     println(strcat("parameter num: ",str(num)));
     println(strcat("return value:",str(result)));
   }
}

  

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.Return;
import com.sun.btrace.annotations.Self;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
import com.taobao.eagleeye.model.RpcBased;

@BTrace(unsafe=true) 
public class EgTest2 {

	@OnMethod(clazz="com.taobao.eagleeye.data.ip.IpAppMapper", method="getAppName",location=@Location(Kind.RETURN))
	public static void search(String ip,@Return String result){
		println(strcat(ip,result));
   	}		


}

 

2.定时获取Counter类的属性值totalCount。 

import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class TracingScript {
   private static Object totalCount = 0;
   
   @OnMethod(
      clazz="com.learnworld.Counter",
      method="add",
      location=@Location(Kind.RETURN)
   ) 
   public static void traceExecute(@Self com.learnworld.Counter counter){
     totalCount = get(field("com.learnworld.Counter","totalCount"), counter);
   } 
    
   @OnTimer(1000)
   public static void print(){
     println("====== ");
     println(strcat("totalCount: ",str(totalCount)));
   }
}

 

 3. 获取add方法执行时间。

import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class TracingScript {
   @TLS private static long startTime = 0;
   
   @OnMethod(
      clazz="com.learnworld.Counter",
      method="add"
   ) 
   public static void startExecute(){
     startTime = timeNanos();
   } 
    
   @OnMethod(
      clazz="com.learnworld.Counter",
      method="add",
      location=@Location(Kind.RETURN)
   ) 
   public static void endExecute(@Duration long duration){
     long time = timeNanos() - startTime;
     println(strcat("execute time(nanos): ", str(time)));
     println(strcat("duration(nanos): ", str(duration)));
   } 
}

 

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.Return;
import com.sun.btrace.annotations.Self;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
import org.apache.lucene.search.*;
import org.apache.lucene.index.*;

@BTrace
public class MultiTermQueryWrapperFilter {

	 @TLS static long beginTime=0;  

	@OnMethod(clazz="org.apache.lucene.search.MultiTermQueryWrapperFilter", method="getDocIdSet")
	public static void traceExecuteBegin(){
    		 beginTime=timeMillis();
   	}		


	@OnMethod(clazz="org.apache.lucene.search.MultiTermQueryWrapperFilter", method="getDocIdSet",location=@Location(Kind.RETURN))
	public static void mergeArray()throws Exception {
		println(strcat(strcat("MultiTermQueryWrapperFilter .execute time is:",str(timeMillis()-beginTime)),"ms"));
	}
}

 

 

4. 获取add()方法调用方法sleep()次数。 

import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class TracingScript {
   private static long count; 
     
   @OnMethod(
      clazz="/.*/",
      method="add",
      location=@Location(value=Kind.CALL, clazz="/.*/", method="sleep")
   )
   public static void traceExecute(@ProbeClassName String pcm, @ProbeMethodName String pmn,
   @TargetInstance Object instance,  @TargetMethodOrField String method){
     println("====== ");
     println(strcat("ProbeClassName: ",pcm));
     println(strcat("ProbeMethodName: ",pmn));
     println(strcat("TargetInstance: ",str(classOf(instance))));
     println(strcat("TargetMethodOrField : ",str(method)));
     count++;
   }
   
   @OnEvent
   public static void getCount(){
       println(strcat("count: ", str(count)));
   }
}

 

3. 获取参数的成员变量

@BTrace
public class OracleTimeoutTracer {

    @OnMethod(clazz = "oracle.net.nt.ConnStrategy", method = "createSocketOptions", location = @Location(value = Kind.ENTRY))
    public static void strategy(@Self Object self, Properties paramProperties) {
        println(str(paramProperties));
    }

    @OnMethod(clazz = "oracle.net.nt.TcpNTAdapter", method = "connect", location = @Location(value = Kind.ENTRY))
    public static void adapter(@Self Object self) {
        Field socketTimeoutField = field("oracle.net.nt.TcpNTAdapter", "sockTimeout");
        Field hostField = field("oracle.net.nt.TcpNTAdapter", "host");
        Field portField = field("oracle.net.nt.TcpNTAdapter", "port");
        int scoketTimeout = (Integer) get(socketTimeoutField, self);
        int port = (Integer) get(portField, self);
        String host = (String) get(hostField, self);

        println(strcat(strcat(strcat(strcat(strcat("host : ", host), ", port : "), str(port)), " , socketTimeout : "),
                       str(scoketTimeout)));
    }
}

 

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.Return;
import com.sun.btrace.annotations.Self;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
import com.taobao.eagleeye.model.RpcBased;

@BTrace(unsafe=true) 
public class EgTest1 {

	@OnMethod(clazz="com.taobao.eagleeye.digest.RealtimeDigester", method="generateStat")
	public static void search(RpcBased rpcBased){

		Object clientAppName = get(field("com.taobao.eagleeye.model.RpcBased","clientAppName"), rpcBased);
		Object serverAppName = get(field("com.taobao.eagleeye.model.RpcBased","serverAppName"), rpcBased);
		Object serviceId = get(field("com.taobao.eagleeye.model.RpcBased","serviceId"), rpcBased);
		Object host = 	get(field("com.taobao.eagleeye.model.RpcBased","host"), rpcBased);

		String a = strcat(str(clientAppName),",");
		String b = strcat(str(serverAppName),",");
		String c = strcat(str(serviceId),",");	
		String e = strcat(str(host),",");

		String n1 = strcat(a,b);
		String n2 = strcat(c,e);
		println(strcat(n1,n2));


   	}		


}

 

 

 问题总结

 

1. btrace报错：Port 2020 unavailable

admin@eagleeyetlog128031 bin]$ ./btrace -cp eagleeye-common.jar 122810 EgTest1.java 
Port 2020 unavailable.

原因是btrace会在remote JVM(pid:122810)agent开启一个远程socketserver，默认端口是2020，正好我这台服务器有多个JVM实例，当我在第一个JVM上执行之后，第一个就会报错。正确的做法是：./btrace -cp eagleeye-common.jar -p 2021 53523 EgTest1.java 。

 

2. btrace报错：method calls are not allowed - only calls to BTraceUtils are allowed

原因是btrace存在安全限制，不允许调用被agent对象的方法。晚上说可以通过设计Dcom.sun.btrace.unsafe=true破解btrace的安全限制，但我试过不行。

 

3. 私有方法的访问

private method可以被直接访问到的

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.Return;
import com.sun.btrace.annotations.Self;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
import com.taobao.eagleeye.model.RpcBased;
import com.taobao.tlog.keyvalue.KVRecord;
import com.taobao.eagleeye.rt.DigestLogContext;

@BTrace(unsafe=true)
public class EgTest4 {

        @OnMethod(clazz="com.taobao.eagleeye.digest.RealtimeDigester", method="fastFilter")
        public static void search(DigestLogContext context){
                println("haha");
        }


}

这个方法是private,但会打印