使用Java監控工具出現 Can't attach to the process

問題重現

       ➜ jinfo -flags 3032 
     
       Attaching to process ID 3032, please wait... 
     
       Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can 
      't attach to the process 
     
       sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal 
      $LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:163) 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach(LinuxDebuggerLocal.java:278) 
     
       at sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:671) 
     
       at sun.jvm.hotspot.HotSpotAgent.setupDebuggerLinux(HotSpotAgent.java:611) 
     
       at sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:337) 
     
       at sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:304) 
     
       at sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:140) 
     
       at sun.jvm.hotspot.tools.Tool.start(Tool.java:185) 
     
       at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118) 
     
       at sun.jvm.hotspot.tools.JInfo.main(JInfo.java:138) 
     
       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
     
       at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
     
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
     
       at java.lang.reflect.Method.invoke(Method.java:483) 
     
       at sun.tools.jinfo.JInfo.runTool(JInfo.java:108) 
     
       at sun.tools.jinfo.JInfo.main(JInfo.java:76) 
     
       Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can 
      't attach to the process 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach0(Native Method) 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.access$100(LinuxDebuggerLocal.java:62) 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1AttachTask.doit(LinuxDebuggerLocal.java:269) 
     
       at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLocal.java:138)

解決辦法

1	echo 0 \| sudo tee /proc/sys/kernel/yama/ptrace_scope

再次執行時就能夠獲得結果了

       ➜ jinfo -flags 3032 
     
       Attaching to process ID 3032, please wait... 
     
       Debugger attached successfully. 
     
       Server compiler detected. 
     
       JVM version is 25.5-b02 
     
       Non-default VM flags: -XX:InitialHeapSize=41943040 -XX:MaxHeapSize=536870912 -XX:MaxNewSize=178782208 -XX:M 
      inHeapDeltaBytes=524288 -XX:NewSize=1572864 -XX:OldSize=40370176 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC 
     
       Command line: -Dosgi.requiredJavaVersion=1.6 -XX:MaxPermSize=256m -Xms40m -Xmx512m

緣由

這是由於新版的Linux系統加入了 ptrace-scope 機制. 這種機制爲了防止用戶訪問當前正在運行的進程的內存和狀態, 而一些調試軟件自己就是利用 ptrace 來進行獲取某進程的內存狀態的(包括GDB),因此在新版本的Linux系統, 默認狀況下不容許再訪問了. 能夠臨時開啓. 如:java

1	echo 0 > /proc/sys/kernel/yama/ptrace_scope

永久寫到文件來持久化:linux

       emacs /etc/sysctl.d/10-ptrace.conf 
     
       添加或修改成如下這一句:(0:容許, 1:不容許) 
     
       kernel.yama.ptrace_scope = 0