DTraceing Apache Tomcat Server

Dtrace Support as been added to Java SE 6 Hotspot VM . The hotspot and hotspot_jni provider are used to probe the JVM internal states as well as java application. Since Apache Tomcat server is a java application, we can use hotspot provider to analysis the Tomcat server as well as the web application it is running.

To use DTrace with Tomcat server do the following step.

1 . Start the Apache Tomcat server.

bash-3.00$ startup.sh

Using CATALINA_BASE: /opt/apache-tomcat-6.0.14

Using CATALINA_HOME: /opt/apache-tomcat-6.0.14

Using CATALINA_TMPDIR: /opt/apache-tomcat-6.0.14/temp

Using JRE_HOME: /usr/jdk/instances/jdk1.6

2. Find the process id(PID) of the tomcat server and use the following the command

    bash-3.00$ jinfo -flag +ExtendedDTraceProbes XXXX

    

    in the place of XXXX use the PID of the tomcat server.

This command is used to enable the method-entry and method-return probe.

3. u are done. Run the dtrace script.

    Example

    #!/usr/sbin/dtrace -qs

dtrace:::BEGIN

{

        printf("Tracing... Hit Ctrl-C to end.\n");

}    

 

hotspot*:::method-entry

{

        self->indent++;

        printf("%*s %s %s.%s\n",self->indent,"","->", stringof(copyin(arg1, arg2)), stringof(copyin(arg3, arg4)));

        this->class = (char *) copyin(arg1, arg2 + 1);

        this->class[arg2] = '\0';

        this->method = (char *) copyin(arg3, arg4 + 1);

        this->class[arg4] = '\0';

        @calls[stringof(this->class), stringof(this->method)] = count();

}

 

hotspot*:::method-return

{

        printf("%*s %s %s.%s\n", self->indent, "", "<-", stringof(copyin(arg1, arg2)), stringof(copyin(arg3, arg4)));

        self->indent--;

}

 

dtrace:::END

{

        printa("%48s.%-24s %@4d\n",@calls);

}

    

 

DTrace Script

Dtrace Code

Yesterday i wrote some Dtrace code which i am posting here.

 

1). The probe are fired as you type some in the bash shell terminal

 

    #! /usr/sbin/dtrace -s

    syscall::write:entry

    /execname =="bash"/

    {

        printf("bash with pid %d called write system call\n", pid);

    }

2). This script display the detail of the application currently opened

    #!/usr/sbin/dtrace -s

    proc:::exec-success

    {

        printf("%s(pid=%d) started by uid - %d\n", execname, pid,uid);

    }

3).The scrip displace the how many time the process is switched between the thread in the system

    #!/usr/sbin/dtrace -s

    sysinfo:::pswitch

    {

        @[execname] = count();

    }

 

4)    This scrip display the ustack of all the process running in the system.

    #!/usr/sbin/dtrace -s

    syscall::write:entry

    {

        @[ustack()]=count();

    }

    ustack list the all the sub-process associated with the main process the last time in the ustack is the main process for example consider the fallowing ustack

libc.so.1`_write+0x15

libX11.so.4`_X11TransSocketWrite+0x25

libX11.so.4`_X11TransWrite+0x17

libX11.so.4`_XFlushInt+0x7d

libX11.so.4`_XFlush+0x10

libX11.so.4`_XEventsQueued+0x2a

libX11.so.4`XPending+0x42

libgdk-x11-2.0.so.0.1000.12`_gdk_events_queue+0xf8

libgdk-x11-2.0.so.0.1000.12`gdk_event_dispatch+0x2e

libglib-2.0.so.0.1200.12`g_main_dispatch+0x1d9

libglib-2.0.so.0.1200.12`g_main_context_dispatch+0x85

libglib-2.0.so.0.1200.12`g_main_context_iterate+0x3ce

libglib-2.0.so.0.1200.12`g_main_loop_run+0x1b8

libgtk-x11-2.0.so.0.1000.12`gtk_main+0xb2

libwidget_gtk2.so`__1cKnsAppShellDRun6M_I_+0x34

libtoolkitcomps.so`__1cMnsAppStartupDRun6M_I_+0x2b

firefox-bin`XRE_main+0x25f4

firefox-bin`main+0x25

firefox-bin`_start+0x7a

in this stack the firefox-bin is the main process.

I found its interesting the we can Send Blog from MS Word 2007

Just create a new blog post and send it to the Blog space . MS word ask from the user name and password on the Blog site

 

Its fun