This chapter gives guidelines for debugging applications in the Sun Java System Application Server. It includes the following sections:
When you enable debugging, you enable both local and remote debugging. To start the server in debug mode, use the --debug option as follows:
asadmin start-domain --user adminuser --debug [domain-name]
jdb -attach 9009
jdb -connect com.sun.jdi.SocketAttach:port=9009
For more information about the jdb debugger, see the following links:
Java Platform Debugger Architecture - The Java Debugger: http://java.sun.com/products/jpda/doc/soljdb.html
Java Platform Debugger Architecture - Connecting with JDB: http://java.sun.com/products/jpda/doc/conninv.html#JDB
Application Server debugging is based on the JPDA. For more information, see JPDA Options.
You can attach to the Application Server using any JPDA compliant debugger, including that of NetBeans, Sun Java Studio, JBuilder, Eclipse, and so on.
You can enable debugging even when the application server is started without the --debug option. This is useful if you start the application server from the Windows Start Menu, or if you want to make sure that debugging is always turned on.
Use the Admin Console. In the developer profile, select the Application Server component and the JVM Settings tab. In the cluster profile, select the JVM Settings component under the relevant configuration.
To specify a different port (from 9009, the default) to use when attaching the JVM to a debugger, specify address= port-number in the Debug Options field.
To add JPDA options, add any desired JPDA debugging options in Debug Options. See JPDA Options.
For details, click the Help button in the Admin Console from the JVM Settings page.
The default JPDA options in Application Server are as follows:
For Windows, you can change dt_socket to dt_shmem.
If you substitute suspend=y, the JVM starts in suspended mode and stays suspended until a debugger attaches to it. This is helpful if you want to start debugging as soon as the JVM starts.
To specify a different port (from 9009, the default) to use when attaching the JVM to a debugger, specify address=port-number.
You can include additional options. A list of JPDA debugging options is available at http://java.sun.com/products/jpda/doc/conninv.html#Invocation.
To generate a Java stack trace for debugging, use the asadmin generate-jvm-report --type=thread command. The stack trace goes to the domain-dir/logs/server.log file and also appears on the command prompt screen. For more information about the asadmin generate-jvm-report command, see the Sun Java System Application Server 9.1 Reference Manual.
When the appclient script executes the java command to run the Application Client Container (ACC), which in turn runs the client, it includes on the command line the value of the VMARGS environment variable. You can set this variable to any suitable value. The following example debugging setup is for Windows systems:
The following example debugging setup is for UNIX-based systems:
set VMARGS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8118
For debugging an application client, you should set suspend to y so you can connect the debugger to the client before any code has actually executed. Otherwise, the client may start running and execute past the point you want to examine.
You should use different ports for the server and client if you are debugging both concurrently. For details about setting the port, see JPDA Options.
For information about the appclient script, see Sun Java System Application Server 9.1 Reference Manual.
Sun Java System Message Queue has a broker logger, which can be useful for debugging Java Message Service (JMS) applications, including message-driven bean applications. You can adjust the logger’s verbosity, and you can send the logger output to the broker’s console using the broker’s -tty option. For more information, see the Sun Java System Message Queue 4.1 Administration Guide.
To have the server logs and messages printed to System.out on your command prompt screen, you can start the server in verbose mode. This makes it easy to do simple debugging using print statements, without having to view the server.log file every time.
To start the server in verbose mode, use the --verbose option as follows:
asadmin start-domain --user adminuser --verbose [domain-name]
On Windows platforms, you must perform an extra preparation step if you want to use Ctrl-Break to print a thread dump. In the as-install/asenv.bat file, change AS_NATIVE_LAUNCHER="false" to AS_NATIVE_LAUNCHER="true".
When the server is in verbose mode, messages are logged to the console or terminal window in addition to the log file. In addition, pressing Ctrl-C stops the server and pressing Ctrl-\ (on UNIX platforms) or Ctrl-Break (on Windows platforms) prints a thread dump. On UNIX platforms, you can also print a thread dump using the jstack command (see http://java.sun.com/j2se/1.5.0/docs/tooldocs/share/jstack.html) or the command kill -QUIT process_id.
You can use the Application Server’s log files to help debug your applications. Use the Admin Console. In the developer profile, select the Application Server component. In the cluster profile, select the Stand-Alone Instances component, and select the instance from the table. Then click the View Log Files button in the General Information page.
To change logging settings in the developer profile, select the Logging tab. In the cluster profile, select Logger Settings under the relevant configuration.
For details about logging, click the Help button in the Admin Console.
You can use a profiler to perform remote profiling on the Application Server to discover bottlenecks in server-side performance. This section describes how to configure these profilers for use with the Application Server:
Information about comprehensive monitoring and management support in the JavaTM 2 Platform, Standard Edition (J2SETM platform) is available at http://java.sun.com/j2se/1.5.0/docs/guide/management/index.html.
For information on how to use the NetBeans profiler, see http://www.netbeans.org and http://blogs.sun.com/roller/page/bhavani?entry=analyzing_the_performance_of_java.
The Heap and CPU Profiling Agent (HPROF) is a simple profiler agent shipped with the Java 2 SDK. It is a dynamically linked library that interacts with the Java Virtual Machine Profiler Interface (JVMPI) and writes out profiling information either to a file or to a socket in ASCII or binary format.
HPROF can monitor CPU usage, heap allocation statistics, and contention profiles. In addition, it can also report complete heap dumps and states of all the monitors and threads in the Java virtual machine. For more details on the HPROF profiler, see the JDK documentation at http://java.sun.com/j2se/1.5.0/docs/guide/jvmpi/jvmpi.html#hprof.
After HPROF is enabled using the following instructions, its libraries are loaded into the server process.
Use the Admin Console. In the developer profile, select the Application Server component and the JVM Settings tab. In the cluster profile, select the JVM Settings component under the relevant configuration. Then select the Profiler tab.
Edit the following fields:
Profiler Name – hprof
Profiler Enabled – true
Classpath – (leave blank)
JVM Option – Select Add, type the HPROF JVM option in the Value field, then check its box. The syntax of the HPROF JVM option is as follows:
Here is an example of params you can use:
The file parameter determines where the stack dump is written.
Using help lists parameters that can be passed to HPROF. The output is as follows:
Hprof usage: -Xrunhprof[:help]|[:<option>=<value>, ...] Option Name and Value Description Default --------------------- ----------- ------- heap=dump|sites|all heap profiling all cpu=samples|old CPU usage off format=a|b ascii or binary output a file=<file> write data to file java.hprof (.txt for ascii) net=<host>:<port> send data over a socket write to file depth=<size> stack trace depth 4 cutoff=<value> output cutoff point 0.0001 lineno=y|n line number in traces? y thread=y|n thread in traces? n doe=y|n dump on exit? y
Do not use help in the JVM Option field. This parameter prints text to the standard output and then exits.
The help output refers to the parameters as options, but they are not the same thing as JVM options.
Restart the Application Server.
This writes an HPROF stack dump to the file you specified using the file HPROF parameter.
Information about JProbeTM from Sitraka is available at http://www.quest.com/jprobe/.
After JProbe is installed using the following instructions, its libraries are loaded into the server process.
Install JProbe 22.214.171.124.
For details, see the JProbe documentation.
In the developer profile, select the Application Server component and the JVM Settings tab. In the cluster profile, select the JVM Settings component under the relevant configuration. Then select the Profiler tab.
Edit the following fields before selecting Save and restarting the server:
Profiler Name – jprobe
Profiler Enabled – true
Classpath – (leave blank)
JVM Option – For each of these options, select Add, type the option in the Value field, then check its box
If any of the configuration options are missing or incorrect, the profiler might experience problems that affect the performance of the Application Server.
When the server starts up with this configuration, you can attach the profiler.
Set the following environment variable:
See Step 6 for instructions on how to create the JPL file.
Start the server instance.
Launch the jpprofiler and attach to Remote Session. The default port is 4444.
Create the JPL file using the JProbe Launch Pad. Here are the required settings:
Select Server Side for the type of application.
On the Program tab, provide the following details:
Target Server – other-server
Server home Directory – as-install
Server class File – com.sun.enterprise.server.J2EERunner
Working Directory – as-install
Classpath – as-install/lib/appserv-rt.jar
Source File Path – source-code-dir (in case you want to get the line level details)
Server class arguments – (optional)
Main Package – com.sun.enterprise.server
You must also set VM, Attach, and Coverage tabs appropriately. For further details, see the JProbe documentation. After you have created the JPL file, use this an input to JPROBE_ARGS_0.