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Troubleshooting |
Troubleshooting
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In general an application should run as fast under the Wrapper as it does
when running standalone. Here are a few places to start looking.
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On some platforms, including Windows, sending large quantities of text to
System.out or System.err will cause the program to slow down. This is because
all of that output is being rendered to the screen in a graphics environment.
This is actually the OS eating the CPU rather than the Wrapper or your
application but the end result is the same.
To significantly reduce this effect, use a logging tool which will output to
a file rather than to stdout. By doing so the output is never sent to the
Wrapper or the user console.
Another option which is almost as good is to configure the Wrapper's console
log level, using the wrapper.console.loglevel
property, so that the output is only sent to the Wrapper's log file. Console
output is disabled by default when running as an NT service and the console has
not been enabled.
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Make sure that your system has plenty of memory for the JVM to run without
doing any disk swapping. Because of the way Java manages memory. A very
significant speed hit is common simply because Java is forced to do paging
of large amounts of its memory as it attempted to perform garbage collection.
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Strarting with version 3.0.5 of the Java Service Wrapper, the
wrapper.pidfile property was
implemented on the Windows platform. Previous versions of the Wrapper
ignored this property when running under Windows. However, if the wrapper.conf
file that you are using was created using a version of the Wrapper prior to
3.0.0 then you may have this property defined as a holdout from when you
copied the file from the example wrapper.conf. This will lead to an error
like the following:
ERROR: Could not write pid file /var/run/testwrapper.pid: The
system cannot find the path specified. (0x3)
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To resolve this simply edit your wrapper.conf file and remove the
wrapper.pidfile property.
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A few users have asked about the following message showing up in their wrapper.log file:
WARNING - Unable to load native library 'wrapper' for class WrapperManager.
System signals will not be handled correctly.
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This message is being shown because the Java component of the Wrapper was unable to
load its native libraries during initialization. If you look in your wrapper.conf
file, you will see a property, wrapper.java.library.path.
This is used to specify the directory that the Wrapper will look in to find its native
library. (Wrapper.DLL on Windows, or libwrapper.so on Unix systems) You should place
the library file in the specified directory or change the property to point to the
directory where it is located.
As of version 2.2.9 this error message was improved. You will now see something like
the following (Depending on your platform of course):
WARNING - Unable to load native library 'wrapper' because the
file 'Wrapper.DLL' could not be located in the following
java.library.path:
C:\SourceForge\wrapper\bin\..\lib
Please see the documentation for the wrapper.java.library.path
configuration property.
System signals will not be handled correctly.
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On Windows 2000 or NT, you will see the following error message if you attempt to
install a service when logged in as a user without Administrator privileges.
OpenSCManager failed - access denied.
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Solution. Contact your system administrator and beg them to install the service for
you. Easy if that is you.
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Output describing the problem should be displayed in the console as well as the
configured log file. To get more detailed output, edit your wrapper.conf file and
enable debugging by uncommenting the wrapper.debug property. This will display very
detailed output at every step in the process of launching and monitoring your
application.
If your application works when not using the Wrapper, but fails with the Wrapper,
then it is very likely that there is a problem in the way you set up your wrapper.conf
file. Please look closely at the command used to launch java, in the debug output.
It is possible that there is a mistake in the classpath or something.
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It is possible that the Wrapper is not able to locate the specified wrapper
configuration file, or it is not able to open the configured log file for some reason.
In either case, the Wrapper will log output to a file called wrapper.log in the current
working directory. The current working directory will most likely be the directory
containing the binary. However, in some cases, when running as an NT service, the
wrapper.log file may be placed in your WinNT\System32 directory.
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If you call System.exit() in your application then Wrapper will catch this and attempt
to shutdown the application cleanly. If during the shutdown process, your application
once again calls System.exit() then the call will block indefinitely causing your
application to hang. There are also problems with calling the destroy() method on an
AWT frame or window from within a shutdown hoot thread. Please take a look at the
wrapper.disable_shutdown_hook property in the Configuration File Overview for details
on how to avoid this problem.
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Most of the features of the Wrapper will work with 1.2.x JVMs so the JVM is
included on the list of supported JVMs. However, the released version of
the wrapper is built using a 1.4.x version of Java. 1.2.x versions of the
JVM have problems with the generated jar and will crash with very low level
JNI errors. This appears to be a bug in the 1.4.x versions of the compiler
as it happens even if the "1.1" JVM target is specified when compiling the
classes.
Here is an example of the errors that I have seen:
A nonfatal internal JIT (3.10.107(x)) error 'chgTarg: Conditional' has occurred in :
'org/tanukisoftware/wrapper/WrapperManager.stopCommon (II)V': Interpreting method.
Please report this error in detail to http://java.sun.com/cgi-bin/bugreport.cgi
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I get help from several people to be able to produce the releases for all
of the various supported platforms and it is not really possible to force
everyone to use old JDKs to build the Wrapper distributions.
If you are experiencing crash problems with 1.2.x JVMs and the Wrapper
please try downloading a source distribution and building the wrapper.jar
file using your 1.2.x JDK. This will fix the problem.
If you are running into this, please post a note to the wrapper-user mailing
list. I am not sure how many people are still using 1.2.x JVMs. But if
it is still fairly common, I may reconsider the above policy and look into
what it will take to get the releases built using an older JVM.
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Because the Wrapper is using a pinging mechanism to check on the health of the JVM, it
is possible that the Wrapper will think that the JVM is hung when it isn't if another
process is taking 100% of the CPU for longer than 30 seconds. This will result in an
entry like the following in your log file, and the JVM being restarted:
jvm 1 | 2001/12/01 12:23:23 | start()
wrapper | 2001/12/01 12:23:44 | Startup failed: Timed out waiting for signal from JVM.
wrapper | 2001/12/01 12:23:44 | Java Virtual Machine did not exit on request, terminated
wrapper | 2001/12/01 12:23:49 | Launching a JVM...
jvm 2 | 2001/12/01 12:23:50 | Initializing...
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The property wrapper.ping.timeout=30 in
conf/wrapper.log can be used to extend this timeout.
But be aware that this will also lengthen the amount of time that your application will
remain hung in the event of a real problem.
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by Leif Mortenson
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