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WTP/HTTP Connection Tracer Diagnostic Utility

Revision as of 22:31, 25 September 2011 by David (Talk | contribs) (initial transfered draft)

HTTP Connection Tracer Diagnostic Utility

The Problem

There are times that code is seen to go to the internet to fetch something, and its not often clear why or what code is responsible. Sometimes it is necessary for code to fetch something remotely, but often it is best to keep a local cached copy, use and XML Catalog, etc., to avoid excessive internet traffic.

The solution (to help diagnosis excessive access)

There is an "HTTP Connection Tracer" tool to help detect and track when code requests an HTTP connection, so that excessive requests can be detected early, and more easily fixed.

In addition to logging request, the tool does allow a "remapping" of an HTTP request to a local file. This can help work around immediate problems but, of course, is not a long term solution.

Please address any questions, comments or suggestions in bugs or via the mailing list.


Download the HTTP connection tracer diagnostic utility jar file.

The jar file must be added to the JRE's lib/ext directory. This must be done for each JRE that you're using in your environment. So if you're developing your code with eclipse and deploying to a server (and you want to get trace information for both) you'll need to make the JAR available for both the eclipse JRE and the server's JRE.


When you launch eclipse or run your sever, you'll need to specify some vmargs to activate the "HTTP Connection Tracer" tool. Here's an example of how you'd do this on the command line for Eclipse.

 eclipse.exe -vmargs -Djava.protocol.handler.pkgs=org.eclipse.wtp.releng.www.protocol -DurlMapLocation=C:\map.txt -DurlLogLocation=C:\log.txt

Here's a description of what each argument does ....

name example value description
java.protocol.handler.pkgs org.eclipse.wtp.releng.www.protocol Tells the JVM to utilize the "HTTP Connection Tracer" tool.
urlMapLocation C:\map.txt Specifies the location of a 'properties' file where URL mapping information can be provided. Note that if no map location is specified then URL redirection never occurs.
urlLogLocation C:\log.txt Specifies the location of a log file where logging information will be written. Note that if no log location is specified the logging information will be written to System.out. [ISSUE: is the following sentence still true? The log might always be created now?] Note also that if no HTTP requests are made, then no log or output is produced. If there is no output, you may want to confirm your setup by running a small test program that explicitly does a URL connection. See bug 216524 for an example.

The Map File

Here's an example of what the map file looks like.... =file:///D:/my-schema-cache/bar.xsd

Notice its just a list of mapping pairs (separated by an '=' sign) that specifies how a web address should be redirected to a local file system address. By editing this file, a customer can workaround nagging 'going off to the internet problems' until a proper fix is delivered.

The Log File

Each time the JVM attempts to create an HTTP connection, an entry is added to the log file. Below is an example log file entry. It consists of three interesting pieces of information...

URL request - provides the URL address for the connection requested
URL mapped - provides the 'mapped' address (as specified in the 'map.txt' file) to help the customer see that the URL has been successfully redirected
STACK TRACE - dumps of stack to help the support and development teams understand the code paths involved in creating the connection request

Note that the presence of an entry in the log does not necessarily imply an defect in code. Some attempts to create an HTTP connections are expected. So I'd encourage you to scrutinize the entries in the log file. At the very least the logs will provide you some useful stack trace information that will help developers understand the nature of the HTTP connections.

Example Output

URL requested :
URL mapped : file:///D:/workspaces/corona-test/XMLExamples/substitutionGroup/Catalogue4.xsd
java.lang.Exception: dumpTheStack
   at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source) 
   at org.apache.xerces.impl.XMLVersionDetector.determineDocVersion(Unknown Source) 
   at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) 
   at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source) 
   at org.apache.xerces.parsers.XMLParser.parse(Unknown Source) 
   at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source) 
   at javax.xml.parsers.SAXParser.parse(Unknown Source) 
   at org.eclipse.xsd.util.XSDParser.parse( 
   at org.eclipse.jface.operation.ModalContext.runInCurrentThread( 
   at org.eclipse.jface.wizard.WizardDialog.finishPressed( 
   at org.eclipse.jface.wizard.WizardDialog.buttonPressed( 
   at org.eclipse.jface.dialogs.Dialog$2.widgetSelected( 
   at org.eclipse.swt.widgets.TypedListener.handleEvent( 
   at org.eclipse.swt.widgets.EventTable.sendEvent( Code)) 
   at org.eclipse.swt.widgets.Widget.sendEvent( 
   at org.eclipse.swt.widgets.Display.runDeferredEvents( 
   at org.eclipse.swt.widgets.Display.readAndDispatch( Code)) 
   at org.eclipse.jface.window.Window.runEventLoop( 
   at org.eclipse.swt.widgets.TypedListener.handleEvent( 
   at org.eclipse.swt.widgets.EventTable.sendEvent( Code)) 
   at org.eclipse.swt.widgets.Widget.sendEvent( 
   at org.eclipse.swt.widgets.Display.runDeferredEvents( 
   at org.eclipse.swt.widgets.Display.readAndDispatch( 
   at org.eclipse.ui.internal.Workbench.runEventLoop( 
   at org.eclipse.ui.internal.Workbench.runUI( 
   at org.eclipse.ui.internal.Workbench.createAndRunWorkbench( 
   at org.eclipse.ui.PlatformUI.createAndRunWorkbench( 
   at org.eclipse.core.internal.runtime.PlatformActivator$ 
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
   at sun.reflect.NativeMethodAccessorImpl.invoke( 
   at sun.reflect.NativeMethodAccessorImpl.invoke( 
   at sun.reflect.DelegatingMethodAccessorImpl.invoke( 
   at java.lang.reflect.Method.invoke( 
   at org.eclipse.core.launcher.Main.basicRun( 
   at org.eclipse.core.launcher.Main.main( 

The solution (for fixing code that makes excessive http requests)

While there is no one solution for all situations where you want to avoid or minimize network access, here we will mention a few things to consider.

  • Use an XML Catalog, with copies of resources on your local disk.
  • Set validation off, and set a null resolver.
  • Use a cache, so resources are at least only retrieved once, such as the cache in WTP!

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