webmacro-devel

[Webmacro-devel] Why can't webmacro.jar be replaced without restart?

[Marc P. <ma...@an...>]

Guys, I imagine a few of use are familiar with this message after trying to 
replace webmacro.jar and restarting/reloading the web application without 
restarting the servlet container:

WebMacro Error:

Could not initialize the broker!
*** Check that WebMacro.properties was in your servlet
*** classpath, in a similar place to webmacro.jar *** and that all values 
were set correctly.
IO Error reading WebMacro.defaults
java.io.FileNotFoundException: JAR entry WebMacro.defaults not found in 
E:\Program Files\Apache Group\Tomcat 4.1\webapps\ignition\WEB- 
INF\lib\webmacro.jar
Please contact the server administrator


Do we know why this is happening? It is hard to see how it can be a WM 
thing, as it looks more like a generic classloader issue.

However I think this is a pretty serious problem we need to address, 
because it is really bad news if you have to ask a network admin to restart 
a shared Tomcat instance, thus bringing down everybody else's sites.

It looks like the problem is occurring here in Settings:

    public void load (String fileName) throws InitException, IOException
    {
        ClassLoader cl = this.getClass().getClassLoader();
        URL u = (cl == null) ? null : cl.getResource(fileName);
        if (u == null)
            u = ClassLoader.getSystemResource(fileName);
        if (u == null)
            try
            {
                u = new URL("file:" + fileName);
            }
            catch (MalformedURLException e)
            {
            }
        ;

	....
    }

Now, as the webapp is being reloaded by the container, everything should be 
running on top of a new ClassLoader and therefore this probably should work 
fine.

Perhaps there is some strange issue here with servlet containers (this is 
seen in Tomcat 4.1.18, 4.1.24 and I think Eric said Resin 2.x too) that we 
could work around by using ServletContext.getResource in Settings?

This would mean refactoring Settings to pass in the URL instead of the 
filename, which could be a good thing - putting the responsibility of 
finding the file on the caller (Broker).

Anybody think they might know what's going on here?

Marc
-- 
Marc Palmer
Contract Java Consultant/Developer
			
                        w a n g j a m m e r s

                 java and web software design
              experts with an ethical outlook

                   http://www.wangjammers.org

Re: [Webmacro-devel] Why can't webmacro.jar be replaced without restart?

[Brian G. <br...@qu...>]

> Guys, I imagine a few of use are familiar with this message after trying to 
> replace webmacro.jar and restarting/reloading the web application without 
> restarting the servlet container:

Great question.  I think this is worth spending some effort on -- much
more worthwhile than debating about whether or not to kill Context
tools :)

Re: [Webmacro-devel] Why can't webmacro.jar be replaced without restart?

[Sebastian K. <seb...@mu...>]

Hi,

On Wednesday 23 July 2003 12:11, Marc Palmer wrote:
> Guys, I imagine a few of use are familiar with this message after trying to
> replace webmacro.jar and restarting/reloading the web application without
> restarting the servlet container:
>
> WebMacro Error:
>
> Could not initialize the broker!
> *** Check that WebMacro.properties was in your servlet
> *** classpath, in a similar place to webmacro.jar *** and that all values
> were set correctly.
> IO Error reading WebMacro.defaults
> java.io.FileNotFoundException: JAR entry WebMacro.defaults not found in
> E:\Program Files\Apache Group\Tomcat 4.1\webapps\ignition\WEB-
> INF\lib\webmacro.jar
> Please contact the server administrator
>
>
> Do we know why this is happening? It is hard to see how it can be a WM
> thing, as it looks more like a generic classloader issue.

I've tried to track this down the last two hours, but I have no clue. I did 
the following to get a minimal test case.

I modified Standalone.java from our examples slightly, so that it worked as 
expected:
- Passed a "this" reference in new WM()
- called super.init(sc) at the beginning of the overriden init method

I then created a simple web-app with the following files:
webapps/test/standalone.wm
webapps/WEB-INF/web.xml
webapps/WEB-INF/classes/Standalone.class
webapps/WEB-INF/lib/webmacro.jar

This works as expected. When I "touch" webmacro.jar the webapp gets reloaded 
and everything works as expected. However, when I change a core WebMacro 
class sligthly, so that the size of webmacro.jar changes and put this 
modified webmacro.jar in place, things fails after reloading the webapp.

However, I'm getting another message than Marc which really hints at a 
classloader issue:

avax.servlet.ServletException: Error instantiating servlet class Standalone
        at 
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:912)
        at 
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668)
        at 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at 
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at 
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:484)
----- Root Cause -----
java.lang.NoClassDefFoundError: org/webmacro/ContextException
        at java.lang.Class.newInstance0(Native Method)
        at java.lang.Class.newInstance(Class.java:237)
        at 
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:903)
        at 
org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:668)
        at 
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at 
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at 
org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at 
org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at 
org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at 
org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at 
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at 
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at 
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at 
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:484)

Notice the root cause: 
"java.lang.NoClassDefFoundError: org/webmacro/ContextException"

Needless to say, that I did not do anything to ContextException.

I have no idea what's going on here, or how to track this down.

This all happens under tomcat-4.1.24

Sebastian

-- 
Sebastian Kanthak
PGP/GnuPG: http://www.muehlheim.de/~skanthak/pgp.html

Re: [Webmacro-devel] Why can't webmacro.jar be replaced without restart?

[Marc P. <ma...@an...>]

On Thu, 24 Jul 2003 11:56:29 +0200, Sebastian Kanthak 
<seb...@mu...> wrote:

> I've tried to track this down the last two hours, but I have no clue. I 
> did the following to get a minimal test case.

Sebastian, thanks for spending some time on it!

The error you get is different probably just because I am based on 
WMServlet and you are based on Standalone.

This is very strange though, because we know for a fact that other JARs are 
reloaded fine in Tomcat and Resin.

So there must be something specific to webmacro.jar that is different. It 
does not look like some strange classloader usage issue -within- WM code 
though, which was possible with my flavour of the problem, because yours is 
a class loading (rather than resource) problem.

The "touch" working without problem sounds to me like there might be some 
intelligence going on in the classloader, or because no code has actually 
changed it continues to work with the previous code on the previous 
classloader perhaps.

This is all speculation but that's all we have right now!

I'll see if I can see anything in the way the jar is built. I know, I must 
be crazy... but maybe its a problem with reloading zipped JARs vs unzipped 
jars for example.

Marc
-- 
Marc Palmer
Contract Java Consultant/Developer
			
                        w a n g j a m m e r s

                 java and web software design
              experts with an ethical outlook

                   http://www.wangjammers.org