[jboss-dev-forums] [Design the new POJO MicroContainer] - VFS (URL) cache

[alesj]

I was looking into how to cache some things with VirtualFileURLConnection.
A simple initial attempt, to push things fwd:
 - http://anonsvn.jboss.org/repos/jbossas/projects/vfs/branches/cache-work/

What I tried to do is register every created VirtualFileHandler into cache - the key is VirtualFileHandler's vfs URL:

  |       if (vfsUrl != null)
  |          CacheLocator.getUrlCache().put(vfsUrl, this);
  | 

So when a VirtualFileURLConnection tries to access VirtualFile(Handler) we don't need to re-create the whole structure if it already exists.


  |    public static VirtualFileHandler resolveVirtualFileHandler(URL vfsurl, String relativePath) throws IOException
  |    {
  |       VFS vfs = VFS.getVFS(vfsurl);
  |       return vfs.findChild(relativePath).getHandler();
  |    }
  | 
  |    public synchronized VirtualFileHandler getVirtualFileHandler() throws IOException
  |    {
  |       if (handler == null)
  |       {
  |          boolean trace = log.isTraceEnabled();
  |          handler = CacheLocator.getUrlCache().get(vfsurl);
  |          if (handler == null)
  |          {
  |             handler = resolveVirtualFileHandler(vfsurl, relativePath);
  |             if (trace)
  |                log.trace("Resolving virtual file handler: " + vfsurl + "/" + relativePath);
  |          }
  |          else if (trace)
  |             log.trace("Handler resolved from cache: " + vfsurl + "/" + relativePath);
  |       }
  |       return handler;
  |    }
  | 
  |    public InputStream getInputStream() throws IOException
  |    {
  |       return getVirtualFileHandler().openStream();
  |    }
  | 

Since a AbstractVFSDeployment holds a strong ref to VirtualFile root, the whole structure should be there already (once touched), hence it should be possible to implement a simple cache with weak refs.
This didn't seam to be the case (or is it?), as weak refs were quickly gced - at least that's how it looked since no cache hits were present.
So and attempt was made with soft refs. :-)

This speeds up AS5 quite a bit, but I got a few failures. :-)

  | 2008-01-07 22:00:14,125 TRACE [org.jboss.virtual.plugins.vfs.VirtualFileURLConnection] Handler resolved from cache: vfsfile:/C:/projects/jboss5/trunk/build/output/jboss-5.0.0.Beta3/server/default/deploy/jboss-local-jdbc.rar/META-INF/ra.xml
  | 2008-01-07 22:00:14,140 DEBUG [org.jboss.resource.deployers.RARParserDeployer] Error during deploy: vfsfile:/C:/projects/jboss5/trunk/build/output/jboss-5.0.0.Beta3/server/default/deploy/jboss-local-jdbc.rar
  | org.jboss.deployers.spi.DeploymentException: Error parsing meta data jboss-local-jdbc.rar/META-INF/ra.xml
  | 	at org.jboss.deployers.spi.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:49)
  | 	at org.jboss.deployers.vfs.spi.deployer.ObjectModelFactoryDeployer.parse(ObjectModelFactoryDeployer.java:124)
  | 	at org.jboss.deployers.vfs.spi.deployer.AbstractVFSParsingDeployer.parse(AbstractVFSParsingDeployer.java:86)
  | 	at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:223)
  | 	at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:199)
  | 	at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.deploy(AbstractParsingDeployerWithOutput.java:162)
  | 	at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:169)
  | 	at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:853)
  | 	at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:794)
  | 	at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:327)
  | 	at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1309)
  | 	at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:734)
  | 	at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:862)
  | 	at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:784)
  | 	at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:622)
  | 	at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:411)
  | 	at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:498)
  | 	at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:506)
  | 	at org.jboss.system.server.profileservice.ProfileServiceBootstrap.loadProfile(ProfileServiceBootstrap.java:245)
  | 	at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(ProfileServiceBootstrap.java:131)
  | 	at org.jboss.bootstrap.AbstractServerImpl.start(AbstractServerImpl.java:408)
  | 	at org.jboss.Main.boot(Main.java:208)
  | 	at org.jboss.Main$1.run(Main.java:534)
  | 	at java.lang.Thread.run(Thread.java:595)
  | Caused by: org.jboss.xb.binding.JBossXBException: Failed to parse source: vfsfile:/C:/projects/jboss5/trunk/build/output/jboss-5.0.0.Beta3/server/default/deploy/jboss-local-jdbc.rar/META-INF/ra.xml at 1,1
  | 	at org.jboss.xb.binding.parser.sax.SaxJBossXBParser.parse(SaxJBossXBParser.java:177)
  | 	at org.jboss.xb.binding.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:186)
  | 	at org.jboss.deployers.vfs.spi.deployer.ObjectModelFactoryDeployer.parse(ObjectModelFactoryDeployer.java:120)
  | 	... 22 more
  | Caused by: org.xml.sax.SAXException: Content is not allowed in prolog. @ vfsfile:/C:/projects/jboss5/trunk/build/output/jboss-5.0.0.Beta3/server/default/deploy/jboss-local-jdbc.rar/META-INF/ra.xml[1,1]
  | 	at org.jboss.xb.binding.parser.sax.SaxJBossXBParser$MetaDataErrorHandler.fatalError(SaxJBossXBParser.java:438)
  | 	at org.apache.xerces.util.ErrorHandlerWrapper.fatalError(Unknown Source)
  | 	at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
  | 	at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
  | 	at org.apache.xerces.impl.XMLScanner.reportFatalError(Unknown Source)
  | 	at org.apache.xerces.impl.XMLDocumentScannerImpl$PrologDispatcher.dispatch(Unknown Source)
  | 	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
  | 	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  | 	at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  | 	at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
  | 	at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
  | 	at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
  | 	at org.jboss.xb.binding.parser.sax.SaxJBossXBParser.parse(SaxJBossXBParser.java:173)
  | 	... 24 more
  | 
And I don't see what exactly causes this.
The input stream for this should be from this piece of code - NoCopyNestedJarHandler:

  |    public InputStream openStream() throws IOException
  |    {
  |       return getJar().getInputStream(getEntry());
  |    }
  | 
Which should be there, even if cached.

Looking at the log, I do get a lot of cache hits, which somehow points to the right track.
Any thoughts or other ideas on how to cache VFS?


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