[VFS] Better way to scan for modifications

[dazz_x]

Hi all,

I didn't see any forum for VFS, so I post here since I use it with the MicroContainer.

My question is about the possibility to know if a VirtualFile or one of its children has been recently modified.

Context :
I work on a grid that executes jobs. Each job instance arriving at a node is of the same type and delegates execution to an engine whose implementation depends on some metadata hold by the instance. The grid node is started as a service by the microcontainer, but messaging between nodes is performed by the Grid. I would like to be able to put jars in a predefined directory that could serve as an implementation for the Engine interface in a hot manner (i want to be able to hot deploy some implementations). I tried to understand deeply MC deployment framework to achieve that, but i certainly misunderstood some concepts as I've come to think that it was mandatory for me to write my own deployers (and the way to effectively implement that is a bit blur to me, since some parts of docs are not written).

So, I have a periodic scanner that is meant to determine if a directory has appeared elsewhere and then trigger a loading of the classes included in it (as jar files).
In my scanning method, I wanted to do a snapshot of the current VirtualFile hierarchy in order to compare it to the future hierarchy (found by the next scan).
But I didn't see any way to "freeze" the VirtualFile hierarchy as the VirtualFiles are bound to the handler objects so I can't do a freeze copy (or immutable if you prefer) that I can store and compare later.
I saw the hasBeenModified() method of Virtual File, but the modification time is said to be initialized at Handler's instantiation, so when the file is first "discovered" by the VSF.

I hope you'll see my point and give advice to me

Cheers

dazz_x

PS : sorry for my poor english

[alesj]

Have a look at my demos, its bootstrap to be exact:
- http://anonsvn.jboss.org/repos/jbossas/projects/demos/microcontainer/trunk/
See HDScanner class, its usage of files Map.

A bit more complicated impl is here:
- http://anonsvn.jboss.org/repos/jbossas/trunk/system/src/main/org/jboss/system/server/profile/basic/MetaDataAwareProfile.java

HTH

And for any VFS or Deployers issues you might have,
this is the right forum. ;-)

[dazz_x]

Hi alesj,

Thanks for your response, which was helpul to me.

I finally handled this case in a satisfactory way.
So, when I add/remove/modify a file under my hierarchy, i get a log that says "this file have been added, removed, modified" under the TRACE log level.

A the same time I log, I fire an EngineDeployment event to alert registered listeners that an event has happened.

Unfortunately, that doesn't work... I give you my deployment file :

 <bean name="ClassLoaderManager" class="com.mycompany.classloaders.MasterClassLoader">
 <constructor factoryMethod="getInstance"/>
 </bean>

 <bean name="Scanner" class="com.mycompany.deployers.scanner.Scanner">
 <install method="addListener">
 <parameter>
 <inject bean="ClassLoaderManager"/>
 </parameter>
 </install>
 <constructor>
 <parameter>/home/user/test/</parameter>
 </constructor>
 </bean>

With this xml portion, I want to add my ClassLoaderManager as a listener (simple addition to a CopyOnWriteArrayList in Scanner)
But it isn't registered... I see an error in the deployment of ClassLoaderManager at startup that is

12:52:17,886 ERROR [AbstractKernelController] Error installing to Instantiated: name=ClassLoaderManager state=Described
org.jboss.joinpoint.spi.JoinpointException: Constructor not found com.mycompany.classloaders.MasterClassLoader[] in [ReflectConstructorInfoImpl@1b66b06{[ReflectClassInfoImpl@12c9557{name=java.lang.ClassLoader}]}, ReflectConstructorInfoImpl@9f0d{[ReflectClassInfoImpl@12c9557{name=java.lang.ClassLoader}, ReflectClassInfoImpl@ca3783{name=com.mycompany.classloaders.MasterClassLoader$1}]}]
 at org.jboss.joinpoint.plugins.Config.findConstructorInfo(Config.java:274)
 at org.jboss.kernel.plugins.config.Configurator.resolveConstructor(Configurator.java:289)
 at org.jboss.kernel.plugins.config.Configurator.findConstructor(Configurator.java:255)
 at org.jboss.kernel.plugins.config.Configurator.getConstructorJoinPoint(Configurator.java:198)
 at org.jboss.kernel.plugins.config.AbstractKernelConfigurator.getConstructorJoinPoint(AbstractKernelConfigurator.java:137)
 at org.jboss.kernel.plugins.dependency.InstantiateAction.installActionInternal(InstantiateAction.java:61)
 at org.jboss.kernel.plugins.dependency.InstallsAwareAction.installAction(InstallsAwareAction.java:54)
 at org.jboss.kernel.plugins.dependency.InstallsAwareAction.installAction(InstallsAwareAction.java:42)
 at org.jboss.dependency.plugins.action.SimpleControllerContextAction.simpleInstallAction(SimpleControllerContextAction.java:62)
 at org.jboss.dependency.plugins.action.AccessControllerContextAction.install(AccessControllerContextAction.java:71)
 at org.jboss.dependency.plugins.AbstractControllerContextActions.install(AbstractControllerContextActions.java:51)
 at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
 at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1598)
 at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
 at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1062)
 at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
 at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:774)
 at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:540)
 at org.jboss.kernel.plugins.deployment.AbstractKernelDeployer.deployBean(AbstractKernelDeployer.java:331)
 at org.jboss.kernel.plugins.deployment.AbstractKernelDeployer.deployBeans(AbstractKernelDeployer.java:309)
 at org.jboss.kernel.plugins.deployment.AbstractKernelDeployer.deploy(AbstractKernelDeployer.java:130)
 at org.jboss.kernel.plugins.deployment.BasicKernelDeployer.deploy(BasicKernelDeployer.java:76)
 at org.jboss.kernel.plugins.deployment.xml.BasicXMLDeployer.deploy(BasicXMLDeployer.java:88)
 at org.jboss.kernel.plugins.deployment.xml.BasicXMLDeployer.deploy(BasicXMLDeployer.java:158)

Here is the relevant part of the code for my MasterClassLoader class :

public class MasterClassLoader extends ClassLoader implements EngineDeploymentListener{

 /**
 * Application Logger
 */
 private static final Logger log = Logger.getLogger(MasterClassLoader.class);

 private Map<File, EngineClassLoader> engineClassLoaders = new HashMap<File, EngineClassLoader>();

 private MasterClassLoader(ClassLoader parent) {
 super(parent);
 }

 @Override
 public void onDeploymentEvent(EngineDeploymentEvent e) {
 log.info("[********] Deployment Event : " + e.getType().toString());
 }

 /**
 * Static initializer to ensure Singleton
 * @return single instance of MasterClassLoader
 */
 public static MasterClassLoader getInstance() {
 return MasterClassLoaderHolder.instance;
 }

 private static class MasterClassLoaderHolder {

 public static MasterClassLoader instance = new MasterClassLoader(ClassLoader.getSystemClassLoader());
 }
}

Why do you think my MasterClassLoader is not deployed ? My static factory method run well in standard call...

Thanks in advance

dazz_x

[dazz_x]

OK, I've been a bit fast to post ....

But it seems a bit weird for me...

So, I add a factoryClass="com.mycompany.classloaders.MasterClassLoader" attribute to the constructor tag...

I don't get this error anymore.
It seems a bit strange that if a factory class is not provided, the system does not use Object class as default factory...

Thanks for having read me...

[alesj]

Yeah, I thought that was the case.

Hmmm, but I remember we already did this.
I guess it got lost with xml + metadata transition to jbossxb.
I'll check.

[alesj]

"alesj" wrote:
I'll check.

http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4191929#4191929

[dazz_x]

well done,

that seems logical

thanks