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From "Javier Puerto (JIRA)" <>
Subject [jira] Updated: (DROIDS-68) HandlerFactory fails with multithreaded implementation
Date Wed, 09 Dec 2009 08:54:18 GMT


Javier Puerto updated DROIDS-68:

    Attachment: droidsTest_concurrency.patch

There is two files. The first one change the default implementation of the crawler and makes
it abstract. You must implement the method getWorker to detail the handlers that the worker
can use.

The HandlerFactory is now with the workers.

The another patch is a fix for the actual testcases and removing the indexer that was not

> HandlerFactory fails with multithreaded implementation
> ------------------------------------------------------
>                 Key: DROIDS-68
>                 URL:
>             Project: Droids
>          Issue Type: Bug
>          Components: core
>         Environment: Ubuntu 9.04 i386
> Java Runtime 1.6_16
>            Reporter: Javier Puerto
>            Priority: Critical
>         Attachments: droids_concurrency.patch, droidsTest_concurrency.patch
> Hi, I'm working with Droids and made some URL crawlers to save a lot of web pages in
disk. In JUnit test, I run a little http server and crawl 20 pages, the most times everything
works ok but in rare cases I get an error. I found the problem in the HandlerFactory implementation,
in the example the call to handlers is like this:
> protected void handle(ContentEntity entity, Link link)
>     throws DroidsException, IOException
> {
>   droid.getHandlerFactory().handle(link.getURI(), entity);
> }
> If two or more workers is trying to handle at same time, the HandlerFactory will handle
with the same instance. The solution could be saving memory or improving performance.
> The first solution could be implemented adding a "synchronized" to HandlerFactory.handle
like this.
> public synchronized boolean handle(URI uri, ContentEntity entity)
>     throws DroidsException, IOException {
>   for (Handler handler : getMap().values()) {
>     handler.handle(uri, entity);
>   }
>   return true;
> }
> This solution works but it is a workaround.
> The real solution was discussed in the dev list and it was make the Droid and the GenericFactory
abstractions clonable and invoking the clone method in the Worker's constructor.

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