> I am not very good at explaining these things. :-)
Not true. I've never been sure about how the DiskCache was meant to work,
and now I think I understand better, thanks to you.
I've been using the disk cache to resolve local, relative urls, and perhaps
I shouldn't be.
For ex.
url = JetspeedDiskCache.getInstance().getEntry(url).getURL();
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Santiago Gala
> Sent: Wednesday, January 10, 2001 12:50 AM
> To: JetSpeed
> Subject: Re: XSLPortlet , JetspeedContent
>
>
> David Sean Taylor escribió:
>
> > Thanks Santiago, I believe the Observer pattern to be a good choice.
> >
> > The old system never really worked for me, there's either a bug
> in expire()
> > or its too complicated for my feeble mind...
> > Anyway, Im very glad to hear you are working on a new impl.
> >
> > Im now discussing how the new system will work, please excuse
> me if Im being
> > redundant, but I really want to understand how this works!
> >
> > How will the cache determine when a file is modified on the file system?
>
> The DiskCache is NOT for caching local files, but for caching
> external URLs.
> One of the main problems that we faced is that it is difficult to know the
> difference. Currently, everthing local is served "as is" i.e. as
> a url, while
> every resource coming from a different server is cached in the
> WEB-INF/cache
> subdirectory.
>
>
> >
> > Will it run a daemon, which will periodically poll the file
> system and check
> > the modified date?
>
> The Disk Cache has a Daemon, that runs every so and so, and checks the
> lastModified and Expires fields of each URL. If the URL was
> modified, it is
> reloaded and all portlets depending on this url are expired (at
> least it was
> like this)
>
>
> >
> > Or is this controlled by the expire method() - is the expire
> method used to
> > set the polling frequency?
> > Alternatively, I assume this can be done by someone 'deploying'
> an updated
> > file, and then calling the refresh() method
>
> The DiskCache does not handle files.
>
> >
> > > You should think of the disk cache as URLManager, or
> ResourceManager. It
> > > is on
> > > charge of synchronising fetching and caching of external
> resources, more
> > > or
> > > less like what a HTTP proxy would do.
> >
> > when you say caching, where is the caching occurring? Is the
> DiskCache also
> > for resources on other html servers?
> > I thought it was only for local files. If its for local files,
> what exactly
> > is being cached if it doesn't use a memory cache?
> >
> > > The portlet used a memory cache, so your portlet should be cached in
> > > memory,
> > > until it expires. Once it expires, it will be reinstantiated. Look at
> > > the
> > > code in PortletFactory.
> >
>
> The memory cache is a different one. It is used to cache objects
> in memory. It
> is governed by an expiration mechanism. Portlets use this kind of
> memory cache
> to avoid recomputing them, while the remote rss url that defines
> RSSPortlets is
> stored by the disk cache to avoid going to the network every time..
>
> >
> > yes, i need to look at this.
> > Im not quite sure of the purpose of expiring portlets
>
> It is so that the items in the portlets can be recalculated from
> the url. If
> the url was refreshed by the DiskCacheDaemon in the while, the
> portlet will
> have new content. If not, it will simply be recalculated.
>
> I am not very good at explaining these things. :-)
>
> >
> >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED]
> > > [mailto:[EMAIL PROTECTED]]On Behalf Of Santiago Gala
> > > Sent: Tuesday, January 09, 2001 5:55 PM
> > > To: JetSpeed
> > > Subject: RE: XSLPortlet , JetspeedContent
> > >
> > >
> > > David Sean Taylor escribió:
> > >
> > >
> > > I'll send it CC to the list, with the old subject, so that
> the answer is
> > > public and other people can contribute.
> > >
> > > > Hi Santiago,
> > > >
> > > > I think you may have missed my email yesterday on the mailing
> > > list, so Im
> > > > including it again below.
> > > > Hope you don't mind me asking you directly, but I often do
> not receive
> > > > responses to threads that I start on the mailing list, for what
> > > reasons I
> > > > really dont know.
> > > >
> > >
> > > I was waiting until now, that I'm back in the office, to answer. This
> > > time I
> > > even flagged it to make sure I would remember,
> > >
> > > >
> > > > On a more serious subject :), I believe that you and I have
> broken the
> > > > build.
> > > > On your part, NewRSSPortlet uses the
> JetspeedXMLReaderFactory, which was
> > > > deleted.
> > > >
> > >
> > > It seems that I forgot to commit this one. I have just done it. Sorry
> > > aboutthat one :-(
> > >
> > >
> > >
> > > >
> > > > Here is the email from yesterday:
> > > >
> > > > "
> > > > Santiago, could you help me in understanding how the
> DiskCache works?
> > > > What I'd like to do is cache content in memory, but when
> the resource
> > > > changes on the disk, then refresh it.
> > >
> > > With the old cache, entries are checked only when the DiskCacheDaemon
> > > runs.
> > > The method "hasExpired" for a cache entry tells wether it has expired,
> > > and
> > > something like:
> > >
> > > URLFetcher.refresh( url ) should try to refresh (in the same thread)
> > > and
> > > return true, if it got refreshed, or false, if either it was
> not expired
> > > or
> > > there was some problem, or it was not modified in the server.
> > >
> > > The whole interface is changing. For the new version, I am
> implementing
> > > the
> > > cache entries as java.util.Observable, so that any object can declare
> > > itself
> > > as an observer of the entry, and be notified either when it expires or
> > > when it
> > > gets refreshed. Also, the entries will have a refresh method that will
> > > handle
> > > the refresh, if needed.
> > >
> > > I'm using Observable for tests, but we can change this class by some
> > > other
> > > interface if needed after the concept is tested. I will look
> for similar
> > > patterns in Turbine/Avalon code.
> > >
> > > >
> > > > Like the XSLPortlet. To optimize its performance it shouldn't
> > > have to run
> > > > the transform everytime.
> > > > Is caching content something that the DiskCache should be
> providing, or
> > > > should we be writing that code in our portlets (like the
> XSLPortlet)?
> > > >
> > > > Or for a simple html file. Is the DiskCache supposed to cache
> > > the file in
> > > > memory, and then figure out when its been modified and keep the
> > > memory copy
> > > > sychronized?
> > >
> > > The actual disk cache does not handle caching in memory. For what you
> > > want, we
> > > should probably have a "glue" object that contains the object, caches
> > > itself
> > > in memory using the memory cache, and takes care of the
> interaction with
> > > the
> > > disk cache.
> > >
> > > The portlet used a memory cache, so your portlet should be cached in
> > > memory,
> > > until it expires. Once it expires, it will be reinstantiated. Look at
> > > the
> > > code in PortletFactory.
> > >
> > > You should think of the disk cache as URLManager, or
> ResourceManager. It
> > > is on
> > > charge of synchronising fetching and caching of external
> resources, more
> > > or
> > > less like what a HTTP proxy would do.
> > >
> > > I think that the portlet expiration mechanism has some flaws, and
> > > possibly
> > > also the Disk Cache.
> > >
> > > I don't look at it very much, since the code is very messy and I'm
> > > working in
> > > a replacement. It has to be ready "real soon now". :-)
> > >
> > > >
> > > > "
> > > >
> > > > Thanks,
> > > >
> > > > David
> > >
> > >
> > > --
> > > --------------------------------------------------------------
> > > To subscribe: [EMAIL PROTECTED]
> > > To unsubscribe: [EMAIL PROTECTED]
> > > Search: <http://www.mail-archive.com/[email protected]/>
> > > List Help?: [EMAIL PROTECTED]
> > >
> > >
> >
> > --
> > --------------------------------------------------------------
> > To subscribe: [EMAIL PROTECTED]
> > To unsubscribe: [EMAIL PROTECTED]
> > Search: <http://www.mail-archive.com/[email protected]/>
> > List Help?: [EMAIL PROTECTED]
>
>
>
> --
> --------------------------------------------------------------
> To subscribe: [EMAIL PROTECTED]
> To unsubscribe: [EMAIL PROTECTED]
> Search: <http://www.mail-archive.com/[email protected]/>
> List Help?: [EMAIL PROTECTED]
>
>
--
--------------------------------------------------------------
To subscribe: [EMAIL PROTECTED]
To unsubscribe: [EMAIL PROTECTED]
Search: <http://www.mail-archive.com/[email protected]/>
List Help?: [EMAIL PROTECTED]
