Thanks for explaining it some more for me. I sort of came into the
discussion late an just wanted to drop my 2 cents about turbine having some
work done on its caching system. Just like you state, we could use the
turbine caching when we need the features of an in memory cache. I was just
clarifing that we would not be stuck with just one memory cache singleton
per turbine instance and thoughts to allow multiple caches has been tossed
about for expanding the turbine caching framework.
I wasn't attempting to say that the global cache would replace any disk or
external resource cache. Just that we could use them in implementing our
services.
l8r,
jb
[SNIPPED]
>
> I insist that we are mixing discussions here.
>
> Turbine cache is a memory based one, where the user of the
> service puts an object and
> then retrieves it.
>
> We need more than that. Our JetspeedDiskCache retrieves a URL
> (taking care of
> different threads doing the same), copies it to local disk,
> and it COULD store it in
> memory additionally. It handles issues such as Character
> encoding, avoiding repeated
> accesses to external servers, ...
>
> The turbine cache has no support for retrieving urls or
> similar features.
>
> Our ExternalResourceManager (I have a name for it, I think
> JetspeedDiskCache is not
> good) is a service that:
>
> - fetches (and serializes network access to) external,
> url-based resources (rss
> channels, dtds, user psml, content channels, ...)
> - checks for expiration of the network content and refreshes
> it if needed
> - MAYBE stores these objects as a MRU Memory Cache.
>
> When we migrate it, it should be used for all URL based
> access to objects in the
> system. For instance, to recover a channel or a user psml.
> Maybe even a template.
> This way, the administrator will be able to specify at
> deployment the "location map"
> for a server to retrieve external resources.
>
> The service that does currently memory caching in Jetspeed is
> the MemoryStore, taken
> from Cocoon. This object can be substituted by either the
> Turbine GlobalCacheService
> or the Avalon similar component. But, even if you do that,
> you will still have the
> problem of handling the different urls as a singleton (i.e.
> avoid loading 500 times
> the netscape DTD on startup).
>
> Beware that if we cache external URLs in memory, we will have
> to handle, currently,
> above 2000 objects, with a typical size of aroud 4 KB (the
> feeds are about 2MB each).
> The cache size in my copy is 9,1 MBytes of xml files. Most of
> the objects are rarely
> used, just once in a while when getPortlet() causes
> expiration or the feeder is run.
>
> Also, beware that if different objects use different caches
> without a clear control
> point (ResourceManager module), there is a risk that there
> are tough programming
> errors, or else that we end up repeating code to avoid
> problems like having separate
> threads in a race condition for getting a resource and
> sending bursts of requests to
> our content management servers.
>
> >
> > jb
> >
> >
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