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From "Stefan Guggisberg" <stefan.guggisb...@gmail.com>
Subject Re: SimpleDBPersistenceManager file cache?
Date Fri, 20 Apr 2007 14:42:49 GMT
hi phillip,

On 4/20/07, Phillip Rhodes <spamsucks@rhoderunner.com> wrote:
> hi everyone,
> Sorry for the basic question...

no problem and not a basic question at all ;-)

> Because applications on multiple machines need to be able to grab jackrabbit stored content
from the repository, I am using the SimpleDBPersistenceManager, with externalBLOBs set to
false.  I realize that if I set externalBlobs to true, the blobs will be stored on the filesystem,
but this makes the content "sticky", that is, accessible by only the machine that has it on
the filesystem.
> My question is:  Do I need to implement my own file caching for my application?  For
example, if my application repeatedly retrieves a binary file from the jackrabbit repository,
does jackrabbit cache the retrieved binary file on the filesystem for subsequent requests,
or is each request cause the same blob to be read from the db?

it's the former. items read from the persistence layer are cached in
jackrabbit. this
includes binary properties (i.e. blob values). furthermore, blobs read
from a db are
internally spooled to a temp file. once the binary property associated
with that
blob/temp file is evicted from the cache, the temp file will be deleted.

therefore, repeatedly requesting the same binary property will in general not
cause the same blob to be read repeatedly from the db (assuming it is still
in the cache of course).


> No problem either way, I just need to know, since I have 20,000 users with each user
having their own collection of images on a very high traffic site.
> Thank you everyone for all your help.  It's been great.
> Phillip

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