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Date: Sun, 16 Aug 2009 14:01:42 -0400
Message-ID: <330f74e70908161101s4c38e4ehc3bab0e1f4574a08@mail.gmail.com>
Subject: Re: Okay next tqo quick questions...
From: Jeffrey Kesselman <jeffpk@gmail.com>
To: JCS Users List <jcs-users@jakarta.apache.org>
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Hi Aaron.

Thanks again for the help.

This is the issue. let me spell out my design and maybe you can either
correct it or suggest how to accompish it.

I have resource-masters that store and server the actual resources and
resource-clients that get from the master and use them.  The reource-clients
cache locally to disk.  These cached values should stay until they are
outdated by new versions of the same asset as asset download is expensive.

Client usage of resources is base on instructiosn sent  by the server,.
Because I want to scale out massively for the clients, I ama voiding having
the clients listen to puts of new resource versions.  Instead, when the
server instructs the client o use an asset it oncludes a version number. If
that version is not the one in teh cache, then the update is fecthed.  Im
simualtign version numbers using JCS by coding the version number into the
key-string.

Its worth notign this design ALSO nicely handles the issue of a client beign
offlien whern an updated resoruce is pushed into the master.  Next time it
is instructed to use it, it will go fecth it.

The issue is this:  Once I have a new version of an asset, I want to clear
the old version OUT of the client disk cache.  It is garbage and  no lonegr
needed and, over-time, this garbage coudl be quite significant in size.

The question is... how to garbage colelct the cache?  If I know when a new
version is beignf etched, I can synthetically create the names of odler
versions and make sure theya re deleted.  This was my first thought and the
genesis of my question about checkling to see if something is in the cache
before it is fecthed.

ANOTHER approach would be to walk through all the current locally stored
cache keys and delete any entreis for which there ar mroe recent versions.
(Again, i can determine this through the key-name conventions.)  Is this
dioable?

On Sun, Aug 16, 2009 at 10:23 AM, Aaron Smuts <asmuts@yahoo.com> wrote:

>
>
> --- On Fri, 8/14/09, Jeffrey Kesselman <jeffpk@gmail.com> wrote:
>
> > From: Jeffrey Kesselman <jeffpk@gmail.com>
> > Subject: Okay next tqo quick questions...
> > To: "JCS Users List" <jcs-users@jakarta.apache.org>
> > Date: Friday, August 14, 2009, 3:55 PM
> > (1)  Why does CacheAccess.get()
> > return an Object and not a Serializable.
> > Doesn't any object stored in the cache have to be a
> > Serializable?
> >
>
> The original ICacheAccess interface take and returns objects.  The idea was
> that the cache should be usable with just memory auxiliaries.  So we
> shouldn't restrict to Serializable.  However, nearly every other auxiliary
> requires it.  . .  .
>
> > (2) If i call get(...) on my remote cache and the object
> > isnt there, it will
> > attempt to fetch iot from its server yes?  is there
> > some way for me to know
> > this is happening? some kind of .contains(...) call I could
> > call first or
> > something?
> >
>
> You call get on a local cache.  It it is not present locally, the remote
> cache client will call get on the remote cache server.  If the server
> doesn't have it, it will do the same thing.  If the server is configured
> with a failover, it will call get on the failover.
>
> You don't have anyway to know before calling get what will happen
> underneath.  What would the contains method do?  I don't understand.
>
> Aaron
>
> > --
> > ~~ Microsoft help desk says: reply hazy, ask again later.
> > ~~
> >
>
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