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From "Simon Horton" <Simon.Hor...@uk.mizuho-sc.com>
Subject RE: Guaranteed persistence
Date Wed, 04 Aug 2010 10:23:15 GMT
Hi Tim,

Try setting your MaxPurgatorySize to 0 so there is no asynchronous
caching of data written to the disk cache, it will reduce your
performance but means your data goes straight to disk. 

jcs.auxiliary.DC.attributes.MaxPurgatorySize=0

Purgatory
Writing to the disk cache is asynchronous and made efficient by using a
memory staging area called purgatory. Retrievals check purgatory then
disk for an item. When items are sent to purgatory they are
simultaneously queued to be put to disk. If an item is retrieved from
purgatory it will no longer be written to disk, since the cache hub will
move it back to memory. Using purgatory insures that there is no wait
for disk writes, unecessary disk writes are avoided for borderline
items, and the items are always available



-----Original Message-----
From: Tim Stibbs [mailto:stripybadger@gmail.com] 
Sent: 04 August 2010 08:25
To: JCS Users List
Subject: Re: Guaranteed persistence

I am using CompositeCacheManager.getUnconfiguredInstance(); and
configuring
it programatically with the following properties:

jcs.default=DC
jcs.default.cacheattributes=org.apache.jcs.engine.CompositeCacheAttribut
es
jcs.default.cacheattributes.MaxObjects=0
jcs.default.cacheattributes.MemoryCacheName=org.apache.jcs.engine.memory
.lru.LRUMemoryCache
jcs.auxiliary.DC=org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheF
actory
jcs.auxiliary.DC.attributes=org.apache.jcs.auxiliary.disk.indexed.Indexe
dDiskCacheAttributes
jcs.auxiliary.DC.attributes.DiskPath=C:\path\etc
jcs.auxiliary.DC.attributes.MaxKeySize=1000
jcs.auxiliary.DC.attributes.OptimizeAtRemoveCount=1000

My main aims are:
- guaranteed persistence - once I've added it to the cache, even if the
application crashes, the key value pair will still be available when the
app
starts up again
- a non-infinite cache - I want the number of items in the cache to not
exceed order of 1000 to conserve disk space, though the exact number is
not
important.

Do these sound like something that is possible with JCS? I've looked
through
all the documentation and can't find anything along these lines.

Thanks,

Tim.

On 3 August 2010 20:17, Jorge Medina <cerebrotecnologico@gmail.com>
wrote:

> Look at :
> http://jakarta.apache.org/jcs/RegionProperties.html
> and
> http://jakarta.apache.org/jcs/IndexedDiskCacheProperties.html
>
> What are the properties of your disk cache ?
>
>
> On Mon, Aug 2, 2010 at 4:51 AM, Tim Stibbs <stripybadger@gmail.com>
wrote:
> > Hi,
> >
> > I am looking into using JCS as a disk-based key-value store, and it
seems
> to
> > work fine. However if the jvm is terminated, the .key file may not
get
> > written to, and although the .data file has my data in, when I
restart
> the
> > application it cannot access anything in the cache (presumably due
to the
> > .key file being empty).
> >
> > So, is there anyway to force the cache to immediately persist to
disk?
> > Having MaxObjects=0 on the memory cache seems to help, but still
doesn't
> > cause the .key file to be written.
> >
> > I also though I might be able to use ICacheEventLogger to see when
data
> has
> > actually been written to the disk store, but the logging stuff
doesn't
> seem
> > to be in the released version, although it is in the documentation?
> >
> > Does anyone know if it is even possible to do what I am trying to
do, or
> > have any suggestions?
> >
> > Thanks.
> >
>
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