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From "Simon Horton" <Simon.Hor...@uk.mizuho-sc.com>
Subject RE: Guaranteed persistence
Date Wed, 04 Aug 2010 11:09:19 GMT
Hi Tim,

I know you've set MaxObjects to zero so no items go to the memory cache,
but you may want to also set the DiskUsagePatternName to UPDATE in
conjunction with the MaxPurgatorySize setting from before?

jcs.default.cacheattributes.DiskUsagePatternName=UPDATE

The UPDATE usage pattern allows items to go to disk on an update. It
disables the swap. This allows you to persist all items to disk. 

http://jakarta.apache.org/jcs/RegionProperties.html



-----Original Message-----
From: Tim Stibbs [mailto:stripybadger@gmail.com] 
Sent: 04 August 2010 11:46
To: JCS Users List
Subject: Re: Guaranteed persistence

Thanks Simon,

That's one of the options I had tried - for some reason it seems to
result
in nothing being written to the cache at all. Is there another option
that I
need to use in conjunction with MaxPurgatorySize?

On 4 August 2010 11:23, Simon Horton <Simon.Horton@uk.mizuho-sc.com>
wrote:

> 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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any information contained herein. This message is not intended to create legal relations between
the company and the recipient. 
Recipients should please note that messages sent via the Internet may be intercepted and that
caution should therefore be exercised before dispatching to the company any confidential or
sensitive information. 
Mizuho International plc Bracken House, One Friday Street, London EC4M 9JA. TEL. 020 72361090.
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and regulated by the Financial Services Authority. Member of the London Stock Exchange. 

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