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From Tim Stibbs <stripybad...@gmail.com>
Subject Re: Guaranteed persistence
Date Wed, 04 Aug 2010 12:20:51 GMT
Thanks for that Simon, I had missed the UsagePattern.

However, it doesn't seem to make any difference to the results.

MaxObjects=0 and MaxPurgatorySize=0 together seem to prevent anything going
into either memory or disk cache (so if I do a put, immediately followed by
a get on the same key I get back null). Remove either option and that
doesn't happen.

With either or both or neither of the options above, it all works if I
follow the puts with a small sleep - this would suggest that it is still
running asynchronously.

Thanks again,

Tim.

On 4 August 2010 12:09, Simon Horton <Simon.Horton@uk.mizuho-sc.com> wrote:

> 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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> TEL. 020 72361090. Wholly owned subsidiary of Mizuho Securities Co., Ltd.
> Member of Mizuho Financial Group. Authorised and regulated by the Financial
> Services Authority. Member of the London Stock Exchange.
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