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From Joshua Fuller <joshful...@gmail.com>
Subject Re: Limiting Disk Cache Size?
Date Wed, 21 Sep 2005 01:07:03 GMT
Thanks again for the quick replies and clarifications. I now understand that 
the file will not grow indefinitely as you have the "OptimizeAtRemoveCount" 
option - that makes me feel better - except that if you don't get a lot of 
removes for a while, the file could get quite large. Have you thought about 
adding something like "OptimizeAtRecycleSize"? I'm thinking about extending 
the existing classes to do something like this - if the number of items in 
the recycle are X then optimize. Any thoughts?

Thanks again,
Josh Fuller

On 9/20/05, Smuts, Aaron <Aaron.Smuts@travelocity.com> wrote:
> 
>  Max objects at the region level sets configures the memory manager.
> 
>  http://jakarta.apache.org/jcs/RegionProperties.html
> 
>  If you use the indexed disk cache, then the MaxKeySize setting on that 
> auxiliary, configures the number of disk indexes that the disk can have.
> 
>  http://jakarta.apache.org/jcs/IndexedDiskCacheProperties.html
> 
>  This configuration limits the memory cache to 10 and the disk cache to 
> 1000 keys:
> 
>  ##############################################################
> 
> ##### Default Region Configuration
> 
> jcs.default=DC
> 
> jcs.default.cacheattributes=org.apache.jcs.engine.CompositeCacheAttributes
> 
> jcs.default.cacheattributes.MaxObjects=10
> 
> jcs.default.cacheattributes.MemoryCacheName=org.apache.jcs.engine.memory.lru.LRUMemoryCache
> 
>  ##############################################################
> 
> ##### AUXILIARY CACHES
> 
> # Indexed Disk Cache
> 
> jcs.auxiliary.DC=org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheFactory
> 
> jcs.auxiliary.DC.attributes=org.apache.jcs.auxiliary.disk.indexed.IndexedDiskCacheAttributes
> 
> jcs.auxiliary.DC.attributes.DiskPath=target/test-sandbox/indexed-disk-cache
> 
> jcs.auxiliary.DC.attributes.MaxPurgatorySize=500
> 
> jcs.auxiliary.DC.attributes.MaxKeySize=1000
> 
> jcs.auxiliary.DC.attributes.MaxRecycleBinSize=300
> 
>      ------------------------------
>  
> *From:* Joshua Fuller [mailto:joshfuller@gmail.com] 
> *Sent:* Tuesday, September 20, 2005 3:16 PM
> *To:* Smuts, Aaron
> *Cc:* JCS Users List
> *Subject:* Re: Limiting Disk Cache Size?
>  
>  I'm sorry I seem so confused on this - but I think it must come from a 
> misunderstanding of how the disk cache is used in the first place. The site 
> says "When the memory cache exceeds its maximum size it tells the cache hub 
> that the item to be removed from memory should be spooled to disk." What is 
> the "maximum size" then that is being referred to? I was under the 
> impression it was the "jcs.default.cacheattributes.MaxObjects" value, but 
> that does not seem to make sense now either. Can you clarify what values do 
> what in regards to disk cache? If I want 10 items in memory, and 1000 items 
> on disk in my cache - how can I do that?
> 
> Thanks,
> Josh Fuller
>  
> On 9/20/05, *Smuts, Aaron* <Aaron.Smuts@travelocity.com> wrote:
>  
>    ------------------------------
>  
> *From:* Joshua Fuller [mailto:joshfuller@gmail.com] 
> *Sent:* Tuesday, September 20, 2005 12:40 PM
> *To:* Smuts, Aaron
> *Cc:* JCS Users List
> *Subject:* Re: Limiting Disk Cache Size?
>  
>  Thanks for your quick response and help. So would you recommend setting 
> up multiple disk cache, and using the MaxKeySize value to limit it? Or is 
> your last statement saying that the MaxKeySize will not actually limit the 
> size of objects on the disk anyway, but only the number of keys in memory? 
> 
>  The indexec disk cache is a memory index of items on disk. The keys and 
> the starting location of on disk for an item are stored in memory. The 
> maxkeysize on the disk cache limits the number of keys stored in the index. 
> This has nothing to do with the max size setting on the memory cache. 
> 
>  So to clarify, if I have a database of 100,000 records that are heavily 
> used - and I have a cache setup with a MaxKeySize of 1,000 - then there is 
> nothing preventing all 100,000 records from being spooled to disk as long as 
> they have yet to expire?
> 
>  Yes and no. All of them can get spooled, but only 1000 will be available. 
> 
> 
> 
> 
> A follow-up question to that would be - Does the memory shrinker thread 
> get used also to clean up the disk cache items that may have expired, or how 
> do they get cleaned out?
> 
> Nope. It is just a memory cache shrinker.
> 
>  They get cleaned out when remove is called. Remove is called when you 
> call remove or when you call get and an item is found to be expired.
>  
>  
> Thanks,
> Josh Fuller
>  
> On 9/20/05, *Smuts, Aaron* <Aaron.Smuts@travelocity.com> wrote:
> 
> You can only limit the number of keys, not the size of the file. The
> disk cache keeps track of empty spots from where an item has been
> removed and it tries to reuse them, but this doesn't stop it from
> growing indefinitely if you keep putting larger and larger items on 
> disk. I don't think that the disk cache marks a spot as available when
> a key is spooled off the disk cache key lru. . . .
> 
> > -----Original Message-----
> > From: Joshua Fuller [mailto: joshfuller@gmail.com]
> > Sent: Monday, September 19, 2005 9:07 PM
> > To: jcs-users@jakarta.apache.org
> > Subject: Fwd: Limiting Disk Cache Size?
> > 
> > Sorry, if this is a repeat - the last email didnt seem to send so I'm
> > trying
> > again......
> >
> > Is there a way to limit the size of the items in the cache being
> stored to
> > disk for a given region, or even globally? I can't find any setting 
> > anywhere
> > that limits the size of the files on disk (by number of elements or
> > physical).
> >
> > Thanks,
> > Josh Fuller
>  
>

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