Thank you! Does checking disk cache for presence of an element involve a disk I/O? Or the disk cache map (index) remains in memory at all times?
Thank you Val ----- Original Message ----- From: Aaron Smuts [asm...@yahoo.com] Sent: 01/12/2010 10:05 AM PST To: JCS Users List <jcs-users@jakarta.apache.org> Subject: Re: question on isSpool=true JCS will look for items in the various auxiliaries in configuration order. If you specify a remote cache in the list before a disk cache, then JCS will look in the remote cache before the disk cache. Before JCS looks in disk, lateral, or remote auxiliaries, it will first check the memory cache. So, in your case, if the item is not in memory JCS will look on disk. If it find the item it will retrieve it, put it to the memory cache (if the diskUsagePattern is not UPDATE and the memory size is not 0). After the put call, the item will be returned to the client. The put functions as any other. If the memory store is full, the least recently used item in memory (assuming that you are using the LRU memory cache) will be spooled to disk. Items are queued and asynchronously put to all auxiliaries. So, no you don't have to wait for the next item to be written to disk. You only have to wait for it to be queue. Aaron --- On Tue, 1/12/10, game...@nationwide.com <game...@nationwide.com> wrote: > From: game...@nationwide.com <game...@nationwide.com> > Subject: Re: question on isSpool=true > To: "JCS Users List" <jcs-users@jakarta.apache.org> > Date: Tuesday, January 12, 2010, 9:19 AM > thank you. > > What about part 3 of the question? About disk writing being > synchronous/blocking. > > Thanks > Val > > > ----- Original Message ----- > From: Aaron Smuts [asm...@yahoo.com] > Sent: 01/11/2010 07:01 PM PST > To: JCS Users List <jcs-users@jakarta.apache.org> > Subject: Re: question on isSpool=true > > > > The IsSpool, IsLateral, and IsRemote specify whether an > item will be allowed to go to a disk, lateral, or remote > auxiliary respectively. If there is no disk auxiliary > configured, for instance, the IsSpool value is > irrelevant. By default all three are true. If > you configure a disk auxiliary, and if IsSpool is true for > the item, it will be spooled to disk per the disk usage > pattern. > > The default disk usage pattern sends items to disk only > when the memory store is full. In contrast, the UPDATE > disk usage pattern will send all items to disk regardless of > whether or not there is room in memory. > > Your description is reversed. If you are using the > LRU memory cache and if you have a size limit on the memory > of 100, the 1st item will be sent to disk when the 101st is > added, assuming that they were never accessed. If the > 1st item was accessed after the 2nd was inserted or > accessed, then the 2nd will be spooled. The least > recently used item will be spooled. > > Aaron > > --- On Mon, 12/28/09, game...@nationwide.com > <game...@nationwide.com> > wrote: > > > From: game...@nationwide.com > <game...@nationwide.com> > > Subject: question on isSpool=true > > To: "JCS Users List" <jcs-users@jakarta.apache.org> > > Date: Monday, December 28, 2009, 8:46 AM > > Here is a typical cache region > > configuration for us: > > jcs.region.lookupCache=DC2 > > > jcs.region.lookupCache.cacheattributes=org.apache.jcs.engine.CompositeCacheAttributes > > jcs.region.lookupCache.cacheattributes.MaxObjects=100 > > > jcs.region.lookupCache.cacheattributes.MemoryCacheName=org.apache.jcs.engine.memory.lru.LRUMemoryCache > > > jcs.region.lookupCache.elementattributes=org.apache.jcs.engine.ElementAttributes > > > jcs.region.lookupCache.elementattributes.IsEternal=false > > > jcs.region.lookupCache.elementattributes.MaxLifeSeconds=500000 > > jcs.region.lookupCache.elementattributes.IdleTime=1 > > jcs.region.lookupCache.elementattributes.IsSpool=true > > > jcs.region.lookupCache.elementattributes.IsRemote=true > > > jcs.region.lookupCache.elementattributes.IsLateral=true > > > > 1. Can you confirm I am reading this correctly? > > a. Some cached data (anything over 100 objects but > within > > the > > MaxLifeSeconds) will spill to disk, due to IsSpool = > true > > b. Although IsRemote and IsLateral are both set to > true, it > > really does > > not mean that cache will be remote or synchronized > between > > multiple > > servers since none of these aspects are configured > > > > 2. Can you clarify the implications of cached data > > "spilling" over to > > disk? Once I have 101st object (in the example above) > that > > cache > > determines is going to be cached, does it mean > that, > > when I as a user of > > this cache region do "getElement(101)", the caching > > framework will: > > a. Determine that 101 is not in the cache > > b. Send 1 LRUed object out to the disk cache (spill > > "cached" data to disk) > > c. Cache in memory element 101 > > > > 3. If the above sequence of events is correct, can I > > presume that 2a, 2b, > > 2c will be executed synchronously (i.e. the call to > > getElement will be > > blocking until all a, b, and c operations are > complete)? > > asynchronously? > > Combination of thereof? > > > > Thank you > > Val > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: jcs-users-unsubscr...@jakarta.apache.org > For additional commands, e-mail: jcs-users-h...@jakarta.apache.org > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: jcs-users-unsubscr...@jakarta.apache.org > For additional commands, e-mail: jcs-users-h...@jakarta.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: jcs-users-unsubscr...@jakarta.apache.org For additional commands, e-mail: jcs-users-h...@jakarta.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: jcs-users-unsubscr...@jakarta.apache.org For additional commands, e-mail: jcs-users-h...@jakarta.apache.org
