Re: [thredds] WMS servers side image cache

Hi Jay,

The TDS does use ehcache in a number of ways. I believe mainly for
tracking collections of real-time updated files on disk. John can go
into the details if you're interested.

The TDS does not use the ncWMS data array caching code that Guan
mentions below. Most of the current TDS caching is at the dataset level
rather than at the level of the actual data.

Ethan

On 5/12/2011 12:41 PM, Jay Alder wrote:
> There is a ehcache.xml spring config file in WEB-INF which looks
> promising but I don't see anything about WMS in the cache documentation.
> 
> http://www.unidata.ucar.edu/projects/THREDDS/tech/reference/ThreddsConfigXMLFile.html#Cache_Locations
> 
> 
> My cache directories are essentially empty. Can someone confirm or deny
> thredds WMS is using or could use ehcache? It would be great if I could
> use ehcache to cache the data for my tiles (and have them persist) so I
> can change the image styling on the fly (best of both worlds).
> 
> 
> 
> On 05/12/2011 10:36 AM, Guan Wang wrote:
>> In the original ncWMS package, caching has been considered through
>> Ehcache.
>>
>> http://www.resc.rdg.ac.uk/trac/ncWMS/browser/trunk/src/java/uk/ac/rdg/resc/n
>>
>> cwms/cache/TileCache.java
>>
>> Not sure if this is still kept after the integration with THREDDS.
>>
>> Guan
>> -----Original Message-----
>> From: thredds-bounces@xxxxxxxxxxxxxxxx
>> [mailto:thredds-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Jay Alder
>> Sent: Thursday, May 12, 2011 1:09 PM
>> To: THREDDS Users
>> Subject: [thredds] WMS servers side image cache
>>
>> Hi, I'm playing around with using Thredds WMS using a tiling scheme
>> similar to google maps and I was wondering if there was a way (or
>> something that could be added in the future) to cache WMS maps from the
>> thredds servlet? Since I'm using tiles, the requests are identical. I
>> was thinking thredds would be able to hash (say md5) the request url and
>> write the image to temporary folder. On the second request thredds would
>> look in the cache based on the hash, and return the image if its there
>> otherwise generate a new image.  Thredds would likely need to wipe the
>> cache on a restart in case the data changed.
>>
>> Using IDL I wrote some code that downloaded all the tiles at all levels
>> for a particular dataset, but it took about 12 hours to run and
>> generated 400,000+ tiles for only one variable. If thredds cached images
>> it would be a more "on demand" approach rather than trying to pre
>> generate millions of tiles. In the tiled world, caching would say a lot
>> of server side processing (especially for high resolution datasets) and
>> speed up the user experience.
>>
>> -Jay Alder
>>
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