>Date: Thu, 18 Oct 2007 02:36:28 -0400 >To: "Douglas Clark" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> >From: Stephen Bannasch <[EMAIL PROTECTED]> >Subject: RE: caching, now and in the future >Cc: [email protected], [EMAIL PROTECTED], [EMAIL PROTECTED] >(Bob Tinker), [EMAIL PROTECTED] >Bcc: >X-Attachments: > >At 6:51 PM -0700 10/17/07, Douglas Clark wrote: >>Hi Steve and Hiroki, >> >>Could you please explain to me the options/capabilities we have to >>cache files: >> >>a) locally on a server at a school >>b) locally on individual computers that students will use >> >>I am trying to figure out how to avoid/minimize bandwidth issues. > >I am cc'ing this to the SAIL dev list as well as a few folks at CC >who I think will be interested in the response. > >---- > >When a TELS SAIL project is first downloaded aprox. 20MB of Java >webstart jars are cached on the users file system. Normally this >file system is the local hard drive however a school could setup a >network drive as a user file system and then the webstart jars will >be cached there. > >Unless an administrator makes a change in the specification of what >jars are used for the Project these files will not be downloaded >again. If one jar out of a collection of 30 is updated then just >the changes in this jar will be downloaded. > >All these jars sit on a TELS server and are delivered by the Tomcat >Java web server running the Java webstart servlet. While the normal >delivery consists of only 20-30 MB the webstart servlet actually >stores versioned copies of all the jars back to October 2006. This >is so older projects can be run again using the same jars that the >students used. These older jars are not needed for any newer >deployments. The total of all the jars made available by the >webstart servlet is about 500 MB (maybe more now). > >We have not done much work to make this easy but it would certainly >be possible to setup a server in a school that could deliver these >jars on he schools local area network. > >SAIL/TELS activities consist of curnits (the project data, along >with html resources and assembly instructions for the project) and >external web resources that are downloaded during a project (movies, >flash, images). New curnits are created by authors and researchers >at infrequent intervals (1 week -- 3 months) however it would still >be a decision of some TELS admin in collaboration with the author >when to release this new curnit. > >While curnits are jar files they are not delivered by webstart and >are not cached with the other java webstart jars. Right now there is >no formal caching of curnits or external web resource. Many schools >have a caching proxy that these images and movies pass through. If >the resource is cachable then the proxy keeps a copy and the next >request from a computer on the local school network for that >resource is fufilled by the proxy without forwarding the request to >the original server. > >If we made a deployable server that replicated the java webstart >servlet then would not be a large amount of additional work to also >support delivering curnits and even external web resource from this >server also. > >I have designed and partially implemented the ability for the new >authoring system I am working on at CC to be replicated to the >school or any individual's computer and be able to sync the webstart >jars, curnits, and external web resources need for SAIL activities. >In addition the authoring, reporting, and deploying system itself >would be part of what is replicated locally. > >This work is on a back burner until I get the actual authoring >system much more advanced. The integration between authoring >deploying, reporting is quite complex even though the integration of >OTrunk into SAIL has made certain parts much easier. > >I expect the TELS Portal at some point to support a modular >architecture so the authoring and reporting tools we are developing >at CC and for the LOOPS project will be able to be integrated with >TELS where hey end up being useful. I'd like to make progress >towards that goal at he SAIL technical retreat. > >-- > >- Stephen Bannasch > Concord Consortium, http://www.concord.org
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