[ka-Map-users] evaluating ka-Map

[Paul Spencer]

... exactly.  And as I mentioned, there is the possibility of client 
side caching so that the client may not get the latest version of the 
data OR they may get mis-matched data.

Not insolvable problems, but definitely working at the limits of what 
ka-Map was intended to do.

Cheers

Paul

David Bitner wrote:
> The issue isn't that grabbing the WMS would be all that much of a 
> performance hog, the issue is that ka-map relies on caching the tiles 
> that it uses.  You will not need to write the WMS to a static file, and 
> that really wouldn't help you at all.  For something like real-time 
> weather, you could set up a cron job that cleared the cache out every so 
> often, otherwise ka-map would be calling up the cache of old information 
> even when there is new information available.  Along with this, you 
> would have a performance hit because you would constantly be making 
> calls to mapserver and the WMS rather than just a call to a cached image.
> 
> David
> 
> On 9/9/05, *Nate Reed* <nate at seastar.jpl.nasa.gov 
> <mailto:nate at seastar.jpl.nasa.gov>> wrote:
> 
>     Good points, Charlton.  I can see we might need to setup a regular cron
>     job to grab recent images from our WMS and write them to a static file
>     which ka-Map can then consume, and we do need to a way to expire tiles.
>     Probably could just force the page to reload with some JavaScript or
>     META tags?...
> 
>     On Fri, 9 Sep 2005, Charlton Purvis wrote:
> 
>      > Hey, Nate and Paul:
>      >
>      > > Just so I understand, is this because of the cost of loading
>     all the tiles
>      > > when a layer is toggled on/off, or does it use some kind of
>     optimization
>      > > that depends on static files?
>      >
>      > Nate, I've been playing around w/ ka-map lately, and it really is
>     slick.
>      > Paul, please correct me if I'm wrong . . .
>      >
>      > If you're serving up a layer via ka-map that is really a WMS
>     layer from
>      > another box, I *think* that ka-map will make n-WMS queries where
>     n is the
>      > number of tiles in your given view.  In other words, I don't
>     *think* that it
>      > makes one WMS query and then divides that image up into
>     tiles.  If that is
>      > the case, then a dependence on a foreign WMS layer might be tricky
>      > performance-wise.
>      >
>      > The other question I have is:  Assuming that WMS is OK and that
>     what I
>      > assumed above is way off base, what happens if the WMS layer is
>     real time
>      > weather stuff like Nate is using?  Wouldn't it only query the WMS
>     once to
>      > create the tiles = no real time update w/o doing something fancy
>     on your end
>      > to either clear those from the cache on the hour or tag some kind of
>      > temporal index to each tile?
>      >
>      > Thanks, Paul, for such a dynamite product in such a short period
>     of time.
>      >
>      > Charlton
>      >
> 
>     --
>     Nate Reed
>     Physical Oceanography DAAC
>     Jet Propulsion Lab / Raytheon ITSS
>     (626)744-5528  nate at seastar.jpl.nasa.gov
>     <mailto:nate at seastar.jpl.nasa.gov>
> 
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> 
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|Paul Spencer                           pspencer at dmsolutions.ca   |
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|Applications & Software Development                              |
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