[ka-Map-users] Can someone answer this question please or tell mewho I should ask it to?

[Paul Spencer]

Samuel,

using the force option is BAD ;).  What happens here is that every  
tile request causes the 'metatile' to be redrawn, which is the entire  
basis for optimizing performance.  Essentially you have created the  
absolutely worst case performance you possibly can by doing this.

Without force, whenever kaMap requests a tile that is not in the  
cache, it will draw a large map image and slice it up into tiles.  In  
doing this, it 'locks' the tile and the other tiles that would be  
drawn at the same time.  This means all requests for the nearby tiles  
will block while the tiles are being rendered.

When you use force, it forces EVERY request to do the same thing.  So  
for 16 requests to the tiles that would normally be rendered by one  
blocking operation, each one blocks and forces the large map draw  
even though the new tiles have already been created.

This was the motivation behind the timestamp stuff that I added.  I  
haven't tried to look into why this isn't working for you yet.  I  
assume you are using the latest CVS version?

Cheers

Paul

On 28-Jul-06, at 8:01 PM, Samuel Doyle wrote:

> Hi,
> I played with the force option in tile.php which appeared to be  
> very resource intensive. I extended upon this by adding another  
> 'force_redraw' field in the metadata section for each layer of  
> interest in the map file. This resulted in the desired effect  
> however, it is still very resource intensive even if I'm requesting  
> just one layer. For every request my server ends up thrashing like  
> mad. Does anyone have any insight they could provide?
>
> Thanks, S.D.
>
> "Delfos, Jacob" <Jacob.Delfos at maunsell.com> wrote:
> Samuel,
>
> Have you checked whether the URL is actually different? Are you  
> saying it serves out the same tiles, despite the different  
> timestamp? Did you check whether any tiles actually get re-written?
> Have you tried playing with the "force" parameter of tile.php? If  
> this creates a new tile, it means the problem is it decides it  
> doesn't need to be re-created. If "force" doesn't work, it means it  
> isn't able to re-create the tiles.
> Is there a timestamp directory present?
>
> regards,
>
> Jacob
>
>
>
> From: Samuel Doyle [mailto:sdoyle_2 at yahoo.com]
> Sent: 28 July 2006 09:31
> To: Delfos, Jacob
> Subject: RE: [ka-Map-users] Can someone answer this question please  
> or tell mewho I should ask it to?
>
> Thanks for the repsonse.
>
> Yes I have included the redraw_interval and have tried the various  
> combinations even setting tile_source to nocache setting the  
> redraw_interval to be both greater then and    less then the  
> refresh_inteval even though it looks as if it should be less then  
> what you set for the refresh_interval. In the end In the end I  
> always end up needing to delete the tiles directory populated by  
> mapserver in order to get them regenerated again.
>
> "Delfos, Jacob" <Jacob.Delfos at maunsell.com> wrote:
> Samuel,
>
> Have you looked at the redraw_interval, described in init.php? That  
> appends a timestamp to the URL of the tile, to force redrawing of  
> the tiles. refresh-interval only does a re-request, returning a  
> cached tile.
>
> regards,
>
> Jacob
>
>
> From: ka-map-users-bounces at lists.maptools.org [mailto:ka-map-users- 
> bounces at lists.maptools.org] On Behalf Of Samuel Doyle
> Sent: 28 July 2006 07:33
> To: ka-map-users at lists.maptools.org
> Subject: [ka-Map-users] Can someone answer this question please or  
> tell mewho I should ask it to?
>
> Sorry but I haven't received any answers for the questions I have  
> posted here but this one is a bit important.
>
> After poking around and guessing at based on what I noticed in the  
> KaMap code I have place a refresh_interval value in a metadata  
> section within a layer in my map file. Now, I can see a periodic  
> update on the map but the problem is when I have modifed a dbf file  
> under mapserver those changes are not reflected. So the question  
> is, is there something I need to do special to get MapServer or  
> KaMap or whatever to detect an update done to a map so that it is  
> served properly?? These changes to the map files are being done  
> programatically and not by hand.
>
> Thanks, S.D.
>
>
> _______________________________________________
> ka-Map-users mailing list
> ka-Map-users at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/ka-map-users

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|Paul Spencer                           pspencer at dmsolutions.ca   |
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|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|
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