[mapguide-users] Guestion about speedup mapguide, diferent domainname to mapagent.fcgi.

[Traian Stanev]

Yes, the problem of the tiles not necessarily being on the same machine as the web server is one of the limitations/assumptions that I had in mind also. But then I decided that this can be worked around by using a file system mount from the web server to the server where the tiles are. I've seen a similar thing done on Linux/Apache, not sure if Windows could handle such a setup.
 
 
 
Traian
 

	-----Original Message----- 
	From: mapguide-users-bounces at lists.osgeo.org on behalf of Paul Spencer 
	Sent: Wed 2/28/2007 8:00 PM 
	To: MapGuide Users Mail List 
	Cc: 
	Subject: Re: [mapguide-users] Guestion about speedup mapguide,diferent domainname to mapagent.fcgi.
	
	

	I'll weigh in here :)
	
	There was a recent thread on the ka-map list that is relevant to this 
	discussion.  The poster claimed (I didn't verify it, but it seems 
	correct) that tile sources in google maps all point to a variety of 
	server names like:
	
	m0.google.com
	m1.google.com
	m2.google.com
	m3.google.com
	
	and that each of these resolves to the same IP.  This is being done 
	to provide more simultaneous connections than a default configuration 
	of a browser would make - and it works very well.
	
	The poster also provided a patch for ka-Map that implemented a simple 
	round-robin server picker from an array of available servers for the 
	tile code.  He claimed substantial improvement in apparent tile 
	loading speed because more tiles loaded simultaneously.
	
	I am going to be implementing his patch in ka-Map (in a slightly 
	different way, but the same concept) because I need this for a 
	current client.  I can report back on our success.
	
	On a side note, OpenLayers already has the capability to specify an 
	array of servers as a tile source for a layer.
	
	Finally, we've been looking closely at optimizing kaMap performance 
	for our client.  Part of this has involved reorganizing how the tiles 
	are physically cached on disk to avoid problems with having too many 
	entries per directory.  The other part was using the web server 
	directly to serve tiles.  This means the client is aware of the 
	server cache structure and the cache is directly exposed through the 
	web server.  A 404 error handler is used to trigger tile generation 
	when the cache does not contain a particular set of tiles.
	
	Also, we switched from Apache to lighttpd as it is quite a bit faster 
	at serving files.  There are also other web servers that are faster 
	than Apache.
	
	One of the problems I see with MapGuide's tile caching mechanism is 
	that the tiles are not stored at the web tier, but rather at the 
	server.  This implies that you must invoke some process in addition 
	to the web server and wait for the transfer between the server and 
	the web tier, even if they are on the same machine.  This would be a 
	very difficult problem to solve in MapGuide, though, because the 
	architecture allows you to set up multiple web tiers and multiple 
	servers in the back end - I don't envy Bob this particular problem :)
	
	Cheers
	
	Paul
	
	On 28-Feb-07, at 6:52 PM, Jason Birch wrote:
	
	> Hi Trevor,
	>
	> There are two points here:
	>
	> - If the tiles were served directly from disk by apache (or IIS), you
	> will likely better performance than through the tileservice, primarily
	> because there will be less CPU overhead.  However, the recent changes
	> there (caching maps, etc).
	>
	> - From the client level, they only have two pipes to receive those 
	> tiles
	> through, so even if you're serving 100 tiles per second, the client is
	> only going to be able to download two at a time.  They have to pull 
	> down
	> all of the HTML and JS code through the same pipes, so initial load 
	> time
	> can be a killer at high resolution (more tiles to fill the screen).
	>
	> On a somewhat-related note, TileCache looks interesting:
	> http://labs.metacarta.com/wms-c/
	>
	> Jason
	>
	>
	> -----Original Message-----
	> From: Trevor Wekel
	> Subject: RE: [mapguide-users] Guestion about speedup mapguide,diferent
	> domainname to mapagent.fcgi.
	>
	> I don't know how much network latency and bandwidth affect tile 
	> serving
	> speeds.  However, I have had very good tile serving performance over a
	> LAN with recent builds of MapGuide.  I have seen tile serving  
	> speeds in
	> excess of 100 tiles per second over a gigabit ethernet link with 
	> current
	> hardware (Pentium D 820).
	>
	> It would also be worthwhile to monitor CPU usage on the server while
	> tiles are being served.  I suspect the bottleneck is CPU and not 
	> network
	> latency or bandwidth.
	> _______________________________________________
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	> mapguide-users at lists.osgeo.org
	> http://lists.osgeo.org/mailman/listinfo/mapguide-users
	
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	|Paul Spencer                          pspencer at dmsolutions.ca    |
	+-----------------------------------------------------------------+
	|Chief Technology Officer                                         |
	|DM Solutions Group Inc                http://www.dmsolutions.ca/ |
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