[ka-Map-users] Mapserver Throtteling

[Andrew Hughes]

Hey Again,

I will most likely do this myself and attempt to contribute back, but 
first with the explaination.

It is nice to see that in KA-Map that a Lock file is written to prevent 
simultaneous identical* tile requests (*or same meta tile). The 
principal of a simple lock file could also be used to throttle 
concurrent non-unique tile requests. I have experienced problems 
(particularly cascading to another server) where flooding the server 
trashes the cache and the client experience because of excessive load. 
Throttling the mapserver access to say X many concurrent requests would 
ensure quality of service to at least some users and would protect the 
cache integrity. Users that find themselves on an overloaded server 
could be given a tile with a polite message (and the browser told not to 
cache the image).

I also modified the "tile.php" to be a "readonly" server that provides a 
polite message... something that was very easy. This is much the same as 
above (without the throttle).


Comments?