[mapserver-dev] RFC 110: Mapcache HTTP REST Cache backends

[Stephen Woodbridge]

On 4/18/2014 10:14 AM, thomas bonfort wrote:
> Hi devs,
>
> Please have a look at RFC110:
> http://www.mapserver.org/development/rfc/ms-rfc-110.html

The RFC and the feature look great. This will be a nice addition.

I'm just trying to get my head around how this works in practice. Is 
this just defining an alternate cache like a filesystem cache? So if I 
have say an openlayers layer that points to my mapcache instance and it 
is configured with a cloud cache, then when an incoming tile request is 
recieved mapcache does a HEAD or GET to check if the tile exists and 
sends it back if it does. otherwise it generated the tiles and PUTs then 
to the cloud and returns the requested tile in the process. In the case 
of a fully seeded cache, mapcache only needs to do 302 redirect to the 
tile in the cloud. Is this about right?

If mapcache maintained a meta-image of the cache where one bit/pixel 
equals a meta tile for each zoom level, you might be able to make a fast 
local check if you have sent the tile to the cloud and redirect based on 
that as performance optimization.

-Steve W