old web2py blog

CACHE QUOTA

This recipe is about web2py using RAM MEMORY for "disk caching" on linux(with TMPFS).

Ok, to the point:

You have to be logged in as root. Then you type:

mount -t tmpfs tmpfs $folder_path -o rw,size=$size

where:

$folder_path is a path to the folder where you mount your slice of RAM

$size is the amount of memory you want to dedicate( M - megabytes )

for example:

# # # #

mkdir /var/tmp/myquery
mount -t tmpfs tmpfs /var/tmp/myquery -o rw,size=200M

# # # #

You have just allocated 200M of your RAM. Now we have to map it in web2py application.

Since 03-11-2010 all of this is even easier an better, you just write in your models:

from gluon.cache import CacheOnDisk
cache.disk = CacheOnDisk(folder='/the/memory/mapped/folder')

so in our case:

cache.disk = CacheOnDisk(folder='/var/tmp/myquery')

and than:

db(...).select(cache=(cache.disk,3600)....)

or:

@cache(request.env.path_info, time_expire=5, cache_model=cache.disk)
def cache_controller_on_disk():
    import time
    t = time.ctime()
    return dict(time=t, link=A('click to reload',
                          _href=request.url))

[ controller example comes from the web2py book ]

this way you can have "ram space quota" for every query/controller/etc cached, and each one can have different size setting.