module Eliom_cscache:sig
..end
Client-server cache for Eliom applications, that is used both for keeping data on client side or keeping values in memory during a request.
When you get a piece of data through Eliom_cscache from client-side, the request to the server is done only if the data is not already in the client-side cache.
On server side, Eliom_cscache is using a temporary cache (with "request" scope) to avoid fetching the data several time from the database during the same request. This server-side cache is automatically sent to the client to fill the client-side cache. If you want to avoid too many requests from the client, prefill the server-side cache with the data the client program will need.
This module hides many subtelties that are useful for client-server (possibly reactive) applications, like, for example, handling delays correctly both on client and server sides.
In the near future, Eliom_cscache will make it possible to save persistent data, which is useful for implementing off-line applications.
type ('a, 'b)
t
The type of association tables (implemented using Hashtbl)
val find : ('a, 'b) t -> ('a -> 'b Lwt.t) -> 'a -> 'b Lwt.t
find cache get_from_db key
returns the value associated to key
in cache. If not present, it calls get_from_db
to fetch the
data from the database. get_from_db
must be implemented both
server and client sides. Several simultaneous call to find
will
result in a single call to get_from_db
. Exceptions are not
cached.
val do_cache : ('a, 'b) t -> 'a -> 'b -> unit
do_cache cache key value
adds the association from key
to
value
in cache
, or replaces it if not already present. Called
from client side, it affects only client side cache. Called from
server side, it will have effect both on the server cache (scope:
request) and the client side cache.
val local_find : ('a, 'b) t -> 'a -> 'b Lwt.t
Find a piece of data in local cache, without trying to fetch it
from server. Raises Not_found
instead. If the value is currently
being retrieved, it waits for it to be ready before returning.
exception Not_ready
val find_if_ready : ('a, 'b) t -> 'a -> 'b
Find a piece of data in local cache, without trying to fetch it
from server. Raises Not_found
instead. If the value is currently
being retrieved, it raises Not_ready
.
Load (or reload) in cache the piece of data from server
val create : unit -> ('a, 'b) t
Create a new table. Must be called from server side.