Re: [Demexp-dev] Does the server need to call the client?

[David MENTRE]

Hello Augustin,

Augustin <address@hidden> writes:

> The problem is that the web client cannot know of the activity going on 
> between the server and all the hard clients.
>
> I was thinking that the server could be set up to 'call' (via xml rpc) the 
> web 
> client, whenever another client is updating the data. This way the web client 
> knows it needs to update its own internal records. 

Currently, there is no API for the server to push information to clients.

> Now, I understand that this particular way of doing might be troublesome for 
> you (requires much more coding). 

Yes. :-)

> There is a probably much better way to do it, that would never require the 
> server to call the web client.

A RSS feed is also available (updated for each new question or
response). Its format is currently not very good and might need a rework
for easier parsing by clients.

> I can use Drupal to schedule some cron jobs, and call the server at regular 
> intervals: the method would be 
> "what-has-changed-since-last-time-i-called-you?".

There is such a call in current API : get_timestamps(). This call
returns a compressed array of timestamps, one for each question. I'll
look at ways to have this on the XML RPC side.

> I don't know how you store the data, server side, and how the hard clients 
> remain up to date, but I imagine you already use a similar system. 
> Certainly you have a last-updated timestamp for each question...

Exactly.

> The question really is: what procedure do you currently use to make sure that 
> the clients (hard clients or the web client) always have the most up to date 
> data.

Currently, the hard client is getting the latest timestamps each time it
starts. 

> I can tell you one thing, though: it would be too much resource intensive for 
> the web client to call the server at each page view!

Sure. A regular cron job each 15 or 20 minutes would be frequent enough.

Best wishes,
d.
-- 
GPG/PGP key: A3AD7A2A David MENTRE <address@hidden>
 5996 CC46 4612 9CA4 3562  D7AC 6C67 9E96 A3AD 7A2A