Re: [SQLObject] load balancing and SQLObject cache

[Егор С. <eg...@co...>]

It does not seem to work. When I set cache to 0 and debug to 1 in uri

DB URI ('postgres://host/db?cache=0&debug=1')

f = db.Person.get(5)
print f.name
f1 = db.Person.get(5)
print f1.name

I don't see second select to the database on second get.
Apparently, the value is fetched from expiredCache.

Any suggestions?

Thank you.

On 7/19/2011 7:34 AM, Oleg Broytman wrote:
> On Tue, Jul 19, 2011 at 12:21:32AM -0300, Егор Следов wrote:
>> I have a web application with two load-balanced webservers and a separate postgres database server.
>> 
>> When SQLObject instance is updated, the update is processed randomly through either of the servers. 
>> Sometimes user does the update on one server, and immediately opens object for reading on another. 
>> So, if caching is on, it looks like database is not getting updated.
>> 
>> If I turn caching off by setting sqlmeta.cacheValues to False, then call to each and every property issues a separate SQL select, and this slows everything down a lot.
>> 
>> What would be the right approach to minimize number of selects on a single webpage? 
>> Keeping cache on, but calling object.expire(), object.another.expire() after referencing any properties? Trying to lower cullFrequency parameter of cache?
> 
>    In SQLObject there are three ways of caching - attribute caching
> (governed by sqlmeta.cacheValues), row caching (governed by
> connection.cache), and update caching (governed by sqlmeta.lazyUpdates).
> What you probably want is to stop row caching - every time the programs
> fetches a row it asks the database, not the cache. So leave
> sqlmeta.cacheValues and sqlmeta.lazyUpdates alone (their default values
> are good for you) and set connection.cache.doCache=False. You can do it
> from DB URI ('postgres://host/db?cache=0'); if the program opens
> connection without an URI the parameter for PostgresConnection is
> cache=False.
> 
> Oleg.