launchpad-dev team mailing list archive

["Francis J. Lacoste" <francis.lacoste@xxxxxxxxxxxxx>]

On January 7, 2010, Guilherme Salgado wrote:
> As I explained earlier, to make the read-only mode switching
> transparent, I turned the main_master/slave config variables into
> properties of DatabaseConfig, which return either rw_main_* or
> ro_main_*, depending on the mode we're on. 
> 
> After our discussion we decided to cache the mode in the request so that
> we only look for the file once for each request (and, more importantly,
> it doesn't change mid-request).  One small problem with that, though, is
> that DatabaseConfig.main_master is called in some contexts which don't
> have a request, so we need to cope with that.  It doesn't sound like a
> show-stopper to me, but I'd like to know what you think.
> 

What are those context? If there is no concurrent possibility, then it's not 
really an issue.

> Here's the utility we discussed, which deals with a missing request
> nicely: http://paste.ubuntu.com/353092/
> 

I wouldn't make the request part of the utility. I'd let the call site handle 
the request caching. The only responsibility of the utility is in monitoring 
and logging the read-only state change.



-- 
Francis J. Lacoste
francis.lacoste@xxxxxxxxxxxxx

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