launchpad-dev team mailing list archive

[Guilherme Salgado <salgado@xxxxxxxxxxxxx>]

On Mon, 2010-01-11 at 15:32 -0500, Gary Poster wrote:
> On Jan 11, 2010, at 2:59 PM, Guilherme Salgado wrote:
> 
> > On Fri, 2010-01-08 at 09:27 -0200, Guilherme Salgado wrote:
> >> On Thu, 2010-01-07 at 15:43 -0500, Francis J. Lacoste wrote:
> >>> 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.
> > 
> > When I came up with the plan above I think I blindly assumed the next
> > time a request kicked in after a mode switch, it would re-connect to the
> > database, thus connecting to the appropriate one. That doesn't happen;
> > the connections to the database will be reused (and thus stay connected
> > to the DB that was appropriate when they were created) until they are
> > explicitly closed or left marked as dead.
> > 
> > I can't think of an easy way to close a connection at the beginning of a
> > request (as we don't want to switch modes mid-request) and only once for
> > each connection. Do you guys have any ideas?
> 
> Can we check to explicitly close connections at the end of a request?

(Just discussed this with Gary on IRC and...)
Ok, so the plan now is to, at the end of a request (or maybe at the
beginning?), compare the databases of all our connections against
dbconfig.main_master and if they differ we close them, forcing a reopen
which will then connect to the correct db.

> 
> > I'm starting to think it'd be better to have the switch require the
> > read-only.txt file be put in place plus the server restarted, and then
> > later we can work on making it work without a restart. But I wonder if
> > just replacing the config changes (currently needed to switch) with the
> > read-only.txt file is a significant win to the LOSAs?
> 
> I don't think it is.  Making a restart not required is the win we are after.
> 
> Gary


-- 
Guilherme Salgado <salgado@xxxxxxxxxxxxx>

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