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 <[email protected]>
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