[Dbix-class] RFC: DBIx::Class::Storage::DBI::mysql_repl - replicated MySQL data source

[Norbert CSONGRADI]

On Tuesday 05 September 2006 10:54, Lee Standen wrote:
> How does it handle replication lag?

Currently no handling at all in this module.

> I don't know if this happens in MySQL, but with DB2 replication, there
> is the potential for data being read to be 15 or more minutes out of
> sync with the "real" data on the master database.  If this happens on
> MySQL as well, then there would be a necessity to query the row(s) you
> plan to update from the master database first, and then throw an
> exception if the data is different.

With our setup, it depends on the speed of the link between the master and 
slaves. MySQL handles replication very well, data is replicated in a fraction 
of a second if the link is fast enough.
The only problem we encountered so far if large amount of data is changed, 
replication could slow down to 1 second and it could cause problems. Our 
current fix for that if you expect a read operation right after your write 
operation, you can set the database handle to "urgent" mode, which require 
the next selects to go to the master database directly. Maybe I can integrate 
this fix into this implementation.

I go and refactor all the thinggy with DBD::Multiplex and post the result 
again in a couple of days anyway. mst++

-- 
Best regards,
   Norbert Csongradi