Ruby on Rails

On Nov 30, 6:58 pm, Rafe Rosen <rafe.ro...@commonmediainc.com> wrote:
> I need to implement a feature for a rails site that will involve
> reading and exporting most of my database.
>
> I know this operation is going to take a while. That's fine-- I've got
> delayed job for that.
>
> What I'm worried about is the data changing during the running of the
> job, and the resulting export being corrupted because of that.
>
> My initial thought was to do all of the reads within a transaction.
> However, I would also like to be running the reads concurrently.
> ActiveRecord docs say that Transactions cannot be shared between
> Connections, and Connections cannot be shared between Threads. So it
> looks as though I am restricted to a single thread with this approach.
>
> Any suggestions for a workaround? Is there another way to give the job
> a consistent view of the data that doesn't involve transactions? Or is
> there some alternative to ActiveRecord/Mysql out there that can
> distribute transactions across threads?

One possibility would be to have a slave replicating from the master.
You can halt replication, do all your data dumping from the slave and
then resume replicating. This might also be a good idea because it
would mean that your export stuff wouldn't be impacting the main stuff
your site does.

Fred

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