Barry Leslie wrote:
On 7/24/09 1:56 AM, "Paul McCullagh" <[email protected]> wrote:
On Jul 23, 2009, at 3:15 PM, Stewart Smith wrote:
On Tue, Jul 21, 2009 at 09:28:54PM -0700, MARK CALLAGHAN wrote:
How is the serial log to be kept in sync with a storage engine given
the Applier interface? MySQL uses two phase commit, but the Applier
interface has one method, ::apply(). In addition to methods for
performing 2PC, keeping a storage engine and the serial log in sync
requires additional methods for crash recovery to support commit or
rollback of transactions in state PREPARED in the storage engine
depending on the outcome recorded in the serial log.
The bit that keeps banging in my head in regards to this is storing it
in the same engine as part of the transaction and so avoiding 2pc.
We discussed this on Drizzle Day, and that was my recommendation.
This would mean, after a transaction has committed, the replication
system asks the engine for a "list of operations" that were performed
by the transaction.
For engines that have this information in their transaction log, it is
a relatively simple task.
So at the engine level there would be something like a 'get' and 'put' for
transactions so that on the Master server after a commit the 'get' method is
called and the data is sent to the slaves where they call the engines 'put'
method to apply the transaction?
Would it be possible to cut out the middle man here and have the server tell
the engine where it's slaves are and the engine can just send the committed
transactions directly to the slave engines? This would make it a lot easier
to stream the transactions.
Yes, this is certainly possible in a PBXT-specific replication
publisher/subscriber module. I'm in the process of creating the default
asynchronous publisher/subscriber module and we can use that as a model
for doing a PBXT-specific one that takes advantage of the efficiencies
you point out above.
Cheers!
jay
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