On 10/08/2010 09:56 AM, Heikki Linnakangas wrote:
> Imagine a web application that's mostly read-only, but a
> user can modify his own personal details like name and address, for
> example. Imagine that the user changes his street address and clicks
> 'save', causing an UPDATE, and the next query fetches that information
> again to display to the user.
I don't think that use case justifies sync replication and the
additional network overhead that brings. Latency is low in that case,
okay, but so is the lag for async replication.
Why not tell the load balancer to read from the master for n seconds
after the last write. After that, it should be save to query standbies,
again.
If the load on the master is the problem, and you want to reduce that by
moving the read-only transactions to the slave, sync replication pretty
certainly won't help you, either, because it actually *increases*
concurrency (by increased commit latency).
Regards
Markus Wanner
