Re: pg_receivexlog --status-interval add fsync feedback

On Wed, Oct 22, 2014 at 9:26 AM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
> We seem to be going in circles. You suggested having two options,
> --feedback, and --fsync, which is almost exactly what Furuya posted
> originally. I objected to that, because I think that user interface is too
> complicated. Instead, I suggested having just a single option called
> --synchronous, or even better, have no option at all and have the server
> tell the client if it's participating in synchronous replication, and have
> pg_receivexlog automatically fsync when it is, and not otherwise [1]. That
> way you don't need to expose any new options to the user. What did you think
> of that idea?

I think it's pretty weird to make the fsync behavior of the client is
controlled by the server.

I also don't think that fsync() on the client side is useless in
asynchronous replication. Yeah, it's true that there are no
*guarantees* with asynchronous replication, but the bound on how long
the data can take to get out to disk is a heck of a lot shorter if you
fsync frequently than if you don't. And on the flip side, that has a
performance impact.

So I actually think the design you proposed is not as good as what was
proposed by Furuya and Simon. But I don't feel incredibly strongly
about it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company