Re: Simplify final sync in pg_rewind's target folder and add--no-sync

On 25/03/18 15:26, Michael Paquier wrote:
> Hi all,
> 
> While looking at pg_rewind code, I have been surprised to find that the
> final fsync done on the target's data folder is done using initdb -S via
> a system() call.  This is in my opinion overcomplicated because we have
> a dedicated API in fe_utils able to do a fsync on a data folder, called
> fsync_pgdata() that I have implemented when working on data durability
> for the other backup tools.  So I would like to simplify the code as
> attached.
> 
> One difference that this patch introduces is that a failed sync is not
> considered as a failure, still failures are reported to stderr.  This
> new behavior is actually more consistent with what happens in pg_dump
> and pg_basebackup.  And we have decided previously to do so, see here
> for more details on the discussion:
> https://www.postgresql.org/message-id/CAB7nPqQ_B0j3n1t%3D8c1ZLHXF1b8Tf4XsXoUC9bP9t5Hab--SMg%40mail.gmail.com
> 
> An extra thing I have noticed, which is I think an oversight, is that
> there is no --no-sync option in pg_rewind.  Like the other binaries,
> this is useful to reduce the I/O effort when running tests.

Yeah, let's be consistent with the other utilities, on both of those things.

> Both things are implemented as attached.  I am of course not pushing for
> integrating that patch in v11 even if it is straight-forward, so I'll
> park it in the next future commit fest.

Looks good to me. I'll mark this as "ready for committer".

- Heikki