Re: Sync Rep for 2011CF1

On Wed, 2011-02-16 at 17:40 +0200, Heikki Linnakangas wrote:
> On 16.02.2011 17:36, Simon Riggs wrote:
> > On Tue, 2011-02-15 at 12:08 -0500, Robert Haas wrote:
> >> On Mon, Feb 14, 2011 at 12:25 AM, Fujii Masao<masao.fujii@gmail.com>  wrote:
> >>> On Fri, Feb 11, 2011 at 4:06 AM, Heikki Linnakangas
> >>> <heikki.linnakangas@enterprisedb.com>  wrote:
> >>>> I added a XLogWalRcvSendReply() call into XLogWalRcvFlush() so that it also
> >>>> sends a status update every time the WAL is flushed. If the walreceiver is
> >>>> busy receiving and flushing, that would happen once per WAL segment, which
> >>>> seems sensible.
> >>>
> >>> This change can make the callback function "WalRcvDie()" call ereport(ERROR)
> >>> via XLogWalRcvFlush(). This looks unsafe.
> >>
> >> Good catch.  Is the cleanest solution to pass a boolean parameter to
> >> XLogWalRcvFlush() indicating whether we're in the midst of dying?
> >
> > Surely if you do this then sync rep will fail to respond correctly if
> > WalReceiver dies.
> >
> > Why is it OK to write to disk, but not OK to reply?
> 
> Because the connection might be dead. A broken connection is a likely 
> cause of walreceiver death.

Would it not be possible to check that? 

-- Simon Riggs           http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services