Re: pg_basebackup may fail to send feedbacks.

Sorry, I misunderstood that.

> > At Wed, 4 Feb 2015 19:22:39 +0900, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote in <CAHGQGwGudGCMnHZinkd37i+JijDkruEcrea1NCRs1MMtE3rOFQ(at)mail(dot)gmail(dot)com>
> >> On Wed, Feb 4, 2015 at 4:58 PM, Kyotaro HORIGUCHI
> >> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> >> > I'm very sorry for confused report. The problem found in 9.4.0
> >> > and the diagnosis was mistakenly done on master.
> >> >
> >> > 9.4.0 has no problem of feedback delay caused by slow xlog
> >> > receiving on pg_basebackup mentioned in the previous mail. But
> >> > the current master still has this problem.
> >>
> >> Seems walreceiver has the same problem. No?
> >
> > pg_receivexlog.c would have the same problem since it uses the
> > same function with pg_basebackup.c.
> >
> > The correspondent of HandleCopyStream in wansender is
> > WalReceiverMain, and it doesn't seem to have the same kind of
> > loop shown below. It seems to surely send feedback per one
> > record.
> >
> > | r = stream_reader();
> > | while (r > 0)
> > | {
> > | ... wal record processing stuff without sending feedback..
> > | r = stream_reader();
> > | }
>
> WalReceiverMain() has the similar code as follows.
>
> len = walrcv_receive(NAPTIME_PER_CYCLE, &buf);
> if (len != 0)
> {
> for (;;)
> {
> if (len > 0)
> {
> ....
> len = walrcv_receive(0, &buf);
> }
> }

The loop seems a bit different but eventually the same about this
discussion.

408> len = walrcv_receive(NAPTIME_PER_CYCLE, &buf);
409> if (len != 0)
410> {
415> for (;;)
416> {
417> if (len > 0)
418> {
425> XLogWalRcvProcessMsg(buf[0], &buf[1], len - 1);
426> }
427-438> else {break;}
439> len = walrcv_receive(0, &buf);
440> }
441> }

XLogWalRcvProcessMsg doesn't send feedback when processing
'w'=WAL record packet. So the same thing as pg_basebackup and
pg_receivexlog will occur on walsender.

Exiting the for(;;) loop by TimestampDifferenceExceeds just
before line 439 is an equivalent measure to I poposed for
receivelog.c, but calling XLogWalRcvSendHSFeedback(false) there
is seemingly simpler (but I feel a bit uncomfortable for the
latter)

Or other measures?

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center