Re: pg_basebackup may fail to send feedbacks.

On Thu, Feb 5, 2015 at 10:20 AM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Hello,
>
> 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);
}
}

Regards,

--
Fujii Masao