Re: Keepalive for max_standby_delay

On Mon, May 17, 2010 at 1:11 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Sat, 2010-05-15 at 19:50 +0100, Simon Riggs wrote:
>> On Sat, 2010-05-15 at 18:24 +0100, Simon Riggs wrote:
>>
>> > I will recode using that concept.
>
>> Startup gets new pointer when it runs out of data to replay. That might
>> or might not include an updated keepalive timestamp, since there's no
>> exact relationship between chunks sent and chunks received. Startup
>> might ask for a new chunk when half a chunk has been received, or when
>> multiple chunks have been received.
>
> New version, with some other cleanup of wait processing.
>
> New logic is that when Startup asks for next applychunk of WAL it saves
> the lastChunkTimestamp. That is then the base time used by
> WaitExceedsMaxStandbyDelay(), except when latestXLogTime is later.
> Since multiple receivechunks can arrive from primary before Startup asks
> for next applychunk we use the oldest receivechunk timestamp, not the
> latest. Doing it this way means the lastChunkTimestamp doesn't change
> when new keepalives arrive, so we have a stable and reasonably accurate
> recordSendTimestamp for each WAL record.
>
> The keepalive is sent as the first part of a new message, if any. So
> partial chunks of data always have an accurate timestamp, even if that
> is slightly older as a result. Doesn't make much difference except with
> very large chunks.
>
> I think that addresses the points raised on this thread and others.

Is it OK that this keepalive message cannot be used by HS in file-based
log-shipping? Even in SR, the startup process cannot use the keepalive
until walreceiver has been started up.

WalSndKeepAlive() always calls initStringInfo(), which seems to cause
memory-leak.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center