Re: Hot Standby and handling max_standby_delay

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Hot Standby and handling max_standby_delay
Date: 2010-01-18 06:28:13
Message-ID: 4B53FF7D.9040800@enterprisedb.com
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Simon Riggs wrote:
> On Sun, 2010-01-17 at 22:57 +0200, Heikki Linnakangas wrote:
>>> It would be good if there was a keepalive WAL record with a
>> timestamp on it generated every N seconds while in streaming mode.
>>
>> Yeah, that would help. In streaming replication we could also send
>> such timestamp as a separate message, not within WAL.
>
> Is that something you're working on?

No.

> Do we need a new record type for that, is there a handy record type to
> bounce from?

After starting streaming, slices of WAL are sent as CopyData messages.
The CopyData payload begins with an XLogRecPtr, followed by the WAL
data. That payload format needs to be extended with a 'message type'
field and a new message type for the timestamps need to be added.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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