From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <gsstark@mit.edu>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: time-delayed standbys
Date: Wed, 20 Apr 2011 10:19:35 -0400
Message-ID: <26007.1303309175@sss.pgh.pa.us> (raw)
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Greg Stark <gsstark@mit.edu> writes:
> On Wed, Apr 20, 2011 at 2:19 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> How would we keep track of the most recent timestamp received from the
>> master without replaying the WAL records?
> Well as we receive them we would have to peek at them to see the time.
> Or we could have the master send its time to the slave as I believe
> Tom has already proposed in the past but I believe didn't choose to
> do?
My idea of how to manage it would be to have walreceiver explicitly
track the clock difference from the master, which it can do since
walsender puts its current time into every message header. You can use
the slave's clock for comparisons so long as you add the appropriate
offset. (The theory here is that the skew won't change very fast ...)
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, gsstark@mit.edu, robertmhaas@gmail.com
Subject: Re: time-delayed standbys
In-Reply-To: <26007.1303309175@sss.pgh.pa.us>
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