On 06/25/2012 01:17 PM, David Kerr wrote:
Howdy,
When calculating Replication lag, I know that we have to compare the
pg_current_xlog_location
to pg_last_xlog_receive_location, etc. but what I'm trying to figure out is
what are
the units that I'm left with after the calculation.
(i.e., does the xlog_location imply some time value?)
Here's the output of the (slightly modified script)
Master: 5003964876715
Receive: 5003964876715
Replay: 5003964765203
receive.value 0
apply.value 111512
111512 isn't inherently useful to me on its own.
Any tips?
How about now()-pg_last_xact_replay_timestamp() (however this can be a
large number if there have not been any recent transactions on the
master). I suppose you could do something like:
case when pg_last_xlog_receive_location() =
pg_last_xlog_replay_location() then '0 seconds'::interval
else now()-pg_last_xact_replay_timestamp() end as log_delay;
But I'm wrapping my head around some replication issues myself so others
may have better ideas or corrections.
Cheers,
Steve
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