Обсуждение: Finding slave WAL application time delay

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Finding slave WAL application time delay

От
Bruce Momjian
Дата:
Someone at OSCON just asked if there is a way to find the _time_ delay
between received and applied WAL.  Right now
pg_last_xlog_replay_location() only reports the information in WAL
scale.  It would be nice to report that in time, e.g. milliseconds.

Because an idle master will not generate WAL, I don't think there is a
way to report the time delay in receiving WAL.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + None of us is going to be here forever. +


Re: Finding slave WAL application time delay

От
Robert Haas
Дата:
On Tue, Jul 20, 2010 at 3:13 PM, Bruce Momjian <bruce@momjian.us> wrote:
> Someone at OSCON just asked if there is a way to find the _time_ delay
> between received and applied WAL.  Right now
> pg_last_xlog_replay_location() only reports the information in WAL
> scale.  It would be nice to report that in time, e.g. milliseconds.

There's probably more than one way you can define this.  See, for
example, previous discussions of max_standby_delay.

> Because an idle master will not generate WAL, I don't think there is a
> way to report the time delay in receiving WAL.

You could certainly come up with a sensible definition for this,
though there are also nonsensical ones.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company