Re: Dividing progress/debug information in pg_standby, and stat before copy

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Magnus Hagander <magnus(at)hagander(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Smith <greg(at)2ndquadrant(dot)com>, Selena Deckelmann <selenamarie(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: Dividing progress/debug information in pg_standby, and stat before copy
Date: 2010-01-26 10:12:25
Message-ID: 4B5EC009.4070709@enterprisedb.com
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Magnus Hagander wrote:
> I think there are definite use-cases for pg_standby as well, even when
> we have SR. SR requires you to have a reasonably reliable network
> connection that lets you do an arbitrary TCP connection. There are a
> lot of scenarios that could still use the
> "here's-a-file-you-choose-how-to-get-it-over-to-the-other-end" style
> transfer, and that don't necessarily care that there is a longer
> delay.

With the changes to the retry-logic that were discussed (see
http://archives.postgresql.org/message-id/4B5758ED.1060703@enterprisedb.com,
I intend to commit that tomorrow), if standby_mode=on, the server will
keep retrying to restore the next segment using restore_command until
it's found, or the trigger file is found.

*That* makes pg_standby obsolete, not streaming replication per se.
Setting standby_mode=on, with a valid restore_command using e.g 'cp' and
no connection info for walreceiver is more or less the same as using
pg_standby.

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

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