Re: Streaming-only Remastering

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Daniel Farina <daniel(at)heroku(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Streaming-only Remastering
Date: 2012-06-17 20:11:05
Message-ID: 4FDE39D9.5000505@agliodbs.com
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> Instead of using re-synchronization (e.g. repmgr in its relation to
> rsync), I intend to proxy and also inspect the streaming replication
> traffic and then quiesce all standbys and figure out what node is
> farthest ahead. Once I figure out the node that is farthest ahead, if
> it is not a node that is eligible for promotion to the master, I need
> to exchange its changes to nodes that are eligible for promotion[0],
> and then promote one of those, repointing all other standbys to that
> node. This must all take place nominally within a second or thirty.
> Conceptually it is simple, but mechanically it's somewhat intense,
> especially in relation to the inconvenience of doing this incorrectly.

So you're suggesting that it would be great to be able to
double-remaster? i.e. given OM = Original Master, 1S = standby furthest
ahead, NM = desired new master, to do:

1S <--- OM ---> NM

OM dies, then:

1S -----------> NM

until NM is caught up, then

1S <----------- NM

Yes?

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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