Re: Streaming replication, retrying from archive

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Streaming replication, retrying from archive
Date: 2010-01-14 14:39:59
Message-ID: 9837222c1001140639q365ca452p8daf7301133d5317@mail.gmail.com
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On Thu, Jan 14, 2010 at 15:36, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Thu, Jan 14, 2010 at 9:15 AM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
>> Imagine this scenario:
>>
>> 1. Master is up and running, standby is connected and streaming happily
>> 2. Network goes down, connection is broken.
>> 3. Standby falls behind a lot. Old WAL files that the standby needs are
>> archived, and deleted from master.
>> 4. Network is restored. Standby reconnects
>> 5. Standby will get an error because the WAL file it needs is not in the
>> master anymore.
>>
>> What will currently happen is:
>>
>> 6, Standby retries connecting and failing indefinitely, until the admin
>> restarts it.
>>
>> What we would *like* to happen is:
>>
>> 6. Standby fetches the missing WAL files from archive, then reconnects
>> and continues streaming.
>>
>> Can we fix that?
>
> Just MHO here, but this seems like a bigger project than we should be
> starting at this stage of the game.

+1.

We want this eventually (heck, it'd be awesome!), but let's get what
we have now stable first.

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/

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