Re: Synchronous Log Shipping Replication

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndQuadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Markus Wanner <markus(at)bluegap(dot)ch>, ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Synchronous Log Shipping Replication
Date: 2008-09-09 14:17:34
Message-ID: 48C6857E.4000402@enterprisedb.com
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Tom Lane wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
>> On Tue, 2008-09-09 at 08:24 -0400, Tom Lane wrote:
>>> "Agreed"? That last restriction is a deal-breaker.
>
>> OK, I should have said *if wal_buffers are full* XLogInsert() cannot
>> advance to a new page while we are waiting to send or write. So I don't
>> think its a deal breaker.
>
> Oh, OK, that's obvious --- there's no place to put more data.

Each WAL sender can keep at most one page locked at a time, right? So,
that should never happen if wal_buffers > 1 + n_wal_senders.

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

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