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Re: synchronous_commit and remote_write

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: synchronous_commit and remote_write
Date: 2012-05-09 12:48:55
Message-ID: CA+TgmoaR4bwNu=y6U+WwtvcLxwsQjTcBfBs09ysOxfusE=m=-A@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, May 9, 2012 at 7:29 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> Let me point out that our documentation says nothing about it being
> written to the kernel --- it just says "has received the commit record
> of the transaction to memory."

Maybe remote_receive would be better.  If we're actually writing it
back to the kernel before acknowledging the commit, that seems like an
implementation defect more than anything else, since it does not -
AFAICS - provide any additional, useful guarantee.

Another thing I've been wondering is whether, perhaps, we ought to
keep synchronous_commit tri-valued: on/local/off, and have a separate
GUC for synchronous_replication_mode.  It's a bit arbitrary that "on"
happens to mean remote fsync rather than remote write/receive.

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

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