From: Hannu Krosing <hannu@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Simon Riggs <simon@2ndquadrant.com>
Cc: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Sync Rep Design
Date: Fri, 31 Dec 2010 08:50:07 +0100
Message-ID: <4D1D8B2F.5070001@2ndquadrant.com> (raw)
In-Reply-To: <AANLkTi=SvN2KQ1Tzh-tRKcXD0i2FyWFBbbR=kXXdepqN@mail.gmail.com>
References: <1293729972.1892.23804.camel@ebony>
<4D1CC47E.7050207@kaltenbrunner.cc>
<1293735853.1892.24886.camel@ebony>
<AANLkTi=SvN2KQ1Tzh-tRKcXD0i2FyWFBbbR=kXXdepqN@mail.gmail.com>
On 30.12.2010 22:27, Robert Haas wrote:
> On Thu, Dec 30, 2010 at 2:04 PM, Simon Riggs<simon@2ndquadrant.com> wrote:
>> synchronous_replication (boolean)
>> Specifies whether transaction commit will wait for WAL records
>> to be replicated before the command returns a "success"
>> indication to the client.
> The word "replicated" here could be taken to mean different things,
> most obviously:
>
> - slave has received the WAL
> - slave has fsync'd the WAL
> - slave has applied the WAL
Perhaps the level of "replication guarantee" should be decided on the
slave side, by
having a configuration parameter there
report_as_replicated = received|written_to_disk|fsynced|applied
for different types of hosts may have wildly different guarantees and
performance
parameters for these. One could envision a WAL-archive type "standby"
which is
there for data persistence only will and never "apply" WAL.
of couse we could put a bitmap in the status update messages from slave
and have
some quorum on options on master for when the data is "in sync", say
"need 5 received
or (1 applied and 1 fsynced)", but I am pretty sure that trying to get
anywhere with this
before applying the basic sync rep patch would push back sync rep to at
least 9.2 if not 9.5
---------------------
Hannu Krosing
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To: pgsql-hackers@postgresql.org
Cc: hannu@2ndquadrant.com, robertmhaas@gmail.com, simon@2ndquadrant.com, stefan@kaltenbrunner.cc
Subject: Re: Sync Rep Design
In-Reply-To: <4D1D8B2F.5070001@2ndquadrant.com>
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