From:
Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To:
Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc:
Simon Riggs <simon(at)2ndQuadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject:
Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled
synchronous replication.
Date:
2011-03-07 14:02:44
Message-ID:
4D74E584.7080409@enterprisedb.com (view raw or flat )
Thread:
2011-03-06 22:51:56 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-06 23:09:53 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-06 23:28:45 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 07:29:48 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 07:48:11 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 07:54:19 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 13:30:34 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 14:02:44 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 14:21:46 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 14:29:04 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-07 15:03:10 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 15:13:46 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-07 15:46:52 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-07 15:51:49 from Andrew Dunstan <andrew(at)dunslane(dot)net>
2011-03-07 16:09:49 from Alvaro Herrera <alvherre(at)commandprompt(dot)com>
2011-03-18 09:27:13 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 13:16:24 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-18 13:30:56 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 13:40:22 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 14:37:26 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 16:03:03 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-18 14:19:18 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 14:52:13 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 15:43:38 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 15:47:46 from Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
2011-03-18 16:19:31 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 16:33:26 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 16:48:57 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 17:35:46 from Greg Stark <gsstark(at)mit(dot)edu>
2011-03-18 19:17:56 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 19:19:06 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 19:29:50 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 19:34:18 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 19:41:00 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 21:08:11 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-18 21:26:00 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-22 20:33:11 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-23 07:27:13 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-23 11:52:22 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-23 12:16:39 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-23 15:24:30 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:18:28 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:24:03 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 21:30:04 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 21:43:32 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 21:48:33 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 22:47:54 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-19 19:27:04 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-25 12:12:05 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 16:27:57 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-18 19:22:20 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 14:19:56 from Markus Wanner <markus(at)bluegap(dot)ch>
2011-03-18 15:52:18 from MARK CALLAGHAN <mdcallag(at)gmail(dot)com>
2011-03-07 15:04:22 from Aidan Van Dyk <aidan(at)highrise(dot)ca>
2011-03-07 14:55:11 from "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
2011-03-06 23:28:13 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2011-03-06 23:36:30 from Jaime Casanova <jaime(at)2ndquadrant(dot)com>
2011-03-06 23:38:30 from Jaime Casanova <jaime(at)2ndquadrant(dot)com>
2011-03-06 23:52:49 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 08:27:16 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 08:44:52 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 09:30:35 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 09:47:20 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-10 21:28:12 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 14:10:03 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-19 01:12:52 from Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
2011-03-23 15:53:30 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-07 09:20:07 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-07 09:28:25 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-07 11:21:39 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-10 20:04:57 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-11 10:46:03 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-17 17:46:37 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-17 17:56:36 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 06:25:06 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 12:25:49 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 14:55:56 from Greg Stark <gsstark(at)mit(dot)edu>
2011-03-18 15:07:23 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 15:40:57 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-25 11:53:15 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-17 17:52:56 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-18 05:45:44 from Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
2011-03-18 07:52:07 from Simon Riggs <simon(at)2ndQuadrant(dot)com>
2011-03-18 12:16:08 from Robert Haas <robertmhaas(at)gmail(dot)com>
2011-03-10 20:44:33 from Robert Haas <robertmhaas(at)gmail(dot)com>
Lists:
pgsql-committers pgsql-hackers
On 07.03.2011 15:30, Andrew Dunstan wrote:
> Previously, Simon said:
>
>> Truly "synchronous" requires two-phase commit, which this never was.
>
> So I too am confused about how it's now become "truly synchronous". Are
> we saying this give the same or better guarantees than a 2PC setup?
The guarantee we have now with synchronous_replication=on is that when
the server acknowledges a commit to the client (ie. when COMMIT command
returns), the transaction is safely flushed to disk on the master and at
least one synchronous standby server.
What you don't get is a guarantee on what happens to transactions that
were not acknowledged to the client. For example, if you pull the power
plug, the transaction that was just being committed might be committed
on the master, but not yet on the standby.
For me, that's enough to call it "synchronous replication". It provides
a useful guarantee to the client. But you could argue for an even
stricter definition, requiring atomicity so that if a transaction is not
successfully replicated for any reason, including crash, it is rolled
back in the master too. That would require 2PC.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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synchronous replication.
