From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | MARK CALLAGHAN <mdcallag(at)gmail(dot)com> |
Cc: | Markus Wanner <markus(at)bluegap(dot)ch>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. |
Date: | 2011-03-18 14:19:18 |
Message-ID: | 1300457958.18619.13780.camel@ebony |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-committers pgsql-hackers |
On Fri, 2011-03-18 at 13:16 +0000, MARK CALLAGHAN wrote:
> On Fri, Mar 18, 2011 at 9:27 AM, Markus Wanner <markus(at)bluegap(dot)ch> wrote:
> > Google invented the term "semi-syncronous" for something that's
> > essentially the same that we have, now, I think. However, I full
> > heartedly hate that term (based on the reasoning that there's no
> > semi-pregnant, either).
>
> We didn't invent the term, we just implemented something that Heikki
> Tuuri briefly described, for example:
> http://bugs.mysql.com/bug.php?id=7440
>
> In the Google patch and official MySQL version, the sequence is:
> 1) commit on master
> 2) wait for slave to ack
> 3) return to user
>
> After step 1 another user on the master can observe the commit and the
> following is possible:
> 1) commit on master
> 2) other user observes that commit on master
> 3) master blows up and a user observed a commit that never made it to a slave
>
> I do not think this sequence should be possible in a sync replication
> system. But it is possible in what has been implemented for MySQL.
> Thus it was named semi-sync rather than sync.
Thanks for clearing it up Mark.
We should definitely not be calling what we have "semi-sync". The
semantics are very different.
In PostgreSQL other users cannot observe the commit until an
acknowledgement has been received.
--
Simon Riggs http://www.2ndQuadrant.com/books/
PostgreSQL Development, 24x7 Support, Training and Services
From | Date | Subject | |
---|---|---|---|
Next Message | Markus Wanner | 2011-03-18 14:19:56 | Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. |
Previous Message | Robert Haas | 2011-03-18 14:10:03 | Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. |
From | Date | Subject | |
---|---|---|---|
Next Message | Markus Wanner | 2011-03-18 14:19:56 | Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. |
Previous Message | Jeff Davis | 2011-03-18 14:17:53 | Re: Sync Rep and shutdown Re: Sync Rep v19 |