From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | Aidan Van Dyk <aidan(at)highrise(dot)ca>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Sync Rep for 2011CF1 |
Date: | 2011-01-30 16:44:24 |
Message-ID: | AANLkTimcwkbmL9qxiWRsCRA0CoFt5_ePE97CapF7xiw7@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Sat, Jan 22, 2011 at 8:31 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Fri, 2011-01-21 at 13:32 -0500, Robert Haas wrote:
>
>> One idea might be to wait both before and after commit. If
>> allow_standalone_primary is off, and a commit is attempted, we check
>> whether there's a slave connected, and if not, wait for one to
>> connect. Then, we write and sync the commit WAL record. Next, we
>> wait for the WAL to be ack'd. Of course, the standby might disappear
>> between the first check and the second, but it would greatly reduce
>> the possibility of the master being ahead of the standby after a
>> crash, which might be useful for some people.
>
> I like this idea.
>
> I think it would be too invasive to make a check before we insert each
> WAL record, as Aidan suggests. Even if we did that, you aren't protected
> when a standby goes down because you'll still have written half a
> transaction and still be waiting.
>
> So I propose that
>
> if (!allow_standalone_primary)
> ConfirmSyncRepAvailable();
>
> before PreCommit_Notify(). That puts transaction into a wait state that
> lasts until a sync rep standby is available. Note that it is before the
> actual commit, so if we decide we need to we can cancel those
> transactions and have them properly abort.
>
> I won't add that code yet, in case better ideas emerge.
>
> There is no support for preventing connections at startup, so I will
> remove that completely, now.
Time's running short - do you have an updated patch?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
From | Date | Subject | |
---|---|---|---|
Next Message | Magnus Hagander | 2011-01-30 16:52:00 | Re: mingw 64 build |
Previous Message | Andrew Dunstan | 2011-01-30 15:47:53 | mingw 64 build |