| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, MauMau <maumau307(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kevin Grittner <kgrittn(at)ymail(dot)com>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Standalone synchronous master |
| Date: | 2014-01-10 22:47:13 |
| Message-ID: | CAMkU=1xAtZPYRjwr4qtw7bCVDmghXvOhUfgGgKtPrxHBFcVabQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jan 10, 2014 at 2:33 PM, Andres Freund <andres(at)2ndquadrant(dot)com>wrote:
> On 2014-01-10 14:29:58 -0800, Joshua D. Drake wrote:
> > db02 goes down. It doesn't matter why. It is down. db01 continues to
> accept
> > orders, allow people to log into the website and we can still service
> > accounts. The continuity of service continues.
>
> Why is that configuration advantageous over a async configuration is the
> question.
Because it is orders of magnitude less likely to lose transactions that
were reported to have been committed. A permanent failure of the master is
almost guaranteed to lose transactions with async. With auto-degrade, a
permanent failure of the master only loses reported-committed transactions
if it co-occurs with a temporary failure of the replica or the network,
lasting longer than the time out period.
Why, with those requirements, are you using a synchronous
> standby at all?
>
They aren't using synchronous standby, they are using asynchronous standby
because we fail to provide the choice they prefer, which is a compromise
between the two.
Cheers,
Jeff
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