| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Jim Nasby <jim(at)nasby(dot)net> |
| Cc: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Hannu Krosing <hannu(at)2ndQuadrant(dot)com>, Florian Pflug <fgp(at)phlo(dot)org>, Josh Berkus <josh(at)agliodbs(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Amit Kapila <amit(dot)kapila16(at)gmail(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: | 2014-01-13 21:18:21 |
| Message-ID: | 20140113211821.GB5838@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-01-13 15:14:21 -0600, Jim Nasby wrote:
> On 1/13/14, 12:21 PM, Joshua D. Drake wrote:
> >
> >On 01/13/2014 10:12 AM, Hannu Krosing wrote:
> >>>>In other words, if we're going to have auto-degrade, the most
> >>>>intelligent place for it is in
> >>>>RepMgr/HandyRep/OmniPITR/pgPoolII/whatever. It's also the *easiest*
> >>>>place. Anything we do *inside* Postgres is going to have a really,
> >>>>really hard time determining when to degrade.
> >>>+1
> >>>
> >>>This is also how 2PC works, btw - the database provides the building
> >>>blocks, i.e. PREPARE and COMMIT, and leaves it to a transaction manager
> >>>to deal with issues that require a whole-cluster perspective.
> >>>
> >>
> >>++1
> >
> >+1
>
> Josh, what do you think of the upthread idea of being able to recover in-progress transactions that are waiting when we turn off sync rep? I'm thinking that would be a very good feature to have... and it's not something you can easily do externally.
I think it'd be a fairly simple patch to re-check the state of syncrep
config in SyncRepWaitForLsn(). Alternatively you can just write code to
iterate over the procarray and sets Proc->syncRepState to
SYNC_REP_WAIT_CANCELLED or such.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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