| From: | Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Andres Freund <andres(at)2ndquadrant(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(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: | 2014-01-13 13:12:43 |
| Message-ID: | BF2827DCCE55594C8D7A8F7FFD3AB7713DDB908E@SZXEML508-MBX.china.huawei.com |
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| Lists: | pgsql-hackers |
> On Sun, Jan 12, Amit Kapila wrote:
> >> How would that work? Would it be a tool in contrib? There already
> >> is a timeout, so if a tool checked more frequently than the timeout,
> >> it should work. The durable notification of the admin would happen
> >> in the tool, right?
> >
> > Well, you know what tool *I'm* planning to use.
> >
> > Thing is, when we talk about auto-degrade, we need to determine
> things
> > like "Is the replica down or is this just a network blip"? and take
> > action according to the user's desired configuration. This is not
> > something, realistically, that we can do on a single request.
> Whereas
> > it would be fairly simple for an external monitoring utility to do:
> >
> > 1. decide replica is offline for the duration (several poll attempts
> > have failed)
> >
> > 2. Send ALTER SYSTEM SET to the master and change/disable the
> > synch_replicas.
>
> Will it possible in current mechanism, because presently master will
> not accept any new command when the sync replica is not available?
> Or is there something else also which needs to be done along with
> above 2 points to make it possible.
Since there is not WAL written for ALTER SYSTEM SET command, then
it should be able to handle this command even though sync replica is
not available.
Thanks and Regards,
Kumar Rajeev Rastogi
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