From: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: amul sul <sulamul@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [Patch] ALTER SYSTEM READ ONLY
Date: Thu, 18 Jun 2020 12:35:03 +0200
Message-ID: <20200618123503.4d2c5ae5@firost> (raw)
In-Reply-To: <CA+TgmobHeJ0Bg0QmgTtpO2AvmJOQOgafHf__UNcCQKA2ybyYQw@mail.gmail.com>
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<CAA4eK1+5BDNS08XKXR7UPkq4tDaV66wyZia4kDMvRUm=a_A=Gg@mail.gmail.com>
<1445158.1592405895@sss.pgh.pa.us>
<CA+TgmobHeJ0Bg0QmgTtpO2AvmJOQOgafHf__UNcCQKA2ybyYQw@mail.gmail.com>
On Wed, 17 Jun 2020 12:07:22 -0400
Robert Haas <robertmhaas@gmail.com> wrote:
[...]
> > Commands that involve a whole
> > bunch of subtle interlocking --- and, therefore, aren't going to work if
> > anything has gone wrong already anywhere in the server --- seem like a
> > particularly poor thing to be hanging your HA strategy on.
>
> It's important not to conflate controlled switchover with failover.
> When there's a failover, you have to accept some risk of data loss or
> service interruption; but a controlled switchover does not need to
> carry the same risks and there are plenty of systems out there where
> it doesn't.
Yes. Maybe we should make sure the wording we are using is the same for
everyone. I already hear/read "failover", "controlled failover", "switchover" or
"controlled switchover", this is confusing. My definition of switchover is:
swapping primary and secondary status between two replicating instances. With
no data loss. This is a controlled procedure where all steps must succeed to
complete.
If a step fails, the procedure fail back to the original primary with no data
loss.
However, Wikipedia has a broader definition, including situations where the
switchover is executed upon a failure: https://en.wikipedia.org/wiki/Switchover
Regards,
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To: pgsql-hackers@postgresql.org
Cc: jgdr@dalibo.com, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, amit.kapila16@gmail.com, sulamul@gmail.com
Subject: Re: [Patch] ALTER SYSTEM READ ONLY
In-Reply-To: <20200618123503.4d2c5ae5@firost>
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