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Subject: Re: PostgreSQL replication failover
From: John Wiencek <jwiencek3@comcast.net>
In-Reply-To: 
 <trinity-4813039b-0953-4d98-a901-cc0a6807c285-1610612162770@3c-app-gmx-bap12>
Date: Thu, 14 Jan 2021 09:03:38 -0600
Cc: Ganesh Korde <ganeshakorde@gmail.com>,
 Pepe TD Vo <pepevo@yahoo.com>,
 Pgsql-admin <pgsql-admin@lists.postgresql.org>,
 Laurenz Albe <laurenz.albe@cybertec.at>
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References: 
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 <976875a5adf1c1cda0d55e6da0313f30dc8059f6.camel@cybertec.at>
 <526397214.877472.1610544243527@mail.yahoo.com>
 <CAPNyb0UMysUm2KzYoy==HtNXbq2LjJanxTzxBRJjdPXt4W418A@mail.gmail.com>
 <trinity-4813039b-0953-4d98-a901-cc0a6807c285-1610612162770@3c-app-gmx-bap12>
To: Jan Peters <haseningo@gmx.de>
Precedence: bulk

Hi

You can use repmgr, which is free,  or EFM which requires a =
subscription.

John=20

> On Jan 14, 2021, at 2:16 AM, Jan Peters <haseningo@gmx.de> wrote:
>=20
> Hello,
>=20
> thank you very much for the answers.=20
> Can you tell me some tools, but they must be available for s390 =
ZLinux.
> For our purposes in redhat linux=20
>=20
>=20
> Gesendet: Mittwoch, 13. Januar 2021 um 19:46 Uhr
> Von: "Ganesh Korde" <ganeshakorde@gmail.com>
> An: "Pepe TD Vo" <pepevo@yahoo.com>
> Cc: "Jan Peters" <haseningo@gmx.de>, pgsql-admin@lists.postgresql.org, =
"Laurenz Albe" <laurenz.albe@cybertec.at>
> Betreff: Re: PostgreSQL replication failover
>=20
> You can use different tools which detects if primary fails and =
automatically promotes standby.=20
> =20
> To assure all data on standby you should use synchronous replication.=20=

>=20
> On Wed, 13 Jan 2021, 6:54 pm Pepe TD Vo, =
<pepevo@yahoo.com[mailto:pepevo@yahoo.com]> wrote:
>=20
>>> If you shut down the primary server cleanly, all changes will be =
replicated,so you should be good.
>=20
>>> During a failover, that is, if the primary suddenly fails, there is =
always
> the possibility that you lose some transactions, unless you use =
synchronous
> you said above which I don't need to run promote to make it failover =
as long as I set synchronous on?   The last couple of weeks I have a =
failure on the primary server and can't run on a slave. It picks up as =
reading mode only.
> =20
>=20
> Bach-Nga
>=20
> No one in this world is pure and perfect.  If you avoid people for =
their mistakes you will be alone. So judge less, love, and forgive more.
> To call him a dog hardly seems to do him justice though in as much as =
he had four legs, a tail, and barked, I admit he was, to all outward =
appearances. But to those who knew him well, he was a perfect gentleman =
(Hermione Gingold)
> **Live simply **Love generously **Care deeply **Speak kindly.
> *** Genuinely rich *** Faithful talent *** Sharing success
> =20
> =20
> =20
> =20
>=20
> On Wednesday, January 13, 2021, 06:25:53 AM EST, Laurenz Albe =
<laurenz.albe@cybertec.at[mailto:laurenz.albe@cybertec.at]> wrote:
> =20
> =20
>=20
> On Wed, 2021-01-13 at 09:27 +0100, Jan Peters wrote:
>> we are running postgresqlserver on s390 zLinux machines. The =
distribution
>>   is RedHat 7 and RedHat 8, so we do not have the many x86 tools =
available.
>>=20
>> We always run 2 instances with a replication (streaming) async mode, =
the replica
>>   is in hot_standby and we use it for read-only accesses. About the =
setup we have the following question:
>>=20
>> How is an orderly failover accomplished? Our current procedure is.
>>=20
>> 1. primary stop
>> 2. promote replica to primary
>> 3. create standby.signal on old primary
>> 4. change primary_conninfo on old primary
>> 5. start old primary as new replica
>>=20
>> Is this processing correct? Are there any other steps that simplify a =
failover?
>>   How can we be sure that all changes have been transferred from the =
old master to the replica?
>=20
> What you describe is not a failover, but a switchover.
>=20
> If you shut down the primary server cleanly, all changes will be =
replicated,
> so you should be good.
>=20
> During a failover, that is, if the primary suddenly fails, there is =
always
> the possibility that you lose some transactions, unless you use =
synchronous
> replication.
>=20
> Yours,
> Laurenz Albe
> --
> Cybertec | =
https://www.cybertec-postgresql.com[https://www.cybertec-postgresql.com]
>=20
>=20
> =20
>=20
>=20