pg_rewind

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pg_rewind

soumik.bhattacharjee

Hi Experts,

 

Initial setup was done using streaming replication and then promoted the STANDBY to MASTER.

 

I am trying to make my previous Master as Master by roll backing the changes happen into Standby

 

 

In Original MASTER I am running below –

 

/usr/lib/postgresql/12/bin$ ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432' -P

pg_rewind: fatal: could not connect to server: fe_sendauth: no password supplied

 

I'm not sure why this keeps happening.

 

 

Thanks..

 

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Re: pg_rewind

Laurenz Albe
On Thu, 2020-01-23 at 15:39 +0000, [hidden email] wrote:
> I am trying to make my previous Master as Master by roll backing the changes happen into Standby
>
> In Original MASTER I am running below –
>
> /usr/lib/postgresql/12/bin$ ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432' -P
> pg_rewind: fatal: could not connect to server: fe_sendauth: no password supplied
>
> I'm not sure why this keeps happening.

Because you used the wrong user or didn't specify a password?

Try

   --source-server='host=<IP Address> port=5432 user=... password=...'

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com



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RE: pg_rewind

soumik.bhattacharjee
Thanks for your suggestion, I need now to make "wal_log_hints = on"

-----Original Message-----
From: Laurenz Albe <[hidden email]>
Sent: donderdag 23 januari 2020 16:56
To: Bhattacharjee, Soumik <[hidden email]>; [hidden email]; [hidden email]
Subject: Re: pg_rewind

On Thu, 2020-01-23 at 15:39 +0000, [hidden email] wrote:
> I am trying to make my previous Master as Master by roll backing the changes happen into Standby
>
> In Original MASTER I am running below –
>
> /usr/lib/postgresql/12/bin$ ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432' -P
> pg_rewind: fatal: could not connect to server: fe_sendauth: no password supplied
>
> I'm not sure why this keeps happening.

Because you used the wrong user or didn't specify a password?

Try

   --source-server='host=<IP Address> port=5432 user=... password=...'



Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

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RE: pg_rewind

soumik.bhattacharjee
In reply to this post by Laurenz Albe


-----Original Message-----
From: Laurenz Albe <[hidden email]>
Sent: donderdag 23 januari 2020 16:56
To: Bhattacharjee, Soumik <[hidden email]>; [hidden email]; [hidden email]
Subject: Re: pg_rewind


>
> In Original MASTER I am running below –
>
> /usr/lib/postgresql/12/bin$ ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432' -P
> pg_rewind: fatal: could not connect to server: fe_sendauth: no password supplied
>
> I'm not sure why this keeps happening.

Because you used the wrong user or didn't specify a password?

Try

   --source-server='host=<IP Address> port=5432 user=... password=...'


--
Thanks for your suggestion, I made the "wal_log_hints = on".

I set the "wal_log_hints = on" , but enabling this parameter "on" in new MASTER(old SLAVE) needs a restart-- which I cannot do as all application transactions are going on there now.

Also I used pg_rewind in old MASTER(which now I want to make as new SLAVE) and it was successful, but this also needs restart of new MASTER(old SLAVE) which is again an issue.

Command used: ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432 user=postgres password=xxxx

Could you please suggest how to get this to work to keep the MASTER(old SLAVE) up & running and make the old MASTER(new SLAVE)


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Re: pg_rewind

Laurenz Albe
On Mon, 2020-01-27 at 16:01 +0000, [hidden email] wrote:
> I set the "wal_log_hints = on" , but enabling this parameter "on" in new MASTER(old SLAVE) needs a restart--
> which I cannot do as all application transactions are going on there now.
>
> Also I used pg_rewind in old MASTER(which now I want to make as new SLAVE) and it was successful,
> but this also needs restart of new MASTER(old SLAVE) which is again an issue.
>
> Command used: ./pg_rewind -D $PGDATA --source-server='host=<IP Address> port=5432 user=postgres password=xxxx
>
> Could you please suggest how to get this to work to keep the MASTER(old SLAVE) up & running and make the old MASTER(new SLAVE)

If you want to use "pg_rewind", you have to plan for that ahead of time
by either using data page checksums or enabling "wal_log_hints".

The first requires longer don time, the second a restart.
There is no way to do that retroactively.

Just use "pg_basebackup" to create a new standby, and enable
"wal_log_hints" next time you get a chance to restart.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com