Re: Streaming Replication Without Downtime

[Achilleas Mantzios <achill@xxxxxxxxxxxxxxxxxxxxx>]

On 21/02/2017 01:49, Venkata B Nagothi wrote:

On Tue, Feb 21, 2017 at 6:53 AM, Gabriel Ortiz Lour <ortiz.admin@xxxxxxxxx> wrote:

Hi!

  Thanks for pointing out pg_basebackup

  The issue I'm facing now is about missing WAL files.

  What i'm doing:

# su postgres -c 'pg_basebackup -D /var/lib/postgresql/9.1/main/ -x -h master -U sa_rep' ; service postgresql start

Ok but between pg_basebackup and service postgresql start you must configure the db as a stand by. You need to copy a pre-configured recovery file into the data dir (or whatever debian demands) and then start. In 9.3 there is --write-recovery-conf which does this for you.

  The idea is to call "postgresql start" as soon as pg_basebackup ends.

  But I'm getting the following error:

  FATAL: could not receive data from WAL stream: FATAL: requested WAL segment XXXXXXX has already been removed

  Shoud I just increase 'wal_keep_segments' ?

Yes, that is the way to go. But, you need to know what number you need to increase the wal_keep_segments to ?

Which purely depends on the number of WALs being generated. Which version of PostgreSQL are you using by the way ?

Apparently 9.1. In 9.2 you can always use -X stream , thus making increasing of the wal_keep_segments redundant.

 

  If I do so, do I need do restart the master or just a reload will do it?

No need to restart, "reload" will do.

Venkata B N

Database consultant

 

---------- Forwarded message ----------
From: Achilleas Mantzios <achill@xxxxxxxxxxxxxxxxxxxxx>
Date: 2017-02-17 11:20 GMT-02:00
Subject: Re: Streaming Replication Without Downtime
To: pgsql-general@xxxxxxxxxxxxxx

Gabriel you are thinking this in the correct way, but its really :

pg_basebackup -D <your data dir> --write-recovery-conf --progress --xlog-method=stream -h <your primary db server>
then you just edit recovery.conf (if needed), tweak postgersql.conf (if needed) and start the standby .

On 17/02/2017 15:09, Gunnar "Nick" Bluth wrote:

(sorry for the toppost, mobile device)
What you're looking for is pg_basebackup with - - xlog=stream, I guess.

Regards,

Nick

Am 17. Februar 2017 14:06:36 MEZ schrieb Gabriel Ortiz Lour <ortiz.admin@xxxxxxxxx>:

Hi all,

  I've been searching for a way to initialize a new Hot Standby node with Streaming Replication withou the need for stop or even restarting the master.

  Of course the master is already with the needed SR configs.

  I know I have to use pg_start_backup/pg_stop_backup, but i'd like some tips, or a link to some tutorial, with the order of the steps.

  I assume will be something like:

-  configure Slave for SR

-  pg_start_backup()

-  rsync PGDATA to slave

-  start PG on the slave

-  pg_stop_backup()

  Anything i'm thinking wrong?

Thanks in advance,

Gabriel

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-- 
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt

-- 
Achilleas Mantzios
IT DEV Lead
IT DEPT
Dynacom Tankers Mgmt