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Re: Why there are no max_wal_receivers - Mailing list pgsql-general

From 高健
Subject Re: Why there are no max_wal_receivers
Date
Msg-id CAL454F2jwrJ_kZ_msnd-0jXP2H+OdoXpC4_cTr8DOsxQyLWKqA@mail.gmail.com
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In response to Re: Why there are no max_wal_receivers  (Adrian Klaver <adrian.klaver@gmail.com>)
Responses Re: Why there are no max_wal_receivers  (Amit Langote <amitlangote09@gmail.com>)
Re: Why there are no max_wal_receivers  (Adrian Klaver <adrian.klaver@gmail.com>)
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Hello:


 


Thank you all for kindly replying my question.


I read the documentation about pg_basebackup.


The description says:

The server must also be configured with max_wal_senders set high enough to leave at least one session available for the backup.

Dose it mean:

If I am building a one master  -- one slave environment, I need the max_wal_sender to be at least 2.

But I think pg_basebackup just use the one sender process  temporarily, Is that right?


Best Regards



2013/10/7 Adrian Klaver <adrian.klaver@gmail.com>
On 10/06/2013 09:53 PM, Amit Langote wrote:
Hi,

On Mon, Oct 7, 2013 at 12:02 PM, 高健 <luckyjackgao@gmail.com> wrote:
Hello :


I found that for PG9.2.4, there is parameter max_wal_senders,

But there is no parameter of max_wal_receivers.



max_wal_senders is the maximum number of WAL sender processes that a
primary server can create in response to requests from the standby
servers. One WAL sender process is created on the primary server for
each standby which would running the corresponding WAL receiver. So
there is one-to-one mapping between WAL senders and WAL receivers
(standbys).

Just to add, pg_basebackup also counts against the total of receivers:

http://www.postgresql.org/docs/9.3/interactive/app-pgbasebackup.html



--
Amit Langote




--
Adrian Klaver
adrian.klaver@gmail.com

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