Subject: Re: Replication
To: Masahiko Sawada <sawada.mshk@gmail.com>
References: 
 <CAN1xZseiqNRh1ZE0seVk7UuHeWvFBEWG+FcW7Xfm_Nv=d+fPGw@mail.gmail.com>
 <5752DE6A.7010706@2ndquadrant.fr>
 <CAD21AoCdugbzq8Hc37f58T-8D8JCLYq=EBCxYYoYT+b61PZY0w@mail.gmail.com>
Cc: Bertrand Paquet <bertrand.paquet@doctolib.fr>,
 pgsql-general@postgresql.org
From: Vik Fearing <vik@2ndquadrant.fr>
Message-ID: <575532DA.2010801@2ndquadrant.fr>
Date: Mon, 6 Jun 2016 10:22:50 +0200
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On 06/06/16 09:54, Masahiko Sawada wrote:
> On Sat, Jun 4, 2016 at 10:58 PM, Vik Fearing <vik@2ndquadrant.fr> wrote:
>> On 02/06/16 15:32, Bertrand Paquet wrote:
>>> Hi,
>>>
>>> On an hot standby streaming server, is there any way to know, in SQL, to
>>> know the ip of current master ?
>>
>> No.
>>
>>> The solution I have is to read the recovery.conf file to find
>>> primary_conninfo,
>>
>> That is currently the only solution.  There are plans to allow SQL
>> access to the parameters in recovery.conf (or to merge them into
>> postgresql.conf) but that's not currently possible.
> 
> It might not be a right way but how about using pg_read_file()?
> postgres(1)=# select regexp_replace(pg_read_file('recovery.conf'),
> '.*primary_conninfo = (.*)', '\1');
>                   regexp_replace
> ---------------------------------------------------
>  'host=localhost port=5550 application_name=node1'+
> 
> (1 row)
> 
> You can get the master server information via SQL from standby server.

This is a good idea, but suffers the same problem that Bertrand has with
looking at the file a different way: if the file was changed but the
standby server has not been restarted, it's (potentially) not going to
be the correct information.
-- 
Vik Fearing                                          +33 6 46 75 15 36
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support


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