[pgpool-general: 5317] Re: About failover execution and master node detection
Lazaro Garcia
lazaro3487 at gmail.com
Thu Feb 9 18:57:21 JST 2017
Thanks very much for the help.
-----Mensaje original-----
De: Tatsuo Ishii [mailto:ishii at sraoss.co.jp]
Enviado el: jueves, 9 de febrero de 2017 01:19 a. m.
Para: lazaro3487 at gmail.com
CC: pgpool-general at pgpool.net
Asunto: Re: [pgpool-general: 5302] About failover execution and master node
detection
> Thank you very much for the explanation, I think this question could
> be added in the FAQs.
>
> Is there any plan to implement some functionality for selecting the
> standby with less delay in the replica?
You can do it today within your fail over script by using
pg_last_xlog_receive_location() or some such.
Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp
> -----Mensaje original-----
> De: Tatsuo Ishii [mailto:ishii at sraoss.co.jp] Enviado el: miércoles, 8
> de febrero de 2017 12:10 a. m.
> Para: lazaro3487 at gmail.com
> CC: pgpool-general at pgpool.net
> Asunto: Re: [pgpool-general: 5302] About failover execution and master
> node detection
>
> %m is the new master node chosen by Pgpool-II. It is the node being
> assigned the youngest (smallest) node id which is alive.
>
> For example if you have 3 nodes, namely node 0, 1, 2. Suppose node 1
> the primary and all of them are healthy (no down node). If node 1
> fails, failover_command is called with %m = 0.
>
> If node 0 is down, %m would be 2.
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
>> Thanks for your answer.
>>
>> In the failover_command configuration parameter, %m is the new master
>> selected by pgpool. With 2 standby servers, what node is selected as
> master?
>>
>> failover_command = ''
>> # Executes this command at failover
>> # Special values:
>> # %d = node id
>> # %h = host name
>> # %p = port number
>> # %D = database cluster path
>> # %m = new master node id
>> # %H = hostname of the new master
> node
>> # %M = old master node id
>> # %P = old primary node id
>> # %r =
>> new master port number
>> # %R =
>> new master database cluster path
>> # %% = '%' carácter
>>
>> Regards.
>>
>> -----Mensaje original-----
>> De: Tatsuo Ishii [mailto:ishii at sraoss.co.jp] Enviado el: martes, 7 de
>> febrero de 2017 04:51 a. m.
>> Para: lazaro3487 at gmail.com
>> CC: pgpool-general at pgpool.net
>> Asunto: Re: [pgpool-general: 5302] About failover execution and
>> master node detection
>>
>>> I am Reading the pgpool documentation and i have a doubt related to
>>> failover and selecting a new master node.
>>>
>>>
>>>
>>> I want to create a cluster with more than 2 nodes for instance 3
>>> nodes. The question is when the backend shuts down, the new primary
>>> selected by pgpool and sended to the failover command is the closest
>>> node to previous master, in terms of replication delay?
>>
>> Probably you are misunderstanding. Pgpool-II does *not* automatically
>> choose new primary. It's totally up to you how to select the new
>> primary node in the failover command script. In other word, the logic
>> to choose the new primary node should be explicitly coded in the
>> failover
> command script.
>>
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
>>
>
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