[pgpool-general: 3072] Re: Failover - new primary selection process?

[John Scalia]

Sorry for the delay in getting this to you, Ishii-san. All of my VM's were powered down after the chassis received a weekend upgrade.

The log message I was referring to is (from a failover test performed last week):

2014-07-23 24:54:56 LOG: pid 70166: pgpool_down: I'm *oldest* so standing for master

This is written almost immediately before ifconfig brings up the IP alias address and before the failover_command is executed. That's what led me to my comments, although as I 
admitted, I had not read the code in this area. If selection is just by sequential node ID, that's a little misleading.

On 7/28/2014 7:05 AM, Tatsuo Ishii wrote:
> What are you referring to error message? I do not see anything like
> "I'm the oldest, so assuming the master role." message in pgpool-II
> code anywhere.
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
>> Then, I hate to say it, Ishii-san, but your log message is a bit misleading. For instance, I always see a message during a failover where the standby claims, "I'm the oldest, so assuming the master role." So, maybe it should just "I have the lowest remaining node number, so I'm assuming the master role."  That wouldn't imply logic based on time, only sequences.
>>
>> Sent from my iPad
>>
>>> On Jul 28, 2014, at 3:20 AM, Tatsuo Ishii <ishii at postgresql.org> wrote:
>>>
>>> No. Pgpool-II has no idea which server has been running longer.
>>>
>>> Pgpool-II has no built-in logic to choose next
>>> to-be-primary-candidate. Which slave node will be promoted next time
>>> is completely depending on your failover script. In general most
>>> people specifies the candidate slave as the master node, which has the
>>> yonguest node number among live slave nodes (%m in failover script).
>>> Example: you have node 0 primary, node 1&2 standby.
>>>
>>> 1) node 0 is down.
>>>
>>> 2) node 1 is chosen as the next primary because it's the youngest live
>>> node (master).
>>>
>>> 3) node 1 is down.
>>>
>>> 4) node 2 is chosen as the next primary because it's the youngest live
>>> node (master).
>>>
>>> Best regards,
>>> --
>>> Tatsuo Ishii
>>> SRA OSS, Inc. Japan
>>> English: http://www.sraoss.co.jp/index_en.php
>>> Japanese:http://www.sraoss.co.jp
>>>
>>>> Hey jay, thank you for the replay.
>>>> Is this is a formal conclusion? Maybe the oldest is the one with the
>>>> smaller ID ?
>>>>
>>>>
>>>>
>>>>> On Sun, Jul 27, 2014 at 2:50 PM, <jayknowsunix at gmail.com> wrote:
>>>>>
>>>>> Guy,
>>>>>
>>>>> I run a master with 2 slaves. During a failover, I always see the oldest
>>>>> slave promoted to master. So, the selection is based on the server which
>>>>> has been running longer.
>>>>>
>>>>> --
>>>>> Jay
>>>>>
>>>>> Sent from my iPad
>>>>>
>>>>>> On Jul 27, 2014, at 3:48 AM, Guy Meler <melguy at gmail.com> wrote:
>>>>>>
>>>>>> Hey :)
>>>>>> In master/slave mode, what is the algorithm for choosing the next
>>>>> available primary backend?
>>>>>> I want to make sure that if primary in site A goes down, than the next
>>>>> available primary is in the same site.
>>>>>> Thank you
>>>>>>
>>>>>> _______________________________________________
>>>>>> pgpool-general mailing list
>>>>>> pgpool-general at pgpool.net
>>>>>> http://www.pgpool.net/mailman/listinfo/pgpool-general

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