Re: [PATCH] votequorum: enhance auto_tie_breaker

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On 02/06/2014 05:13 PM, Christine Caulfield wrote:
> On 05/02/14 16:02, Jan Friesse wrote:
>> Chrissie,
>> patch looks good but what will happen in following scenario:
>>

Unless I made coding errors (entirely possible) in ATB pre-this-patch:

>> - 4 nodes (A B C D) and atb list is (A B C D).
>> - A B and C D will split. So A B will get quorum

right

>> - C will split from D

both are unquorate at this stage.

>> - C will join D. So "previous" partition is C (for D node) and D (for C)

C and D are both unquorate. even if they rejoin they will still remain
unquorate.

ATB should only work:
- previous partition was quorate
- there is a 50/50 split
- partition that has "preferred node" will win.


>> node, and as you can see, no A or B. So according to comment, it will
>> vote?
>>
> 
> Hmm good point. Maybe I need to make the algorithm dependant on the
> previous membership list being more (maybe even twice as much) as the
> current one. I'll have a think.

Unless you changed behaviour in your patch, I am not sure I see the
point Jan is trying to make here.

Fabio

> 
> Thanks
> Chrissie
> 
> 
>> Honza
>>
>> Christine Caulfield napsal(a):
>>> This patch adds more flexibility to the auto_tie_breaker feature of
>>> votequorum. With this, not only can the lowest nodeid be used as
>>> a tie breaker, but also the highest, or a node from a nominated list.
>>>
>>> If there is a list of nodes, the first node in the list that was not
>>> part of the previous partition is used. This allows the user to
>>> specify a preferred set of nodes but prevents a split-brain if the
>>> cluster divides evenly with a node in each half.
>>>
>>> Signed-Off-By: Christine Caulfield <ccaulfie@xxxxxxxxxx>
>>>
>>>
>>>
>>> _______________________________________________
>>> discuss mailing list
>>> discuss@xxxxxxxxxxxx
>>> http://lists.corosync.org/mailman/listinfo/discuss
>>>
>>
> 
> _______________________________________________
> discuss mailing list
> discuss@xxxxxxxxxxxx
> http://lists.corosync.org/mailman/listinfo/discuss

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