[Pacemaker] pacemaker/dlm problems

[Andrew Beekhof]

On Mon, Oct 3, 2011 at 7:29 PM, Vladislav Bogdanov <bubble at hoster-ok.com> wrote:
> 03.10.2011 10:56, Andrew Beekhof wrote:
>>
>> On Mon, Oct 3, 2011 at 3:34 PM, Vladislav Bogdanov<bubble at hoster-ok.com>
>>  wrote:
>>>
>>> 03.10.2011 04:41, Andrew Beekhof wrote:
>>> [...]
>>>>>>>
>>>>>>> If pacemaker fully finish processing of one membership change - elect
>>>>>>> new DC on a quorate partition, and do not try to take over dc role
>>>>>>> (or
>>>>>>> release it) on a non-quorate partition if quorate one exists, that
>>>>>>> problem could be gone.
>>>>>>
>>>>>> Non quorate partitions still have a DC.
>>>>>> They're just not supposed to do anything (depending on the value of
>>>>>> no-quorum-policy).
>>>>>
>>>>> I actually meant "do not try to take over dc role in a rejoined cluster
>>>>> (or release that role) if it was running on a non-quorate partition
>>>>> before rejoin if quorate one existed".
>>>>
>>>> All existing DC's give up the role and a new one is elected when two
>>>> partitions join.
>>>> So I'm unsure what you're referring to here :-)
>>>>
>>>>> Sorry for confusion. Not very
>>>>> natural wording again, but should be better.
>>>>>
>>>>> May be DC from non-quorate partition should just have lower priority to
>>>>> become DC when cluster rejoins and new election happen (does it?)?
>>>>
>>>> There is no bias towards past DCs in the election.
>>>
>>>  From what I understand, election result highly depends on nodes
>>> (pacemaker processes) uptime. And DC.old has a great chance to win an
>>> election, just because it won it before, and nothing changed in election
>>> parameters after that. Please fix me.
>>
>> Correct.  But its not getting an advantage because it was DC.
>
> But it could have it because it f.e. has greater uptime (and that actually
> was a reason it won previous elections, before split-brain).
> And then it can drop all cib modifications which happened in a quorate
> partition during split-brain. At least some messages in logs (you should
> have them) make me think so. If it is possible to avoid this - it would be
> great. So, from my PoV, one of two should happen
> * DC.old does not win
> * DC old wins and replaces its CIB with copy from DC.new
>
> Am I wrong here?

The CIB which is used depends not on which node was DC but which node
had CIB.latest.

>
> Vladislav
>
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