[infinispan-dev] dealing with cluster partitions (design wiki) WAS ( design for cluster events (wiki page))

[Radim Vansa]

On 10/30/2013 08:46 PM, Mircea Markus wrote:
> On Oct 30, 2013, at 7:28 PM, William Burns <mudokonman at gmail.com> wrote:
>
>> Since it seems I can't comment on the wiki itself, I am just replying here.
>>
>> I wonder if the third option 'Primary partition' is desirable.  I
>> think availability in some cases would be harmed more than we would
>> like.
>>
>> Lets say you have a 5 node cluster where 3 of the nodes are behind the
>> same router and the remaining 2 are behind a different one.  If the
>> router crashes, power loss etc. for the 3 and are no longer
>> addressable you have your 2 partitions (possibly 1 or even 4).  When
>> this occurs the other 2 nodes would go into read only mode since they
>> lost the quorum check.
> agreed.
>
>>   But the 3 nodes that are "writable" can't be
>> accessed any longer and thus no writes can be performed on the
>> cluster.  It seems we would still want to allow writes to provide as
>> high of availability as possible.
> we actually don't take the decision for the user but to plug in his own PartitionHandlingStrategy to make a wiser decision based on their network specifics.
> The quorum approach written there is just a suggestion, I'll make that clearer.
>
>> Also if we did have read only, what criteria would cause those nodes
>> to be writeable again?
> Changing the availability status is possible through JMX, so either manual intervention or some MergeListeners that do that automatically.

You should probably outline the MergeListeners on wiki as well. I 
believe that automatic merge is highly desirable, because for example 
long GC may cause partition more likely than network failure - and you 
don't want to require some monkey pushing JMX after every long GC.

Radim

>
>>   There is no guarantee when the other nodes
>> will ever come back up or if there will ever be additional ones
>> anytime soon.
>>
>> - Will
>>> [1] https://github.com/infinispan/infinispan/wiki/Handling-cluster-partitions
> Cheers,


-- 
Radim Vansa <rvansa at redhat.com>
JBoss DataGrid QA