[infinispan-dev] design for cluster events (wiki page)

[Mircea Markus]

On Oct 31, 2013, at 3:45 PM, Dennis Reed <dereed at redhat.com> wrote:

> On 10/31/2013 02:18 AM, Bela Ban wrote:
>> 
>>> Also if we did have read only, what criteria would cause those nodes
>>> to be writeable again?
>> Once you become the primary partition, e.g. when a view is received
>> where view.size() >= N where N is a predefined threshold. Can be
>> different, as long as it is deterministic.
>> 
>>> There is no guarantee when the other nodes
>>> will ever come back up or if there will ever be additional ones anytime soon.
>> If a system picks the Primary Partition approach, then it can become
>> completely inaccessible (read-only). In this case, I envisage that a
>> sysadmin will be notified, who can then start additional nodes for the
>> system to acquire primary partition and become accessible again.
> 
> There should be a way to manually modify the primary partition status.
> So if the admin knows the nodes will never return, they can manually 
> enable the partition.

The status will be exposed through JMX at any point, disregarding if there's a split brain going on or not.

> 
> Also, the PartitionContext should know whether the nodes left normally 
> or not.
> If you have 5 nodes in a cluster, and you shut down 3 of them, you'll 
> want the remaining two to remain available.
> But if there was a network partition, you wouldn't.  So it needs to know 
> the difference.

very good point again.
Thank you Dennis!

Cheers,
-- 
Mircea Markus
Infinispan lead (www.infinispan.org)