Some additional comments :
On 5/3/10 11:19 AM, Joseph Fialli wrote:
>
>
> On 5/3/10 2:05 PM, Ramakrishnan, Lakshmanan [Tech] wrote:
>> Hi,
>> I am new to Shoal. So pardon my ignorance.
>> We are trying to create a cluster for our application and came across
>> Shoal. Here is a simplified requirement. We have many instances of
>> the application running one of them will be a leader. When this
>> instance fails, another instance will become the leader.
> See GroupLeadershipNotificationSignal javadoc
> <https://shoal.dev.java.net/nonav/docs/api/com/sun/enterprise/ee/cms/core/GroupLeadershipNotificationSignal.html>
> for documentation on GMS notification that occurs when a group
> leadership change occurs.
> Within Shoal gms workspace, check out
> tests/com/sun/enterprise/shoal/groupleadertest/GroupLeadershipNotificationTest.java
> for an example
> on how one can register a callback for GroupLeadershipNotification
> from GMS system.
>
>> Can this be implemented in Shoal? I see that there are 2 types of
>> membership in Shoal ie spectator and core. Is there a way
>> programmatically change the membership from spectator to core (and
>> vice versa)?
> One specifies whether a member is CORE or SPECTATOR at configuration
> time.
> It is a property passed into GMSFactory.startGMSModule(...).
> <https://shoal.dev.java.net/nonav/docs/api/com/sun/enterprise/ee/cms/core/GMSFactory.html#startGMSModule%28java.lang.String,%20java.lang.String,%20com.sun.enterprise.ee.cms.core.GroupManagementService.MemberType,%20java.util.Properties%29>
By extension, in order to change the membership type from Spectator to
Core or vice versa, the member will need to leave and rejoin the group
as the other member type as it is curently implemented.
Also, Spectators can become Group Leaders - there is nothing preventing
a Spectator from becoming a group leader - this is due to the fact the
various group communication libraries have their own way to look at
member coordinators independent of the way Shoal sets member types. A
Spectator is one whose failure is not material to the group members.
hth
Shreedhar
>
> -Joe Fialli
>> Thanks
>> Lakshmanan