Hi!
Thanks for your answers!
In my application there are a couple of servers as core members and a lot
of clients as spectators. The shoal framework is only used to decide which
member the clients should connect to, and this is group leader?s task
(weighted round robin). Making a spectator(client) group leader would in
this case letting a client decide which member all the other clients
should connect to and that doesn?t feel right. Am I using the framework in
a ?bad? way?
Date: Thu, 17 Apr 2008 10:55:46 -0700
From: Shreedhar Ganapathy <Shreedhar.Ganapathy_at_Sun.COM>
Content-type: multipart/alternative;
boundary="Boundary_(ID_K7t9fXcMXPa5oHOLCJQX4Q)"
Subject: [Shoal-Users] Unplanned shutdown of a spectator
Hi Viktor
Thanks for writing up these interesting questions. Hope my responses
clarify things for you.
Viktor.Claesson_at_ibs.se wrote:
>
> Hi!
> I have some servers as core members in a group. With an administration
> program I log on as a spectator. If this program makes an unplanned
> shutdown, it will still be in the group and the core nodes will try to
> send messages to the spectator node until the entire group has been
> shutdown.
If the spectator process leaves the group either abruptly or in a
planned shutdown, a view change is surely disseminated to all members
although a failure notification signal or planned shutdown signal is not
sent out to the core member clients by design.
> Is there any way to stop this?
The role of spectator was specifically designed to not impact core
members with its failure (unplanned shutdown). If the member is
continuing to stay in the view after its failure after the failure
verification timeouts have elapsed then that would be a bug.
Could you confirm and then file a bug report?
Also please let us know which version of Shoal you are using.
> Do you assume that a spectator node always makes a planned shutdown?
No not necessarily.
>
> Changing the admin program to become a core-member will of course
> solve this, but then I will run into another problem, it can become
> the group leader.
Will the Spectator becoming the group leader be of concern ? Do please
explain how it would affect your application as it will help us broaden
our view.
Nothing prevents a Spectator from becoming a group leader in Shoal as
group leadership is a group management with by the service provider
implementation. This does not necessarily have any bearing on the
consuming application. There are, of course, Shoal users who have
nmc``cnasked for APIs (which we have provided) that will give them
programmatic access to knowing who the group leader is but it is not the
intention to prevent Spectator's from becoming group leaders. When
spectator's fail or shutdown normally, another node is selected
deterministically to become the group leader.
Semantically, the Spectator's failure is not notified to GMS clients,
that's all. Internally, the Shoal service provider implementation does
recognize each member's failure and does appropriate view handling.
hth
Shreedhar
>
> Thanks in advance!
> Viktor