[Spread-users] wildchar subscriptions

[Jonathan Stanton]

It will depend on what semantics you want this "wildcard" member of the
groups to have. 

If you do NOT want the wildcard member to have the same
strong semantics as the other group members (if they can not have the
EVS guarantees and the other members of the group will NOT see them as a
member) then you can do this with a not too hard hack to groups.c. You
just make a "magic" group called "wildcard" and anyone who is in that
group gets a copy of every message whose targets are calculated by
G_analize_groups(). So you basically add the sessions associated with
the members of the wildcard group to the target_sessions list at the
last moment.

Now, to be clear this not only doesn't guarantee the normal
fault-tolerance properties, but it also will have problems with
flow-control as this member can easily become overwhelmed.

If you want to preserve the strong semantics, and really have the member
joined in all of the groups, that will be a much more costly operation
(as they will really have to be added to every group, and they will get
a LOT of membership messages) and some special checks will have to be
added to make sure they are added to any new groups that also are
created by any client. I'd have to think more about this to see if there
are any subtle problems.

Jonathan

On Wed, Apr 30, 2003 at 11:17:40AM +0200, christian.wohanka at systemagmbh.de wrote:
> Hello list,
> 
> has anybody tried to implement something like wildchar subscriptions, e.g.
> a client joins a group "*" and will receive the messages of all groups
> available
> in the whole Spread network?
> 
> Maybe someone can tell me if such a functionality is in principle possible
> and
> how much work it will take approximately (1 day, 5 months or ages) to
> implement such a thing.
> 
> 
> Thanks in advance
> 
> Christian
> 
> 
> 
> 
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-- 
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Jonathan R. Stanton         jonathan at cs.jhu.edu
Dept. of Computer Science   
Johns Hopkins University    
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