[Spread-users] How to get list of all Groups and its connected members.

Murali Bommaku muralib at bsil.com
Fri Jul 23 09:27:28 EDT 2004


Hi,
Thanks for your answer. I apologize as this perticular question was not
listed in archives. Please if you have information regarding the subject,
kindly send me, it will be of great help.
Though its not directly supported by spread but i guess there must be
someway to get all list of groups and its members.

I repeat the question as bellow:

1.	I want to list all groups name (including joined group), which are
existed in Spread Daemon
(connected and other daemons).
2. 	I want to list all members for each group.

Regards,
Murali.

-----Original Message-----
From: Jonathan Stanton [mailto:jonathan at cnds.jhu.edu]
Sent: Tuesday, July 13, 2004 10:33 PM
To: Murali Bommaku
Cc: spread-users at lists.spread.org
Subject: Re: [Spread-users] How to get list of all Groups and its
connected members.


Hello,

You can find some discussion of this issue of listing all available groups
and members in the list archives. The short answer is that Spread does not
provide a way to directly query that currently. You can easily know the
list of members of a group you have joined (that is the membership
message) but if you do not join a group, Spread doesn't tell you the
members.

See below for more answers.

On Tue, Jul 13, 2004 at 11:41:17AM +0530, Murali Bommaku wrote:
> Hi,
> 	Is it possible to get list of all groups (including the joined group and
> other groups) and its connected members info from a valid group member?
> My requirements are as follows:
>
> I am using Spread 3.17.2, I connected to Spread and joined into a group. I
> wanted to do the following things:
>
> 1.	I want to list the other groups name, which are existed in Spread
Daemon
> (connected and other daemons).
> 2. 	I want to list all members for each group.

See above.

> 3.	I want to send a message only to specified member through Spread (both
> same group and differnt group).

Just send the message using the private group name of the targeted member
as the "destination" group. So if you want to send a message to a client
whose private name is "joe" who connected to the daemon running on machine
with name "a", then just send a SP_multicast to the group "#joe#a" which
is the private group name of that client. This 'unicast' message can be
done wither or not either client has joined any groups -- they just have
to have connected to a daemon. The easiest way to learn the private group
name of another client is to have them send you a message (as then the
'sender' field has the private group name). You can also 'guess' the name
as I did above because the names always follow a standard pattern
"#user#machine"


 > 4.	Is there anyway to send a message to other
group/group member?

Yes, Spread supports "open-group" semantics. Meaning any client can send a
message to any group (even if it has not joined the group).

> 5.	If I am disconnected due to spread daemon crash/termination then I want
> any nearest spread daemon automatically binds the members who are bind the
> just terminated spread daemon without losing any communication data.

This is not the way Spread works. The clients are responsible for any
fault-handling and failover because only the clients know the actual state
of the their application data. The Spread daemons do maintain their
internal state in the presense of failures and the set of daemons will
maintain all of hte groups -- however, the clients who were directly
connected to a failed daemon will have to reconnect to another daemon (or
wait for the failed daemon to restart) and then run a resynchronization
protocol for their application to catch up with clients and daemons who
did not fail.

In Spread 'clients' are in control of all of the connections and initiate
actions, the daemons just process messages requested by clients, so the
daemons can not initiate a failover of clients they are not connected to
as they do not know anything about their state.

Cheers,
Jonathan

--
-------------------------------------------------------
Jonathan R. Stanton         jonathan at cs.jhu.edu
Dept. of Computer Science
Johns Hopkins University
-------------------------------------------------------





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