[asterisk-dev] device_state distribution issues

[Russell Bryant]

On Mon, 2010-11-08 at 10:56 -0600, Kevin P. Fleming wrote:
> On 11/08/2010 06:12 AM, Klaus Darilion wrote:
> 
> > Does Asterisk keep proper state of remote devices (e.g. with a call 
> > timeout)? If yes, then it is a bug. If no - then it would explain this 
> > behavior but IMO would be a serious limitation.
> 
> I suspect you may be trying to do something that is not yet supported:
> to my knowledge, the device state distribution that exists today is to
> allow a device that is managed by *one* server to be visible to other
> servers, so they can make decisions based on its state. It does not
> support *multi-master* mode, where multiple servers are involved in
> computing the state of a single device. For that to be possible, there
> would have to be some 'owner' of the device to consolidate the
> information from the servers involved.

In the case of res_ais, it works by having every server report state
changes that occur on that server.  The result is that each server has
an internal table of the state of each device from the perspective on
each server involved.  When the state changes on _any_ server, it then
looks at the last known state of that device on all servers and
determines an overall state.  So, based on that, this is supposed to
work.

The way this works is that each event is tagged with a server ID
(referred to as an entity ID, or EID).  From a quick look at the XMPP
implementation, it appears that the server ID is not being propagated.
So, the failure you are seeing is not ideal (a bug actually, please
report it), but it is the expected behavior right now.

The XMPP distributed device state code needs to be updated such that the
EID information element is included in state changes that it sends out
such that its behavior matches that of the AIS implementation.

-- 
Russell Bryant
Digium, Inc.  |  Engineering Manager, Open Source Software
445 Jan Davis Drive NW   -    Huntsville, AL 35806  -  USA
jabber: rbryant at digium.com    -=-    skype: russell-bryant
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