[asterisk-dev] device_state distribution issues

[Klaus Darilion]

Russell Bryant wrote:
> 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.

Ok. I will try to find some time to test with AIS.

> 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.

Here is the trace of an event sent from Asterisk to the XMPP server:


<iq to='pubsub.armani.labs.nic.at' 
from='armani_asterisk at armani.labs.nic.at/asterisk' type='set' id='aaald'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
   <publish node='device_state'>
    <item id='SIP/klaus0'>
     <state xmlns='http://asterisk.org' 
eid='00:16:3e:e4:77:12'>INUSE</state>
    </item>
   </publish>
  </pubsub>
</iq>

As you see there is an eid transmitted. If I can read the trace 
correctly it seems that the published event is sent from the XMPP server 
to all subscribed Asterisk server - even the one which published the event.

Takeing a look at the code shows that the eid is used in res_jabber, at 
least to filter out the own events:

aji_handle_pubsub_event(...) {
   ...
   ast_str_to_eid(&pubsub_eid, iks_find_attrib(item_content, "eid"));
   if (!ast_eid_cmp(&ast_eid_default, &pubsub_eid)) {
     ast_log(LOG_DEBUG, "Returning here, eid of incoming event matches 
ours!\n");
     return IKS_FILTER_EAT;
   }
   ...

> 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.

As shown above it is already sent out and used for filtering, probably 
it misses keeping of the remote state.

regards
Klaus