[asterisk-users] Scaling/Loadbalancing a Call Center and Redundancy
stotaro at asteriskhelpdesk.com
Fri Sep 15 19:34:29 MST 2006
I have been tossing around some ideas about scaling a call center with
load balancing and redundancy and would like the comunities input,
thoughts, criticism and anything anyone wants to toss in.
The most evident thing is to start with beefy servers and only run procs
that are required. All of the TDM boxes run stripped down versions of
Linux and Asterisk, they just take the call from the PRIs and convert
them to SIP, everything stays ulaw end to end.
*Shared queues across multiple servers would be ideal*. I don't think
it is possible in asterisk, as is. Maybe DUNDI could be useful but I am
not up to speed on it enough to really know.
I was toying with a concept of a DB server tracking the number of calls
to queue(s), number of agents logged into the queue(s). Some agents
will be logged into multiple queues and providing the logic to a series
of Asterisk servers. Calls could be made to the db to determine which
queue/server to route the call to. In this situation, duplicate queues
would exist on several servers, so balancing would work somewhat if the
DB made the selection on which box to route the call to and which box an
agent should log into. FastAGI and the manager interface will provide
the routing and DB updates.
Another thought was to have one central server with all of the queues
and agents, then somehow the central server would cause a "recording/CDR
server" to send re-invites to the two SIP endpoints so that the call/RTP
stream is moved to another asterisk server which would record the call
and keep the CDR info. Again, this would be done with a DB to decide
which asterisk (recording/CDR) box has the lightest load. It would take
the burden of maintaining the call from the "Queue" server. I/O is the
first bottleneck in scaling when you record each and every call.
Would it be difficult to have asterisk send two SIP endpoints re-invites
and then bridge the call? Then it is just a matter of the "Queue"
server checking the DB which recording/CDR server the call should go to
and send it a message to re-invite and bridge the endpoints. A transfer
to a meetme is another possiblility but I want the "Queue" server out of
Has anybody else thought through the best way to scale something like
this. I have a DS3 and will be using all of the channels in the
semi-near future. I need to come up with a workable plan before then.
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