RE: EMI: Serious Problem PANIC: Too many concurrent allocations

> 
> Kannel currently has configuration variable maximum-queue-length. See 
> user-
> guide for details.
> 

Yes, but when this is triggered bb_smscconn_receive () logs the event and
returns -1. All the SMSC drivers except HTTP ignore the return code from
bb_smscconn_receive (). Therefore, the message is silently dropped from
the application and the SMSC point of view. This is IMHO a bad thing and
not something you could use in a production environment. I think a
better solution would be to;

* When possible, map the queue full event to an SMSC protocol error
indicating a temporary resource shortage; otherwise fail the message
with the most appropriate error code.

* Introduce a flow control admin. message to tell the SMS box (and any other
clients using the SMS box interface) to stop/start sending messages. The SMS
box could in turn signal to the various sendsms applications that a temporary
resource shortage event has occurred (HTTP 503 maybe ?)

* Use high and low watermark variables instead of maximum-queue-length. This prevents
thrashing around the maximum-queue-length value. A sort of SMS hysteresis curve :-).