[OpenSIPS-Users] get_dynamic_lock best practice

[Cinthia Leung]

Hello all,

We're trying to use get_dynamic_lock as a solution to a race condition.
OpenSIPS receives an in-dialog INVITE and UPDATE almost at the same time
from a UAS and passes both to the SIP client immediately.  The client
responds to whichever one arrives first and sends a SIP 500 to the second
packet.

I know we should look into fixing this behavior in the UAS.  But this
wonderful cfgutil feature looks like something that may help us in the
meanwhile.  We call get_dynamic_lock for the first packet in in-dialog
route.  release_dynamic_lock is called when we receive a final response,
which should not take long because there's no human interaction involved.
And then the second packet gets the lock.

We have since learned that this approach does not work well when there's
network latency that causes the UAS to retranx, as you can imagine.  We are
planning to use t_check_trans() before calling get_lock.  At the same time
we're wondering if there's a way to keep track of these locks, potentially
periodically purge them as needed.

If you have any other ideas on how to solve our originally problem then
even better.

TYVMIA!


Cindy
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