[SR-Users] dialog module: in-early-dialog requests / race conditions

[Timo Reimann]

Hi,


Ovidiu Sas wrote:
> On Tue, Jun 22, 2010 at 12:27 PM, Timo Reimann <timo.reimann at 1und1.de> wrote:
>> 2.) Various race conditions may generate log messages such as following
>> when DID mode is enabled:
>>
>> WARNING:dialog:dlg_onroute: unable to find dialog for <REQUEST TYPE>
>> with route param 'faf.f69e7b4' [4015:79161711]
>>
>> Observed REQUEST TYPEs at our site were "BYE" when BYE requests were
>> transmitted by both caller and callee at roughly the same time due to
>> user behavior; and "PRACK" when a PRACK was received by the UAS after a
>> 486 (Busy Here)/ACK pair of messages was already exchanged between the
>> UAS and the proxy. In both cases, the associated dialog had already been
>> destroyed when another request was received.
>>
>> My suggestion is to lower the log level for this kind of message because
>> it can simply happen too often but doesn't affect proper dialog handling.
> 
> The proper fix here would be to extend the lifetime of a dialog in
> deleted state and absorb any late in-dialog requests.
> If we just lower the log level, we don't know if it's a valid warning
> log or a bogus one.

I've been wondering how to achieve this.

AFAICS, the current implementation removes dialog entries right after
the moment the final request/response pair was seen. In order to prolong
a dying dialog's lifetime, I see two possibilities: Use some
time-triggered function that delays dialog deletion for a short period
of time; or, couple dialog deletion to the deletion of the final
transaction, i.e., the one were dialog state transitions to
DLG_STATE_DELETED. Personally, I prefer the latter approach since it
would quite elegantly re-use the transaction layer's timer.


Cheers,

--Timo