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List:       serusers
Subject:    [SR-Users] Re: Dialog Module: enable_dmq and multiple nodes update SAME profiles_with_value counter?
From:       Henning Westerholt via sr-users <sr-users () lists ! kamailio ! org>
Date:       2023-10-16 14:04:52
Message-ID: DB7PR07MB38827E1AE6F61345B01A8598BFD7A () DB7PR07MB3882 ! eurprd07 ! prod ! outlook ! com
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Hello,

some installations are using this distributed profile support also with writes from \
different places. It works ok for the usual application (like channel limiting, fraud \
mitigation etc..).

There is no locking in place, so if by some reasons a profile value will be updated \
from two servers the same time, it will probably not be the correct value saved in \
the profile. But usually this self-recovers, for example in the night due to the \
(dialog) timeout. If you are concerned with correctness against this kind of race \
conditions, you should think about using a real distributed datastore, like a \
clustered SQL/NOSQL database. 

Cheers,

Henning

-- 
Henning Westerholt – https://skalatan.de/blog/
Kamailio services – https://gilawa.com

> -----Original Message-----
> From: Benoit Panizzon via sr-users <sr-users@lists.kamailio.org>
> Sent: Montag, 16. Oktober 2023 15:28
> To: Kamailio (SER) - Users Mailing List <sr-users@lists.kamailio.org>
> Cc: Benoit Panizzon <benoit.panizzon@imp.ch>
> Subject: [SR-Users] Dialog Module: enable_dmq and multiple nodes update
> SAME profiles_with_value counter?
> 
> Hi Team
> 
> I'm still hunting down DMQ dialog issues.
> 
> https://www.kamailio.org/docs/modules/devel/modules/dialog.html#dialog.
> p.enable_dmq
> 
> Quote:
> "Notably, it is not possible to send in-dialog requests on any but the original
> proxy instance."
> 
> I make sure, that if a procied call (with same callID) is being redirected from
> anywhere, it is send to the came dialog aware kamailio instance it originated
> from. This seems to have fixed a lot of issues with dialogues getting corrupted.
> 
> The two main purposed we use dialog is:
> 
> * CDR
> * Channel Counting / Limiting
> 
> modparam("dialog", "profiles_with_value", "custprofilecounter");
> 
> Can a such profile WITH value be written from any node sharing dialog via
> DMQ or is this bound to cause troubes?
> 
> Example.
> 
> Two call get to same customer, but over two different nodes.
> 
> Node A is getting a call:
> 
> set_dlg_profile("custprofilecounter","Customer7664");
> get_profile_size("custprofilecounter","Customer7664","$var(busy_count)");
> 
> => $var(busy_count) is now 1.
> The profile is replicated to Node B and the value can be accessed there.
> 
> While Call on Node A is running, Node B is getting a call to same
> customer:
> 
> set_dlg_profile("custprofilecounter","Customer7664");
> get_profile_size("custprofilecounter","Customer7664","$var(busy_count)");
> 
> => $var(busy_count) is now 2 on Node B.
> 
> Is this value being replicated BACK to Node A where the profile counter
> originally was created?
> 
> As far as I have experienced, this is the case.
> 
> But what happens if the call on Node B is ending before the Call on Node A?
> Will the counter being decreased also correctly be replicated to Node A?
> 
> What happens the other way round?
> 
> What happens if both call end at the same time? Is a race condition possible,
> or is there some sort of locking to prevent this?
> 
> Can I use profiles_with_value the way I use them? Or is this bound to fail
> because it's not supported?
> 
> Mit freundlichen Grüssen
> 
> -Benoît Panizzon-
> --
> I m p r o W a r e   A G    -    Leiter Commerce Kunden
> ______________________________________________________
> 
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