Hello,
On 2/1/11 8:18 PM, Timo Reimann wrote:
[...]
Apart from this very minimum CDR content, however, one can think of a
number of CDR fields that cannot be filled easily. For instance, caller
identity isn't always contained in the From header (think of CLIR calls)
but need to be determined from other headers depending on the type of
call, possibly even involving a database lookup.
From header URI is not accounted automatically, you can specify any
variable that can contain caller id as you need (e.g., it can be an AVP
that you previously set for in config) -- see *_extra parameters of acc
module.
That's why I'd like to
provide a way to pass additional, CDR-specific data from the
configuration file to the dialog structure associated with the call.
When the dialog is about to terminate, the extended acc module would
make sure that the added CDR data associated to the dialog is included
in the CDR.
Not sure what you mean here with "acc module will make sure ...", but I
hope is not going to be cross reference/dependency, so that acc has to
walk through dlg structures.
This way, users may define CDR fields to their personal
needs from the configuration file in a flexible manner.
In order to accomplish this, the dialog module would need to be extended
such that dialog-specific data may be stored for the duration of a
dialog (which is not possible to this day AFAICS).
Carsen committed some code in this regard in his IMS branch, as I could
see from commit log, check:
http://lists.sip-router.org/pipermail/sr-dev/2011-January/010197.html
Probably it will be merged sometime in the near future.
A new setter function
attached to the dialog interface (struct dlg_binds) could accept a
simple key/value pair for storage purposes. Exporting this function to
the configuration file and accompanying it with a corresponding getter
function will ensure that dialog-specific data may be written and read
generically. Thus, improvements to the dialog module may be leveraged
not just for CDR-accounting purposes.
Regarding the acc module, a couple of new features need to be
implemented: First, the introduction of another module parameter called
something like "cdr_fields" that comprises the set of key names
designated for CDR inclusion. Hence, a line like
modparam("acc", "cdr_fields", "caller, callee, foo, bar")
The db_extra has the format of 'key=variable', where the 'key' is the db
column name and the 'variable' is the name of PV holding the value to be
stored. I think the format is better than just providing the names of
the dialog keys.
would require Kamailio configurators to store dialog-specific values for
the keys "caller", "callee", "foo", and "bar", respectively, during call
processing. The values will be fed to the dialog structure employing the
new dialog store function explained above.
I think exporting anything related to dialog via PV and fetching them
like this will be better from point of view of cross-relationships.
Second, when the acc module is in CDR mode, dialogs shall be tracked
from creation to termination using dialog callbacks. On termination of a
dialog, values from keys referenced in the "cdr_fields" parameter will
be fetched from the terminating dialog structure and associated with the
new, fresh CDR.
Third, the CDR is persisted to either log file, database, or both.
If this new thing is not going to support what acc module API has for
backends (radius is missing), then will not make sense to tie the two.
dialog module can do its accounting alone.
Note that my approach would not touch the existing acc module
functionality: CDR mode is supposed to be working in addition to
transaction-based accounting as people will likely want to keep
transaction logs for debugging or similar needs. A flag would enable and
disable CDR generation at will. I have not fully investigated
re-usability possibilities but believe that acc's persistence functions
may be taken advantage of by the new CDR-producing parts as well.
That's it with regards to the basic mode of operation. I am also
thinking of having a few other features, such as using a switch to set
the call start time to the moment the ACK or OK is seen instead of the
INVITE (because users shouldn't be billed for call setup times).
Looking forward to seeing your feedback on this proposal.
As general observation, there are some modules (I mainly think about
presence) that have cross references/dependencies that should be avoided
normally, and planned to clean it up already. It is not good to have A
uses/needs B and B uses/needs A
Regarding db accounting:
- I have in my todo list the plan to enhance acc to export a functions
like acc_start() and acc_stop(), with the goal of storing the initial
record for start of the call (acc_start() for INVITE) then at the end of
the call (BYE) acc_stop() will just set extra details (end time,
duration, etc)
- practically then dialog module can call acc_start() and acc_stop() via
some inter-module api. The benefit is that even sip server crashes
suddently, there is an acc start event to indicate a call
- such functionality is independent of dlg module or any new call
tracking extension in the future, also writing full CDR can be achieved
from config file by tracking INVITE and BYE, calling
acc_start()/acc_stop() from cfg
Therefore if I would do it:
- enhance acc module to export via cfg exports and inter-module api
three functions:
- acc_start() - write the initial call record at start
- acc_stop() - update the call record at stop, based on a matching
condition specified as parameter
- acc_cdr() - write a full CDR
Data to be written in db (or other backend) is going to be taken from
PVs, independent of who (cfg, dialog, or other module) is calling the
function, specified in a similar form like db_extra.
First two functions will work for db only. Third can work also without
dialog, e.g., I can store the start of a call, a.s.o. in hash table and
get it at BYE time to build the full cdr.
Your needs seem to fit in 3, so if you can (wish to) work on that only,
I will take care of the first two when I can.
Cheers,
Daniel
--
Daniel-Constantin Mierla
http://www.asipto.com
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