Hi all,
I'd like to bring forward a proposal for creating CDRs (Call Data Records) from Kamailio by means of extending both acc and dialog modules. Feedback is very welcome.
So far, CDR generation requires post-processing of log entries created by the (transaction-based) acc module or some other means. Looking at OpenSIPS (which is already capable of producing CDRs), my idea is to copy the basic notion of tracking dialogs for to-be-accounted calls and log a proper CDR on termination. Creating basic CDRs including start time, end time, and call duration can be accomplished quite easily this way.
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. 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. 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). 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")
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.
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.
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.
Cheers,
--Timo
Hello,
On 2/1/11 8:18 PM, Timo Reimann wrote:
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.
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.
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.
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.
I think exporting anything related to dialog via PV and fetching them like this will be better from point of view of cross-relationships.
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.
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
Hey Daniel,
On 01.02.2011 21:15, Daniel-Constantin Mierla wrote:
I initially thought about having a cdr_extra parameter similar to log_extra. However, I see a problem with AVPs which live in single transactions to work with dialogs that span multiple transactions.
Say you want to have a CDR field that contains combined or concatenated data from multiple transactions, e.g., all Kamailio flags set in the INVITE, ACK, and BYE transaction. How could that be accomplished with a log_extra-like module parameter? At what times would AVP be parsed? IMHO, you will need to keep such data per dialog which is why I came up with the idea of storing CDR-specific data in the dialog.
If I get you right, by cross reference/dependency you mean that A requires B and vice versa, i.e., cyclic dependency. I do not intend to let that happen.
Instead, the acc module would use getter functions attached to the dialog interface (which is what I mean by "acc module will make sure"). dialog would never touch the acc module or even know about the fact that the acc module is using it.
Missed that one. Will take a look at it.
See my comment above for why binding PVs to CDR fields does not seem appropriate in this case.
Of course, I would want to take advantage of acc's existing backend connectors. There's no need to re-invent the wheel, acc will still be responsible for writing out CDRs; the difference is that a few additional calls to a well-defined dialog interface will be used in order to collect the data that constitute the CDR.
Regarding server crashes/restarts, instead of persisting events ASAP via acc module I would recommend using dialog's existing feature to store dialog data in a database. That way, every piece of CDR-specific data stored in dialogs in my approach will be saved automatically (as governed by dialog module configuration), and there will be no need to produce partial CDRs in the first place.
Tracking INVITE and BYE messages from the config file may not be enough if you want to create CDRs for failed calls too, e.g., 408/487. They may not be relevant for billing but having them in a CDR database may still be desired.
Does your approach allow automatic CDR generation, or will you need to call these acc_* functions explicitly? I'd prefer to have automatic CDR persisting, similar to how transaction-based accounting in the current acc module works.
Where would you maintain that hash table containing the call start time and similar data if you do not seek to use the dialog module? Such data seems to be naturally associated to a dialog, so my impression is that it should be kept there too, i.e., in the dialog module.
Cheers,
--Timo
Hello,
On 2/2/11 12:52 PM, Timo Reimann wrote:
well, some of the avps are transaction persistent, but there are also global avps which are available as long as kamailio runs. None of these should be used, I gave avp just as generic PV example. The idea was to make new PV available with the data stored by dlg module.
It is not about where the data is store, it is about how acc accesses that data. I would like to avoid acc module being aware of dialog module internals. In the future might be different call tracking extensions, I don't want to change acc each time.
That's why we have PVs, if I want to record something from XYZ module, acc is not going to be changed and understand what xyz stores internally, but XYZ should export some PVs for that.
For example, if I want to record something from a HTABLE, there is nothing to do in acc, just specify $sht(x=>mykey) to some of acc parameters.
But then acc has to know the dialog internals, what the getter function will return and how to access those structures. PV framework is exactly the same, but available for all components/modules, no need to develop specif ones each time.
With your solution, dialog module has to know acc api to call the recording function, and acc has to know dialog module to know its exported structures. This is cross dependency imo.
I still don't see your point.
What will happen if a new call tracking module will be available, should acc be changed again?
What stops tracking these replies in the cfg?
Anyhow, I think you divert from the initial goal. If you just break the message in pieces and reply on each word will lose the meaning of the entire content. I presented my plans above and below I added acc_cdr() that seems to suit your needs.
The hash table module (htable) keeps the data in shared memory. It is a generic container, so you can store anything there. dialog module is just an automatic call tracker, handling sip messages passing through kamailio. Most of that can be done from config file. Internally, dialog module has also a hash table. Also, I can track active calls using a db table (in memory or not for speed), with a timer process (rtimer module) to handle missing BYEs, and so there could be other options to track dialogs. My point here is that acc should be independent of all these potential options available now or added in the future.
You additions to dialog module can export the new stored data inside dialog via some PV, e.g.,
$dlgacc(caller), $dlgacc(callee), $dlgacc(duration), a.s.o.
dialog module will call acc_cdr() when the call ended, making sure the PVs are properly available at that time.
Cheers, Daniel
On 02.02.2011 14:03, Daniel-Constantin Mierla wrote:
Ok, so instead of providing getter/setter functions, let's use PVs. However, users will have varying needs regarding the to-be-defined CDR fields next to the canonical ones (start time, end time, duration, etc.). We, for example, use a rather large number of fields, many of them being too specific for general integration into upstream Kamailio. That's why I would rather see a way to dynamically specify CDR fields. Carsten's new code would be the right approach to do this, right? His dlg_var PV takes arbitrary key/value pairs which looks just like what is needed.
Agreed, let's use PVs. If you think of Carsten's new dlg_var PV, it's basically just a way to get/set arbitrary values; so I suppose this is what I should have expressed.
I think this point shows the major difference between our solutions: My approach doesn't make the dialog module call the recording function. Instead, the recording function is called by the acc module as soon as the dialog terminates where call termination can is observed by means of using dialog callbacks. (Sorry, I should have possibly mentioned the words "dialog callback" before.)
Therefore, module dependency is unidirectional: acc registers for some dialog callbacks and, upon execution of a callback, records the CDR.
I am not completely convinced that call tracking is such a flexible thing even though you gave a few examples below. A call is pretty much a dialog, and proper tracking of a dialog should be dialog module's job.
Moreover, I believe your approach has some dependency issues as well -- see my comment at the very end of this mail.
You can do it, but for a large config file with many different paths, it's easy to miss a spot where you should have added a call to acc_stop(). On the contrary, if recording happens automatically when the call ends, you don't have to deal with any manual work.
Maybe I got you wrong but my understanding is that acc_start() records one part of a CDR (start time, etc.) when the INVITE is routed while acc_stop() finishes it off (end time, duration, etc.) on reception of the BYE. I was trying to stress that a single call to the recording function is likely preferred (at least by me), which acc_cdr() seems to accomplish.
If you call an acc module-provided method from the dialog module, you face a similar independence problem: Should accounting functionality ever be changed or replaced of by another module, then you'd need to change the dialog implementation as well.
There's a conceptual issue related to the given usage relationship as well: If component A requires B to implement a particular functionality, A should use B. Having the dialog module trigger the recording function puts this concept upside down -- CDR accounting isn't needed by dialog tracking, it's the other way around.
Cheers,
--Timo
Hi,
The functionality for storing additional data for a dialog is like this:
$dlg_var(ecscf_server) = ‘sip:ecscf.ng-voice.com’; xlog(“Emergency CSCF is $dlg_var(ecscf_server)\n”);
However, it might be worth noting, that i haven't added bindings to the dialog-API and that the Pseudo-Variable currently only supports Strings. I think, my branch needs to exists a little longer, since the changes take quite a lot of time. I am currently doing a lot of cleanup where many methods get obsolete; so i do not want to add docs for later obsolete methods and parameters. I think i will need to check, how i can easily just merge some commits instead of all of them (any hints welcome, otherwise i will ask google...).
Kind regards, Carsten
2011/2/2 Timo Reimann timo.reimann@1und1.de:
Hey Carsten,
On 07.02.2011 12:04, Carsten Bock wrote:
For CDR generation purposes, I wouldn't need any additional dialog API bindings. The PV interface should suffice as Daniel and I have concluded on the mailing-list and at FOSDEM.
What aspects of your branch do you plan to change in the future? Would that affect the PV interface as well?
If you can provide a rough plan in order for me to consider whether the changes may affect my CDR approach I'd be very glad.
Ideally, if the dialog data storage functionality is somewhat complete, we may consider putting it into the master branch prior to any outstanding changes in your branch.
Let me know if there's anything I can do.
Cheers,
--Timo
-
Carsten Bock -
Daniel-Constantin Mierla -
Timo Reimann