3 Feb
2011
3 Feb
'11
3:05 a.m.
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.
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.
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.
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.
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.
What will happen if a new call tracking module will be available, should
acc be changed again?
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.
What stops
tracking these replies in the cfg?
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.
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.
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
On 01.02.2011
21:15, Daniel-Constantin Mierla 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. On 2/1/11 8:18 PM, Timo Reimann 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. [...]
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. 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 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.
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. - 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
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. 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.
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.
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.
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.