[sr-dev] kamailio-ser integration - db modules

[Jan Janak]

The database API version 2 (originating from SER) is an evolved
version of the database API that Kamailio has (version 1), they both
share a common ancestor.

The main motivation for designing a new API was to make it possible to
integrate SER with non-SQL based databases. The general idea was that
SER would include an API that would enable it to execute general
queries on the database server. Any results those queries produce
would get converted into AVPs. SER modules that depend on data
obtained from the database would then work primarily with those AVPs.
You could also process those AVPs directly in the configuration file
in the routing logic.

In theory this enables the integration of SER with in-memory and
no-SQL based databases. I have tested this with LDAP (hence the
generic LDAP database driver), Cassandra, and other (proprietary)
database engines. One could also implement RADIUS support in form of a
database connector via this API, but I never found the time to do
that.

The version 2 of the database API is, unfortunately, not backwards
compatible with version 1. That's because version 1 assumes that all
database queries are directly mapped to corresponding SQL statements.
Version 2 is a bit more general and does not assume SQL.

Although we also did a number of changes to the database schema used
by SER around the same time, those schema changes are not related to
the new database API. Version 2 of the database API does not require
schema changes per se and it should work fine with the database schema
used by Kamailio.

Somewhere in the process of changing the database code I also added
support for pre-compiled statements to the MySQL connector module, in
fact the module uses them by default for all database queries. I
thought this might improve performance of the MySQL connector module
(which it does under certain circumstances), but in practice it only
makes things more complicated. Properly configured SQL query cache on
the database server works even better in terms of performance.

-Jan

On Thu, Dec 20, 2012 at 11:38 AM, Ovidiu Sas <osas at voipembedded.com> wrote:
> On Thu, Dec 20, 2012 at 11:20 AM, Daniel-Constantin Mierla
> <miconda at gmail.com> wrote:
>>> What's the difference between the db1 and db2 interface?
>>
>> It is not the case here, modules_k/ldap does not have any relation to
>> database interface.
>
>
> Any database module db_[DatabaseType] implements an API.
> SER was using one API and opensips/kamailio a different API (and
> therefore today we have version 1 and 2).
> All db modules in the stable release are supporting both APIs.
> The new db ldap module has support only for the SER API version.
> The API is documented in each lib/srdb[1|]/*.h header files.
>
> The ldap module from ser is completely different than ldap module from
> kamailio (despite the fact that both are using the same name).
> It's the same with the dialog module.  Check the README file for each.
>
> Hope this brings a little bit of light :)
>
>
> -ovidiu
>
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