[sr-dev] usrloc and db only mode

[Daniel-Constantin Mierla]

Hello,

following some discussions on github issues, mailing list and irc
recently, I am opening a topic and see if we can get something to
accommodate the needs out there at the best for everyone.

These are more in the context with the increase of sizes for
deployments, but also having the option to use a no-sql, some internal
bits of usrloc may need tunings.

The points to be considered:
1) discovering what is the server that wrote the record
2) efficiently getting the records that require nat keepalive

The two are sometime related, but not necessary always.

Victor Seva on irc channel was saying that is planning to propose a
patch for 1), relying on socket value in the location table. The use
case presented was many servers saving and looking up the records in the
same table, but fetch only the records written by current instance for
sending keepalives. It makes sense not send keepalives from all
instances, for load as well and bandwidth considerations. This could
work relying on local socket, but I am not sure how efficient will be
when listening on many sockets (different ips, but also different ports
or protocols - ipv4/6, tcp, tls, udp -- all add sockets).

On 2), it's being for a while on my list to review, as the module uses
custom sql queries (or even functions) to be able to match the the
records for sending keepalives -- it does matching with bitwise
operations to see if flags for nat are set. That doesn't work with
no-sql databases (including db_text, db_mongodb and I expect
db_cassandra). Even for sql, that kind of query is not efficient,
especially when dealing with a large amount of records.

The solutions that came in my mind for now:

- for 1) -- add the server_id as a new column in the location table. It
was pointed to be that ser location had it. This will turn a query
matching on many socket-representation strings to one expression done on
an integer. The value for server_id can be set via the core parameter
with the same name.

- for 2) -- add a new column 'keepalive' to be set internally by the
module to 1 if any of the flags for sending keepalive was set. Then the
query to fetch it will just use a match on it, rather that bitwise
operations in the match expression. Furthermore, this can be set to a
different value when enabling the keepalive partitioning (ie., sending
keepalives from different timer processes, each doing for a part of
natted users) - right now, for the db only mode, the selection is done
by column id % (number of keepalive processes).

Opinions, improvements, other proposals?

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Kamailio World Conference, May 27-29, 2015
Berlin, Germany - http://www.kamailioworld.com