Hello,
2015-11-13 16:08:20 [DbManager::connectFallbackLogic] ERR: exception 'Exception' with message 'failed to connect to sphinx2' in /opt/kaltura/app/infra/log/KalturaLog.php:83
Indicates that the value you have in /opt/kaltura/app/configurations/db.ini for sphinx2.connection.dsn is invalid.
This is OK assuming you only have one Sphinx node, which is fine in the event you are running a single server.
You can ignore the error in such a case or else, you can just set it to
sphinx2.connection.dsn = "mysql:host=127.0.0.1;port=9312;"
In the event you do have a cluster and two sphinx nodes, you should check why the second one is not available.