MMTel Conference View Update

The feature first checks whether the ConferenceHasEnded flag has been raised by the MMTel Conference feature. If so, the feature then checks to see whether a ConferenceViewRemovalDelay config property has been specified. This states the number of milliseconds to wait after observing the ConferenceHasEnded flag before cleaning up the conference view state in Cassandra. This ensures all conference subscriptions can end and be cleaned up prior to the conference view state. Therefore, if ConferenceViewRemovalDelay is non-zero, the feature will wait the allocated time before cleaning up, otherwise it will initiate cleanup procedures immediately.

Once the feature has established that either the conference has not ended or that it is ready to clean up the conference view state, it then determines the actions necessary to achieve this. The feature reads the actual conference state from sessionState fields defined in the MMTel Conference library and uses this to form the target state which the view state in Cassandra should reflect. The feature then reads the confirmed state, that is, the conference view state currently stored in Cassandra. However, as opposed to reading this from Cassandra directly, the feature reads this from a local session state field that it maintains and updates only on receipt of a successful write query from Cassandra. The feature then checks there are no other pending queries, and whether the target and confirmed states are different. If so, it then initiates an update to the Cassandra view state and signals that the feature is waiting.

When the feature receives a success response on a query, it updates the local view state according to the contents of the successful query. Following this, it re-checks that the actual conference state matches the view state in Cassandra. If it does not match it will then initiate another update to the Cassandra view state and signal that the feature is waiting. Otherwise, if it does match, it will signal that the feature has finished.

When the feature receives an error response on a query, it finishes without updating the Cassandra view state nor its local view state. Instead, any mismatch between the actual conference state and Cassandra will be resolved following the next invocation of the MMTel Conference feature. This is in conjunction with any other state changes that may have occurred during this time.

In conjuntion with being invoked after the MMTel Conference feature, the MMTel Conference View Update feature also reads session state written by the MMTel Conference feature to determine the current conference view state. This includes the JoinedParticipants field which returns a MMTelCONFConnectionRequestQueue instance, a collection of MMTelCONFConnectionRequest objects that describe each participant connection to the conference. The feature also reads the ConferenceID and ConferenceHasEnded session state fields directly for retrieving data common to all participants in the conference.

The MMTel Conference View Update feature does not write any data that is used by the MMTel Conference feature. All session state fields written by this feature are only used internally.

This feature is exclusively responsible for keeping an up-to-date representation of the conference state in Cassandra. It, therefore, only writes data to Cassandra. This data continues to be made available for the duration of the conference solely for consumption by the MMTel Conference Subscription feature. The MMTel Conference Subscription feature uses this data to inform UE subscribed to the conference of the current conference state via sip NOTIFY transactions.