DDS15 — Communication Status changes for multiple events

Plain Communication Status structures may undergo multiple changes between the time the first event occurs and when the application reads/resets the Plain Communication Status. This results in loss of important data that DDS should make available to the application. It is more likely to occur when using the WaitSet/StatusCondition mechanism instead of Listeners, but may occur with Listeners depending on how the implementation determines when to invoke the Listener.

For example, an application creates a DataReader that uses Deadline QoS. In order to monitor for Deadline violations, the application gets the reader's StatusCondition and adds it to a WaitSet. If that Condition becomes active, the application invokes get_requested_deadline_missed_status to determine which instance experienced the deadline violation (using last_instance_handle). However, in the case that multiple instances have deadline violations since the last time status was checked (total_count_change > 1), the identity of all but the last of those instances is not available to the application.

This same concept applies to any of the uses of "last_*" in the Plain Communication Status structures.