|Duration of the deadline period. |
A DDSDataReader expects a new sample updating the value of each instance at least once every
period. That is,
period specifies the maximum expected elapsed time between arriving data samples.
This QoS can be used during system integration to ensure that applications have been coded to meet design specifications.
It can also be used during run time to detect when systems are performing outside of design specifications. Receiving applications can take appropriate actions to prevent total system failure when data is not received in time. For topics on which data is not expected to be periodic,
period should be set to an infinite value.
When RTI Connext 'matches' a DDSDataWriter and a DDSDataReader it checks whether the settings are compatible (i.e., offered deadline <= requested deadline); if they are not, the two entities are informed (via the DDSListener or DDSCondition mechanism) of the incompatibility of the QoS settings and communication will not occur.
Assuming that the reader and writer ends have compatible settings, the fulfilment of this contract is monitored by RTI Connext and the application is informed of any violations by means of the proper DDSListener or DDSCondition.DEADLINE policy must be set consistently with that of the TIME_BASED_FILTER.
For these two policies to be consistent the settings must be such that deadline period >= minimum_separation.
For a DDSDataReader, the DEADLINE policy and DDS_TimeBasedFilterQosPolicy may interact such that even though the DDSDataWriter is writing samples fast enough to fulfill its commitment to its own deadline, the DDSDataReader may see violations of its deadline. This happens because RTI Connext will drop any samples received within the DDS_TimeBasedFilterQosPolicy::minimum_separation. To avoid triggering the DDSDataReader's deadline, even though the matched DDSDataWriter is meeting its own deadline, set the two QoS parameters so that:
reader deadline >= reader minimum_separation + writer deadline
See DDS_TimeBasedFilterQosPolicy for more information about the interactions between deadlines and time-based filters.