DDS_DeadlineQosPolicy Struct Reference

<<cert>> Expresses the maximum duration (deadline) within which an instance is expected to be updated. More...

Data Fields
struct DDS_Duration_t	period
	Duration of the deadline period.

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Detailed Description

<<cert>> Expresses the maximum duration (deadline) within which an instance is expected to be updated.

DDS_DataReader expects a new sample updating the value of each instance at least once every period. DDS_DataWriter indicates that the application commits to write a new value (using the DDS_DataWriter) for each instance managed by the DDS_DataWriter at least once every period.

If a DDS_DataReader stops receiving samples, it will take at most (period + (period / 8)) to detect that the deadline has been missed. The deadline period starts again when the next sample is received.

Entity:

DDS_Topic, DDS_DataReader, DDS_DataWriter

Status:

DDS_OFFERED_DEADLINE_MISSED_STATUS, DDS_REQUESTED_DEADLINE_MISSED_STATUS, DDS_OFFERED_INCOMPATIBLE_QOS_STATUS, DDS_REQUESTED_INCOMPATIBLE_QOS_STATUS

Properties:

RxO = YES
Changeable = NO

Usage

This policy is useful for cases where a DDS_Topic is expected to have each instance updated periodically. On the publishing side this setting establishes a contract that the application must meet. On the subscribing side the setting establishes a minimum requirement for the remote publishers that are expected to supply the data values.

When RTI Connext Micro 'matches' a DDS_DataWriter and a DDS_DataReader it checks whether the settings are compatible (i.e., offered deadline <= requested deadline); if they are not, the two entities are informed (via the DDS_Listener 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 Micro and the application is informed of any violations by means of the proper DDS_Listener.

Compatibility

The value offered is considered compatible with the value requested if and only if the inequality offered period <= requested period evaluates to 'TRUE'.

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Field Documentation

struct DDS_Duration_t DDS_DeadlineQosPolicy::period

Duration of the deadline period.

[default] DDS_DURATION_INFINITE

[range] [1 nanosec, 1 year] or DDS_DURATION_INFINITE