RTI Connext Java API
Version 6.0.0
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Expresses the maximum duration (deadline) within which an instance is expected to be updated. More...
Public Attributes | |
final Duration_t | period |
Duration of the deadline period. | |
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final QosPolicyId_t | id |
The ID of this QoS policy. | |
final String | policy_name |
The name of this QoS policy. | |
Additional Inherited Members | |
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abstract boolean | equals (Object obj) |
abstract int | hashCode () |
String | toString () |
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Struct () | |
abstract void | pull_from_nativeI (long native_status) |
abstract void | push_to_nativeI (long native_status) |
Expresses the maximum duration (deadline) within which an instance is expected to be updated.
A com.rti.dds.subscription.DataReader 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.
A com.rti.dds.publication.DataWriter indicates that the application commits to write a new value (using the com.rti.dds.publication.DataWriter) for each instance managed by the com.rti.dds.publication.DataWriter at least once every period
.
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.
This policy is useful for cases where a com.rti.dds.topic.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 'matches' a com.rti.dds.publication.DataWriter and a com.rti.dds.subscription.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 com.rti.dds.infrastructure.Listener or com.rti.dds.infrastructure.Condition 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 com.rti.dds.infrastructure.Listener or com.rti.dds.infrastructure.Condition.
The value offered is considered compatible with the value requested if and only if the inequality offered period <= requested period holds.
The setting of the 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.
An attempt to set these policies in an inconsistent manner will result in com.rti.dds.infrastructure.RETCODE_INCONSISTENT_POLICY in set_qos (abstract), or the com.rti.dds.infrastructure.Entity will not be created.
For a com.rti.dds.subscription.DataReader, the DEADLINE policy and com.rti.dds.infrastructure.TimeBasedFilterQosPolicy may interact such that even though the com.rti.dds.publication.DataWriter is writing samples fast enough to fulfill its commitment to its own deadline, the com.rti.dds.subscription.DataReader may see violations of its deadline. This happens because RTI Connext will drop any samples received within the com.rti.dds.infrastructure.TimeBasedFilterQosPolicy.minimum_separation. To avoid triggering the com.rti.dds.subscription.DataReader's deadline, even though the matched com.rti.dds.publication.DataWriter is meeting its own deadline, set the two QoS parameters so that:
reader deadline >= reader minimum_separation + writer deadline
See com.rti.dds.infrastructure.TimeBasedFilterQosPolicy for more information about the interactions between deadlines and time-based filters.
final Duration_t period |
Duration of the deadline period.
[default] com.rti.dds.infrastructure.Duration_t.DURATION_INFINITE
[range] [1 nanosec, 1 year] or com.rti.dds.infrastructure.Duration_t.DURATION_INFINITE, >= com.rti.dds.infrastructure.TimeBasedFilterQosPolicy.minimum_separation