DDS::ReaderDataLifecycleQosPolicy Struct Reference

Controls how a DataReader manages the lifecycle of the data that it has received. More...

#include <managed_infrastructure.h>

Static Public Member Functions
static System::String^	get_readerdatalifecycle_qos_policy_name ()
	Stringified human-readable name for DDS::ReaderDataLifecycleQosPolicy.

Public Attributes
Duration_t	autopurge_nowriter_samples_delay
	Minimum duration for which the DDS::DataReader will maintain information regarding an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.
Duration_t	autopurge_disposed_samples_delay
	Minimum duration for which the DDS::DataReader will maintain samples for an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE.
Duration_t	autopurge_disposed_instances_delay
	<<extension>> Minimum duration for which the DDS::DataReader will maintain an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE.

Detailed Description

Controls how a DataReader manages the lifecycle of the data that it has received.

When a DataReader receives data, it is stored in a receive queue for the DataReader. The user application may either take the data from the queue or leave it there.

This QoS policy controls whether or not RTI Connext will automatically remove data from the receive queue (so that user applications cannot access it afterwards) when it detects that there are no more DataWriters alive for that data. It specifies how long a DDS::DataReader must retain information regarding instances that have the instance_state DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.

Note: This policy is not concerned with keeping reliable reader state or discovery information.

The DDS::DataReader internally maintains the samples that have not been "taken" by the application, subject to the constraints imposed by other QoS policies such as DDS::HistoryQosPolicy and DDS::ResourceLimitsQosPolicy.

The DDS::DataReader also maintains information regarding the identity, view_state and instance_state of data instances even after all samples have been taken. This is needed to properly compute the states when future samples arrive.

Under normal circumstances the DDS::DataReader can only reclaim all resources for instances for which there are no writers and for which all samples have been 'taken'. The last sample the DDS::DataReader will have taken for that instance will have an instance_state of either DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE or DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE depending on whether or not the last writer that had ownership of the instance disposed it.

In the absence of READER_DATA_LIFECYCLE, this behavior could cause problems if the application forgets to take those samples. "Untaken" samples will prevent the DDS::DataReader from reclaiming the resources and they would remain in the DDS::DataReader indefinitely.

A DataReader can also reclaim all resources for instances that have an instance state of DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE and for which all DDS samples have been 'taken'. DataReaders will only reclaim resources in this situation when the autopurge_disposed_instances_delay has been set to zero.

For keyed Topics, the consideration of removing data samples from the receive queue is done on a per instance (key) basis. Thus when RTI Connext detects that there are no longer DataWriters alive for a certain key value of a Topic (an instance of the Topic), it can be configured to remove all data samples for that instance (key).

Entity:

DDS::DataReader

Properties:

RxO = N/A
Changeable = YES

Member Data Documentation

Duration_t DDS::ReaderDataLifecycleQosPolicy::autopurge_nowriter_samples_delay

Minimum duration for which the DDS::DataReader will maintain information regarding an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_NO_WRITERS_INSTANCE_STATE.

At some point after this time elapses, the DDS::DataReader will purge all internal information regarding the instance, any "untaken" samples will also be lost.

[default] DDS::Duration_t::DURATION_INFINITE

[range] [1 nanosec, 1 year] or DDS::Duration_t::DURATION_INFINITE

Duration_t DDS::ReaderDataLifecycleQosPolicy::autopurge_disposed_samples_delay

Minimum duration for which the DDS::DataReader will maintain samples for an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE.

At some point after this time elapses, the DDS::DataReader will purge all samples for the instance.

[default] DDS::Duration_t::DURATION_INFINITE

[range] [1 nanosec, 1 year] or DDS::Duration_t::DURATION_INFINITE

Duration_t DDS::ReaderDataLifecycleQosPolicy::autopurge_disposed_instances_delay

<<extension>> Minimum duration for which the DDS::DataReader will maintain an instance once its instance_state becomes DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE.

At some point after this time elapses, the DDS::DataReader will purge all knowledge of the instance.

The only currently supported values are 0 and DDS::Duration_t::DURATION_INFINITE. A value of 0 will purge an instance's state immediately after the instance state transitions to DDS::InstanceStateKind::NOT_ALIVE_DISPOSED_INSTANCE_STATE, as long as all samples, including the dispose sample, associated with that instance have been 'taken'.

[default] DDS::Duration_t::DURATION_INFINITE