LivelinessChangedStatus Class Reference

com.rti.dds.infrastructure.StatusKind.StatusKind.LIVELINESS_CHANGED_STATUS More...

Inherits Status.

Public Member Functions
	LivelinessChangedStatus ()
	The no-argument constructor for this status object.
	LivelinessChangedStatus (LivelinessChangedStatus src)
	A copy constructor.

Public Attributes
int	alive_count
	The total count of currently alive com.rti.dds.publication.DataWriter entities that write the com.rti.dds.topic.Topic that this com.rti.dds.subscription.DataReader reads.
int	not_alive_count
	The total count of currently not_alive com.rti.dds.publication.DataWriter entities that write the com.rti.dds.topic.Topic that this com.rti.dds.subscription.DataReader reads.
int	alive_count_change
	The change in the alive_count since the last time the listener was called or the status was read.
int	not_alive_count_change
	The change in the not_alive_count since the last time the listener was called or the status was read.
final InstanceHandle_t	last_publication_handle
	This InstanceHandle can be used to look up which remote com.rti.dds.publication.DataWriter was the last to cause this DataReader's status to change, using com.rti.dds.subscription.DataReader.get_matched_publication_data.

Additional Inherited Members
Protected Member Functions inherited from Struct
	Struct ()
abstract void	pull_from_nativeI (long native_status)
abstract void	push_to_nativeI (long native_status)

Detailed Description

com.rti.dds.infrastructure.StatusKind.StatusKind.LIVELINESS_CHANGED_STATUS

The com.rti.dds.subscription.DataReaderListener.on_liveliness_changed callback may be invoked for the following reasons:

• The liveliness of any com.rti.dds.publication.DataWriter matching this DataReader (as defined by the com.rti.dds.infrastructure.LivelinessQosPolicyKind setting) is lost.

• A DataWriter's liveliness is recovered after being lost.

• A new matching DataWriter has been discovered.

• A matching DataWriter has been deleted.

• A QoS Policy has changed such that a DataWriter that matched this DataReader before no longer matches (such as a change to the com.rti.dds.infrastructure.PartitionQosPolicy). In this case, RTI Connext will no longer keep track of the DataWriter's liveliness. Furthermore, consider two scenarios:

  • DataWriter was alive when it and DataReader stopped matching: com.rti.dds.subscription.LivelinessChangedStatus.alive_count will decrease (since there's one less matching alive DataWriter) and com.rti.dds.subscription.LivelinessChangedStatus.not_alive_count will remain the same (since the DataWriter is still alive).

  • DataWriter was not alive when it and DataReader stopped matching: com.rti.dds.subscription.LivelinessChangedStatus.alive_count will remain the same (since the matching DataWriter was not alive) and com.rti.dds.subscription.LivelinessChangedStatus.not_alive_count will decrease (since there's one less not-alive matching DataWriter).

    Note: There are several ways that a DataWriter and DataReader can become incompatible after the DataWriter has lost liveliness. For example, when the com.rti.dds.infrastructure.LivelinessQosPolicyKind is set to DDS_MANUAL_BY_PARTICIPANT_LIVELINESS_QOS, it is possible that the DataWriter has not asserted its liveliness in a timely manner, and then a QoS change occurs on the DataWriter or DataReader that makes the entities incompatible.

• A QoS Policy (such as the com.rti.dds.infrastructure.PartitionQosPolicy) has changed such that a DataWriter that was unmatched with the DataReader now matches.

Constructor & Destructor Documentation

LivelinessChangedStatus

(

)

The no-argument constructor for this status object.

LivelinessChangedStatus

(

LivelinessChangedStatus

src

)

A copy constructor.

Exceptions

NullPointerException

if the given status is null.

Member Data Documentation

int alive_count

The total count of currently alive com.rti.dds.publication.DataWriter entities that write the com.rti.dds.topic.Topic that this com.rti.dds.subscription.DataReader reads.

int not_alive_count

The total count of currently not_alive com.rti.dds.publication.DataWriter entities that write the com.rti.dds.topic.Topic that this com.rti.dds.subscription.DataReader reads.

int alive_count_change

The change in the alive_count since the last time the listener was called or the status was read.

int not_alive_count_change

The change in the not_alive_count since the last time the listener was called or the status was read.

Note that a positive not_alive_count_change means one of the following:

• The DomainParticipant containing the matched DataWriter has lost liveliness or has been deleted.

• The matched DataWriter has lost liveliness or has been deleted.

final InstanceHandle_t last_publication_handle

This InstanceHandle can be used to look up which remote com.rti.dds.publication.DataWriter was the last to cause this DataReader's status to change, using com.rti.dds.subscription.DataReader.get_matched_publication_data.

It's possible that the DataWriter has been purged from the discovery database. (See the "What is Discovery?" section of the User's Manual.) If so, the com.rti.dds.subscription.DataReader.get_matched_publication_data method will not be able to return information about the DataWriter. In this case, the only way to get information about the lost DataWriter is if you cached the information previously.