Statuses

Entities in DDS have statuses that indicate the internal state and/or history of an entity. These statuses signal Waitsets and Listeners, and are different between types of DDS entities. The following table lists the fields for each status and their meaning:

CycloneDDS-CXX Status entities and fields

CDDS-CXX Entity Type

Status Entity

Associated Fields

Meaning of field

DomainParticipant

Publisher

Subscriber

Topic

InconsistentTopicStatus

total_count

the total number of times an inconsistent topic was encountered

total_count_change

the change in total_count since last being retrieved

DataWriter

OfferedDeadlineMissedStatus

total_count

the total number of times an offered deadline was missed by the writer committing itself to the deadline

total_count_change

the change in total_count since last being retrieved

last_instance_handle

handle to the last instance in a writer missing a committed deadline

OfferedIncompatibleQosStatus

total_count

the total number of times the writer encountered a reader requesting a QoS which was was not compatible with the one offered by the writer

total_count_change

the change in total_count since last being retrieved

last_policy_id

the last id of the QoSPolicy which was incompatible

policies

a collection of QoSPolicy ids and the number times they were found to be incompatible

LivelinessLostStatus

total_count

the total number of times a writer became “dead” by not asserting its liveliness often enough

total_count_change

the change in total_count since last being retrieved

PublicationMatchedStatus

total_count

the total number of times a writer has encountered a reader it has a “match” with

total_count_change

the change in total_count since last being retrieved

current_count

the current number of readers a writer has a “match” with

current_count_change

the change in current_count since last being retrieved

last_subscription_handle

handle to the last reader causing this status to change

DataReader

RequestedDeadlineMissedStatus

total_count

total number of missed deadlines for instances read by the reader

total_count_change

the change in total_count since last being retrieved

last_instance_handle

the last instance handle to miss a deadline

RequestedIncompatibleQosStatus

total_count

the total number of times the reader encountered a writer offering a QoS which was was not compatible with the one requested by the reader

total_count_change

the change in total_count since last being retrieved

last_policy_id

the last id of the QoSPolicy which was incompatible

policies

a collection of QoSPolicy ids and the number times they were found to be incompatible

SampleRejectedStatus

total_count

total number of samples rejected by the reader

total_count_change

the change in total_count since last being retrieved

last_reason

the last reason for rejecting a sample

last_instance_handle

handle to last instance encountering a rejected sample

LivelinessChangedStatus

alive_count

the total number of matching writers that are alive

alive_count_change

the change in alive_count since last being retrieved

not_alive_count

the total number of matching writers that are dead

not_alive_count_change

the change in not_alive_count since last being retrieved

last_publication_handle

handle to the last writer causing this to change

SubscriptionMatchedStatus

total_count

the total number of times a reader has encountered a writer it has a “match” with

total_count_change

the change in total_count since last being retrieved

current_count

the current number of writers a reader has a “match” with

current_count_change

the change in current_count since last being retrieved

last_publication_handle

handle to the writer causing this status to change

SampleLostStatus

total_count

the total number of samples lost in the topic

total_count_change

the change in total_count since last being retrieved

Fields of status objects containing counts of events will have both a cumulative and interval count, where the cumulative count will keep track of all changes during the lifetime of the DDS entity, and the interval count is the number of changes since the previous readout of the status. To access the statuses, use the following functions on the entity:

CycloneDDS-CXX Status accessors

CDDS-CXX Entity Type

Status Entity

Accessor

Topic

InconsistentTopicStatus

inconsistent_topic_status

DataWriter

OfferedDeadlineMissedStatus

offered_deadline_missed_status

OfferedIncompatibleQosStatus

offered_incompatible_qos_status

LivelinessLostStatus

liveliness_lost_status

PublicationMatchedStatus

publication_matched_status

DataReader

RequestedDeadlineMissedStatus

requested_deadline_missed_status

RequestedIncompatibleQosStatus

requested_incompatible_status

SampleRejectedStatus

sample_rejected_status

LivelinessChangedStatus

liveliness_changed_status

SubscriptionMatchedStatus

subscription_matched_status

SampleLostStatus

sample_lost_status

The following code fragment shows statuses that make a writer wait until readers are present:

dds::pub::DataWriter<DataType> wr(publisher, topic);
while (0 == wr.publication_matched_status().current_count())
        std::this_thread::sleep_for(std::chrono::milliseconds(20));

The writer polls the total number of readers that are receiving data from it at 20 millisecond intervals for as long as there are no readers.