10.1.1. Statistics Topic names

Data collected by the Fast DDS Statistics module is published in one of the topics listed below. In order to simplify its use, the API provides aliases for the different statistics topics (see Topic names). The following table shows the correlation between the topic name and the corresponding alias.

Topic name

Alias

_fastdds_statistics_history2history_latency

HISTORY_LATENCY_TOPIC

_fastdds_statistics_network_latency

NETWORK_LATENCY_TOPIC

_fastdds_statistics_publication_throughput

PUBLICATION_THROUGHPUT_TOPIC

_fastdds_statistics_subscription_throughput

SUBSCRIPTION_THROUGHPUT_TOPIC

_fastdds_statistics_rtps_sent

RTPS_SENT_TOPIC

_fastdds_statistics_rtps_lost

RTPS_LOST_TOPIC

_fastdds_statistics_heartbeat_count

HEARTBEAT_COUNT_TOPIC

_fastdds_statistics_acknack_count

ACKNACK_COUNT_TOPIC

_fastdds_statistics_nackfrag_count

NACKFRAG_COUNT_TOPIC

_fastdds_statistics_gap_count

GAP_COUNT_TOPIC

_fastdds_statistics_data_count

DATA_COUNT_TOPIC

_fastdds_statistics_resent_datas

RESENT_DATAS_TOPIC

_fastdds_statistics_sample_datas

SAMPLE_DATAS_TOPIC

_fastdds_statistics_pdp_packets

PDP_PACKETS_TOPIC

_fastdds_statistics_edp_packets

EDP_PACKETS_TOPIC

_fastdds_statistics_discovered_entity

DISCOVERY_TOPIC

_fastdds_statistics_physical_data

PHYSICAL_DATA_TOPIC

10.1.1.1. HISTORY_LATENCY_TOPIC

The _fastdds_statistics_history2history_latency statistics topic collects data related with the latency between any two matched endpoints. This measurement provides information about the DDS overall latency independent of the user’s application overhead. Specifically, the measured latency corresponds to the time spent between the instant when the sample is written to the DataWriter’s history and the time when the sample is added to the DataReader’s history and the notification is issued to the corresponding user’s callback.

10.1.1.2. NETWORK_LATENCY_TOPIC

The _fastdds_statistics_network_latency statistics topic collects data related with the network latency between any two communicating locators. This measurement provides information about the transport layer latency. The measured latency corresponds to the time spent between the message being written in the RTPSMessageGroup until the message being received in the MessageReceiver.

10.1.1.3. PUBLICATION_THROUGHPUT_TOPIC

The _fastdds_statistics_publication_throughput statistics topic collects the amount of data that is being sent by each DataWriter. This measurement provides information about the publication’s throughput.

10.1.1.4. SUBSCRIPTION_THROUGHPUT_TOPIC

The _fastdds_statistics_subscription_throughput statistics topic collects the amount of data that is being received by each DataReader. This measurement provides information about the subscription’s throughput.

10.1.1.5. RTPS_SENT_TOPIC

The _fastdds_statistics_rtps_sent statistics topic collects the number of RTPS packets and bytes that are being sent from each DDS entity to each locator.

10.1.1.6. RTPS_LOST_TOPIC

The _fastdds_statistics_rtps_lost statistics topic collects the number of RTPS packets and bytes that are being lost in the transport layer (dropped somewhere in between) in the communication between each DDS entity and locator.

10.1.1.7. HEARTBEAT_COUNT_TOPIC

The _fastdds_statistics_heartbeat_count statistics topic collects the number of heartbeat messages sent by each user’s DataWriter. This topic does not apply to builtin (related to Discovery) and statistics DataWriters. Heartbeat messages are only sent if the ReliabilityQosPolicy is set to RELIABLE_RELIABILITY_QOS. These messages report the DataWriter’s status.

10.1.1.8. ACKNACK_COUNT_TOPIC

The _fastdds_statistics_acknack_count statistics topic collects the number of acknack messages sent by each user’s DataReader. This topic does not apply to builtin DataReaders (related to Discovery). Acknack messages are only sent if the ReliabilityQosPolicy is set to RELIABLE_RELIABILITY_QOS. These messages report the DataReader’s status.

10.1.1.9. NACKFRAG_COUNT_TOPIC

The _fastdds_statistics_nackfrag_count statistics topic collects the number of nackfrag messages sent by each user’s DataReader. This topic does not apply to builtin DataReaders (related to Discovery). Nackfrag messages are only sent if the ReliabilityQosPolicy is set to RELIABLE_RELIABILITY_QOS. These messages report the data fragments that have not been received yet by the DataReader.

10.1.1.10. GAP_COUNT_TOPIC

The _fastdds_statistics_gap_count statistics topic collects the number of gap messages sent by each user’s DataWriter. This topic does not apply to builtin (related to Discovery) and statistics DataWriters. Gap messages are only sent if the ReliabilityQosPolicy is set to RELIABLE_RELIABILITY_QOS. These messages report that some specific samples are not relevant to a specific DataReader.

10.1.1.11. DATA_COUNT_TOPIC

The _fastdds_statistics_data_count statistics topic collects the total number of user’s data messages and data fragments (in case that the message size is large enough to require RTPS fragmentation) that have been sent by each user’s DataWriter. This topic does not apply to builtin (related to Discovery) and statistics DataWriters.

10.1.1.12. RESENT_DATAS_TOPIC

The _fastdds_statistics_resent_data statistics topic collects the total number of user’s data messages and data fragments (in case that the message size is large enough to require RTPS fragmentation) that have been necessary to resend by each user’s DataWriter. This topic does not apply to builtin (related to Discovery) and statistics DataWriters.

10.1.1.13. SAMPLE_DATAS_TOPIC

The _fastdds_statistics_sample_datas statistics topic collects the number of user’s data messages (or data fragments in case that the message size is large enough to require RTPS fragmentation) that have been sent by the user’s DataWriter to completely deliver a single sample. This topic does not apply to builtin (related to Discovery) and statistics DataWriters.

10.1.1.14. PDP_PACKETS_TOPIC

The _fastdds_statistics_pdp_packets statistics topic collects the number of PDP discovery traffic RTPS packets transmitted by each DDS DomainParticipant. PDP packets are the data messages exchanged during the PDP discovery phase (see Discovery phases for more information).

10.1.1.15. EDP_PACKETS_TOPIC

The _fastdds_statistics_edp_packets statistics topic collects the number of EDP discovery traffic RTPS packets transmitted by each DDS DomainParticipant. EDP packets are the data messages exchanged during the EDP discovery phase (see Discovery phases for more information).

10.1.1.16. DISCOVERY_TOPIC

The _fastdds_statistics_discovered_entity statistics topic reports the time when each local DomainParticipant discovers any remote DDS entity (with the exception of those DDS entities related with the Fast DDS Statistics module).

10.1.1.17. PHYSICAL_DATA_TOPIC

The _fastdds_statistics_physical_data statistics topic reports the host, user and process where the Fast DDS Statistics module is running.