topic_state_monitor

Purpose

This node monitors input topic for abnormalities such as timeout and low frequency. The result of topic status is published as diagnostics.

Inner-workings / Algorithms

The types of topic status and corresponding diagnostic status are following.

Topic status	Diagnostic status	Description
OK	OK	The topic has no abnormalities
NotReceived	ERROR	The topic has not been received yet
WarnRate	WARN	The frequency of the topic is dropped
ErrorRate	ERROR	The frequency of the topic is significantly dropped
Timeout	ERROR	The topic subscription is stopped for a certain time

Inputs / Outputs

Input

Name	Type	Description
any name	any type	Subscribe target topic to monitor

Output

Name	Type	Description
/diagnostics	diagnostic_msgs/DiagnosticArray	Diagnostics outputs

Parameters

Node Parameters

Name	Type	Default Value	Description
topic	string	-	Name of target topic
topic_type	string	-	Type of target topic (used if the topic is not transform)
frame_id	string	-	Frame ID of transform parent (used if the topic is transform)
child_frame_id	string	-	Frame ID of transform child (used if the topic is transform)
transient_local	bool	false	QoS policy of topic subscription (Transient Local/Volatile)
best_effort	bool	false	QoS policy of topic subscription (Best Effort/Reliable)
diag_name	string	-	Name used for the diagnostics to publish
update_rate	double	10.0	Timer callback period [Hz]

Core Parameters

Name	Type	Default Value	Description
warn_rate	double	0.5	If the topic rate is lower than this value, the topic status becomes WarnRate
error_rate	double	0.1	If the topic rate is lower than this value, the topic status becomes ErrorRate
timeout	double	1.0	If the topic subscription is stopped for more than this time [s], the topic status becomes Timeout
window_size	int	10	Window size of target topic for calculating frequency

Assumptions / Known limits

TBD.