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.

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

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

Name	Type	Description
`/diagnostics`	`diagnostic_msgs/DiagnosticArray`	Diagnostics outputs

Name	Type	Default Value	Description
`update_rate`	double	10.0	Timer callback period [Hz]
`window_size`	int	10	Window size of target topic for calculating frequency

Name	Type	Default Value	Description
`topic`	string	-	Name of target topic
`topic_type`	string	-	Type of target topic
`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
`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`

TBD.