Subscription

Topic message is received by subscription via inter-process communication or intra-process one. Then, Subscription object has common data fields, but different value is filled in source_timestamp field.

Inter process communication

A simplified sequence diagram focusing only on the relevant events is shown below.

to_dataframe API returns a table which has the following columns.

Column	Type	Description
callback_start_timestamp	System time	Callback start time
message_timestamp	Message data	Time of header.stamp. Zero when header is not defined.
source_timestamp	Depends on DDS	Timestamp to used for binding with subscription.

See also

• Subscription API
• Trace points | dispatch_subscription_callback
• Trace points | callback_start

Intra process communication

to_dataframe API returns a table which has the following columns.

Column	Type	Description
callback_start_timestamp	System time	Callback start time
message_timestamp	Message data	Time of header.stamp. Zero when header is not defined.
source_timestamp	Depends on DDS (Optional)	NaN.

See also

• Subscription API
• Trace points | dispatch_intra_process_subscription_callback
• Trace points | callback_start