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 | rmw_take
- 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