Bags API

Starting from version 2.7.0, bag files are recorded continuously. When the total storage size exceeds a predefined limit, the oldest files are automatically purged.

Get Bag List

curl http://192.168.25.25:8090/bags/

[
  {
    "filename": "2023-10-31_14-30-00.bag",
    "size": "6.8KB",
    "size_bytes": 6922,
    "end": "31-Oct-2023 14:36:17",
    "download_url": "http://192.168.25.25:8090/bags/2023-10-31_14-30-00.bag/download"
  },
  {
    "filename": "2023-11-01_13-50-00.bag",
    "size": "4.1KB",
    "size_bytes": 4172,
    "end": "01-Nov-2023 13:55:10",
    "download_url": "http://192.168.25.25:8090/bags/2023-11-01_13-50-00.bag/download"
  }
]

Bag Player API

The Bag Player API allows for replaying ROS bag files online. It provides metadata about the bag and enables downloading message chunks within specific time ranges.

1. Get Bag Metadata

Fetches general information about the bag file, such as the total number of messages and the time duration.

Success Response

Code: 200 OK
Content:
```
{
  "total_messages": 5000,
  "start_time": 1674650000,
  "end_time": 1674653600
}
```
- total_messages: Integer representing the total number of messages in the bag.
- start_time: Integer timestamp (Unix epoch) of the first message.
- end_time: Integer timestamp (Unix epoch) of the last message.

2. Get Message Chunks

Fetches messages within a specific time range. This is used by the frontend to stream or download chunks of the bag.

Request

GET /bags/<filename>/player?start_time=<float>&end_time=<float>

Query Parameters

Parameter	Type	Required	Description
`start_time`	float	Yes	The start of the time range in seconds (Unix epoch).
`end_time`	float	Yes	The end of the time range in seconds (Unix epoch).

Success Response

Code: 200 OK
Content:
```
{
  "total_messages": 5000,
  "start_time": 1674650000,
  "end_time": 1674653600,
  "messages": [
    {
      "topic": "/some_topic",
      "field1": "value1",
      "__stamp": 1674650010.123,
      "__latched": true
    },
    ...
  ]
}
```
- messages: A list of JSON-converted ROS messages.
- Each message includes:
  - __stamp: High-precision timestamp when the message was recorded.
  - __latched: Boolean flag set to true if the message belongs to a latched topic. This includes both backfilled messages (previous state) and messages occurring within the requested time range.

Special Behavior: Latched Topics

When a time range is requested, the API automatically includes the most recent message for "latched" topics that occurred before the start_time. This ensures the player has the current state for static or slowly-changing topics (like maps or configurations) as soon as the chunk starts.

Latched topics include:

/map/info
/alerts
/map_image
/sensor_manager_state
/robot_model
/nearby_robot_footprints
/path
/local_path
/detected_features/racks_v2
/detected_features/pallets
/detected_features/chargers
/planning_state
/jack_state
/towing_state

Caching

Responses are cached with the following header: Cache-Control: public, max-age=2592000 (30 days)

Error Responses

Code: 400 BAD REQUEST
Content: {"error": "string explaining the error"} (e.g., if the bag file is not found or corrupted).