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https://github.com/ros/rosbag_snapshot


https://github.com/ros/rosbag_snapshot

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# rosbag_snapshot



Solution for [this ros_comm issue](https://github.com/ros/ros_comm/issues/1399) which acts similarly to the deprecated `rosrecord -s` command but with additional features. It is added as a new package here rather than patching `rosbag` based on [the discussion here](https://github.com/ros/ros_comm/pull/1414).



It subscribes to topics and maintains a buffer of recent messages like a dash cam. This is useful in live testing where unexpected events can occur which would be useful to have data on but the opportunity is missed if `rosbag record` was not running (disk space limits make always running `rosbag record` impracticable). Instead, users may run snapshot in the background and save data from the recent past to disk as needed.



## Usage



`rosbag_snapshot` can be configured through command line flags and with ROS params for more granular control. By default, the command will run in server mode (buffering data). When certain flags are used, program will act as a client by requesting that the server write data to disk or freezing the buffer to preserve interesting data until a user can decide what to write.



### CLI usage



```

$ rosrun rosbag_snapshot snapshot -h

Usage: snapshot [options] [topic1 topic2 ...]



Buffer recent messages until triggered to write or trigger an already running instance.



Options:

  -h [ --help ]                produce help message

  -t [ --trigger-write ]       Write buffer of selected topics to a bag file

  -p [ --pause ]               Stop buffering new messages until resumed or

                               write is triggered

  -r [ --resume ]              Resume buffering new messages, writing over

                               older messages as needed

  -n [ --no-clear ]            Flag to explicitly NOT clear buffer after writing

                               to a bag file (no tag will clear buffer)

  -s [ --size ] arg (=-1)      Maximum memory per topic to use in buffering in

                               MB. Default: no limit

  -d [ --duration ] arg (=30)  Maximum difference between newest and oldest

                               buffered message per topic in seconds. Default:

                               30

  -o [ --output-prefix ] arg   When in trigger write mode, prepend PREFIX to

                               name of writing bag file

  -O [ --output-filename ] arg When in trigger write mode, exact name of

                               written bag file

  --topic arg                  Topic to buffer. If triggering write, write only

                               these topics instead of all buffered topics.

  -c [ --compression ] arg     Compression type. Options are: LZ4, BZ2.

                               Default: uncompressed.

```



###### Hold a buffer of the last 30 seconds of data from selected topics until triggered to write

`rosrun rosbag_snapshot snapshot -d 30 /tf /odom /camera/image_color /camera/camera_info /velodyne_points`



###### Buffer the most recent gigabyte of the following topics in the camera namespace

`ROS_NAMESPACE=camera rosrun rosbag_snapshot snapshot -s 1000 image_rect_color camera_info`



### Example launch file

```



  

    

        default_duration_limit: 1  # Maximum time difference between newest and oldest message, seconds, overrides -d flag

        default_memory_limit: 0.1  # Maximum memory used by messages in each topic's buffer, MB, override -s flag

        clear_buffer: false        # No option / true will clear the buffer after writing to bag. False will not clear buffer

        compression: LZ4           # LZ4, BZ2, uncompressed

        topics:

            - test1                # Inherit defaults

            - test2:               # Override duration limit, inherit memory limit

                duration: 2

            - test3:               # Override both limits

                duration: -1       # Negative means no duration limit

                memory: 0.00

    

  



```



## Client examples



###### Write all buffered data to `.bag`

`rosrun rosbag_snapshot snapshot -t`



###### Write buffered data from selected topics to `new_lighting.bag`

`rosrun rosbag_snapshot snapshot -t -o new_lighting /camera/image_raw /camera/camera_info`



###### Write all buffered data to `/home/user/crashed_into_wall.bag`

`rosrun rosbag_snapshot snapshot -t -O /home/user/crashed_into_wall`



###### Pause buffering of new data, holding current buffer in memory until -t or -r is used

`rosrun rosbag_snapshot snapshot -p`



###### Resume buffering new data

`rosrun rosbag_snapshot snapshot -r`



###### Call trigger service manually, specifying absolute window start and stop time for written data



```

$ rosservice call /trigger_snapshot "filename: 'short_control_instability.bag'

topics:

- '/tf'

- '/odom'

- '/wrench'

- '/motors/cmd'

start_time:

  secs: 62516

  nsecs: 0

stop_time:

  secs: 62528

  nsecs: 0"

```



###### View status of buffered data (useful for future tools/GUI)



```

$ rostopic echo /snapshot_status

topics:

  -

    topic: "/test"

    node_pub: ''

    node_sub: "/snapshot_1527185221120605085"

    window_start:

      secs: 62516

      nsecs: 761000000

    window_stop:

      secs: 62521

      nsecs: 984000000

    delivered_msgs: 524

    dropped_msgs: 0

    traffic: 2096

    period_mean:

      secs: 0

      nsecs:         0

    period_stddev:

      secs: 0

      nsecs:         0

    period_max:

      secs: 0

      nsecs:         0

    stamp_age_mean:

      secs: 0

      nsecs:         0

    stamp_age_stddev:

      secs: 0

      nsecs:         0

    stamp_age_max:

      secs: 0

      nsecs:         0

enabled: True

---

```