Part 4 (Playing a Log)

In this section we’ll use the Ark tools to download a publically available log.

Type this:

./build/ark-download-log 85bdf7dc-d708-486e-9fcb-5afc8d2d1272 -o ~/tutorial_logs/

This will download the log 85bdf7dc-d708-486e-9fcb-5afc8d2d1272 into the tutorial logs directory in your home directory. It should complete without incident. Note that you will need catalog permissions to download the log, please request them from TBD.

Once completed, you should be able to run your pipeline:

./build/tutorial_pipeline ~/tutorial_logs/manifests/85bdf7dc-d708-486e-9fcb-5afc8d2d1272

If you see an error that looks like:

ImportError: Failed to load PyTorch C extensions

Then you need to adjust your PATH to use the Ark version of python. You can source the env.sh file to get an appropriate Python in your path.

At this point, you should see something like this:

(2022-06-21 14:38:56.266) [info] (version.cc:16) Starting execution with ARK_V2022.05.0-207-g0b8d9f2e/x86_64 (0b8d9f2e3d87a187e324fb6f904fcd63399600e3)
Connecting to host pipeline at '127.0.0.1:44057'
Connected to host pipeline.
(2022-06-21 14:38:58.835) [warn] (context.cc:689) The subscriber /realsense/color/image (in stage ImageDetectorStage) was not connected to any publisher.
(2022-06-21 14:38:58.835) [info] (http_server_stage.cc:884) HTTP Server is listening on "0.0.0.0:8080".
(2022-06-21 14:38:58.845) [info] (python_stage.cc:334) Sending KILL signal to the python process 'ImageDetectorStage'.
(2022-06-21 14:38:58.978) [info] (python_stage.cc:819) The python process 'ImageDetectorStage' is finishing clean up.
(2022-06-21 14:38:59.036) [error] (main_offboard.cc:371) Unhandled error during pipeline execution: Exception while starting LogReaderStage: The log reader was configured to play back zero messages. This typically means that there are no subscribers in your pipeline for any of the data contained within this log, so playing the log back is meaningless. Set force_playback_all_messages to true to avoid this (at a large performance cost).
FATAL: Exception while starting LogReaderStage: The log reader was configured to play back zero messages. This typically means that there are no subscribers in your pipeline for any of the data contained within this log, so playing the log back is meaningless. Set force_playback_all_messages to true to avoid this (at a large performance cost).

It will initialize Pytorch but not do too much else. Let’s move on to Step 5.