Python segfault with action graph in scene

[pweids]

I’m trying to load my own USD file using the “USD Load Sample” python script. I’ve noticed when I try to load and play a USD file with an action graph in it, Python throw a seg fault.

Fatal Python error: Segmentation fault

If I delete my action graph (which is blank, by the way), the USD runs fine.

I’m wondering if there’s some extension I need to enable to get the action graph to run properly?

I’m currently importing these two:

enable_extension("omni.graph.core")
enable_extension("omni.graph.action")

(The Action Graph will eventually publish a ROS2 clock, but I don’t think that’s the issue).

[pweids]

I’ve gotten a little more into the issue here. It seems to be a problem with the ROS2 bridge extension.

I opened Isaac sim and saved a completely blank USD file (saved as “blank.usd”). If I load that scene with the following script (based on the example), it will fail if the # enable_extension("omni.isaac.ros2_bridge") line is uncommented:

import sys

from isaacsim import SimulationApp

kit = SimulationApp({"headless": True})

from omni.isaac.core.utils.extensions import enable_extension
# enable_extension("omni.isaac.ros2_bridge")


import carb
import omni

usd_path = "/isaac-sim/workspaces/blank.usd"
omni.usd.get_context().open_stage(usd_path)

# Wait two frames so that stage starts loading
kit.update()
kit.update()

print("Loading stage...")
from omni.isaac.core.utils.stage import is_stage_loading

while is_stage_loading():
    kit.update()
print("Loading Complete")
omni.timeline.get_timeline_interface().play()
while kit.is_running():
    # Run in realtime mode, we don't specify the step size
    kit.update()

omni.timeline.get_timeline_interface().stop()
kit.close()

Here’s the output:

# code object from '/isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/__pycache__/TestOgnROS2ServiceServerRequest.cpython-310.pyc'
import 'omni.isaac.ros2_bridge.ogn.tests.TestOgnROS2ServiceServerRequest' # <_frozen_importlib_external.SourceFileLoader object at 0x7f71e79cff40>
# /isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/__pycache__/TestOgnROS2PublishImage.cpython-310.pyc matches /isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/TestOgnROS2PublishImage.py
# code object from '/isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/__pycache__/TestOgnROS2PublishImage.cpython-310.pyc'
import 'omni.isaac.ros2_bridge.ogn.tests.TestOgnROS2PublishImage' # <_frozen_importlib_external.SourceFileLoader object at 0x7f71e79cf700>
# /isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/__pycache__/TestOgnROS2SubscribeTransformTree.cpython-310.pyc matches /isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/TestOgnROS2SubscribeTransformTree.py
# code object from '/isaac-sim/exts/omni.isaac.ros2_bridge/omni/isaac/ros2_bridge/ogn/tests/__pycache__/TestOgnROS2SubscribeTransformTree.cpython-310.pyc'
import 'omni.isaac.ros2_bridge.ogn.tests.TestOgnROS2SubscribeTransformTree' # <_frozen_importlib_external.SourceFileLoader object at 0x7f71e79cdd50>
Fatal Python error: Segmentation fault

Thread 0x00007f62db7ff640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f710d9fe640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f70d7fff640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f711d5fe640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f711fdf8640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f72fe9bdb80 (most recent call first):
  File "/isaac-sim/exts/omni.isaac.kit/omni/isaac/kit/simulation_app.py", line 504 in update
  File "/isaac-sim/./workspaces/load_stage.py", line 27 in <module>
./python.sh: line 41: 20336 Segmentation fault      (core dumped) $python_exe "$@" $args
There was an error running python

I’ve verified that ROS2 is sourced when running by using this shell script:

#!/bin/bash

# Source ROS2 setup script
source /opt/ros/humble/setup.bash
source /isaac-sim/workspaces/ros_ws/install/setup.bash

# Check if ROS2 was sourced successfully
if [ "$ROS_DISTRO" != "humble" ]; then
  echo "Failed to source ROS2 Humble. Exiting."
  exit 1
fi

# Change directory to /isaac-sim
cd /isaac-sim

# Run the python script
./python.sh -v ./workspaces/load_stage.py

Do I need to import some other extension first? Or what could be the issue?

[pweids]

More context, it happens after the first kit.update() call. Here’s my REPL session:

>>> from isaacsim import SimulationApp
>>> kit = SimulationApp({"headless": True})
...
>>> from omni.isaac.core.utils.extensions import enable_extension
>>> enable_extension("omni.isaac.ros2_bridge")
...
>>> import omni
>>> usd_path = "/isaac-sim/workspaces/blank.usd"
>>> omni.usd.get_context().open_stage(usd_path)
True
>>> kit.update()
Fatal Python error: Segmentation fault

Thread 0x00007f21417fc640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f2f3effd640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f2f5dfff640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f2f5d7fe640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f2f5fff8640 (most recent call first):
  File "/isaac-sim/kit/python/lib/python3.10/concurrent/futures/thread.py", line 81 in _worker
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 953 in run
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 1016 in _bootstrap_inner
  File "/isaac-sim/kit/python/lib/python3.10/threading.py", line 973 in _bootstrap

Thread 0x00007f313f0f1b80 (most recent call first):
  File "/isaac-sim/exts/omni.isaac.kit/omni/isaac/kit/simulation_app.py", line 504 in update
  File "<stdin>", line 1 in <module>

Extension modules: psutil._psutil_linux, psutil._psutil_posix, omni.mdl.pymdlsdk._pymdlsdk, numpy.core._multiarray_umath, numpy.core._multiarray_tests, numpy.linalg._umath_linalg, numpy.fft._pocketfft_internal, numpy.random._common, numpy.random.bit_generator, numpy.random._bounded_integers, numpy.random._mt19937, numpy.random.mtrand, numpy.random._philox, numpy.random._pcg64, numpy.random._sfc64, numpy.random._generator, PIL._imaging, PIL._imagingft, scipy._lib._ccallback_c, scipy.ndimage._nd_image, scipy.special._ufuncs_cxx, scipy.special._ufuncs, scipy.special._specfun, scipy.special._comb, scipy.linalg._fblas, scipy.linalg._flapack, scipy.linalg._cythonized_array_utils, scipy.linalg._flinalg, scipy.linalg._solve_toeplitz, scipy.linalg._matfuncs_sqrtm_triu, scipy.linalg.cython_lapack, scipy.linalg.cython_blas, scipy.linalg._matfuncs_expm, scipy.linalg._decomp_update, scipy.sparse._sparsetools, _csparsetools, scipy.sparse._csparsetools, scipy.sparse.linalg._isolve._iterative, scipy.sparse.linalg._dsolve._superlu, scipy.sparse.linalg._eigen.arpack._arpack, scipy.sparse.csgraph._tools, scipy.sparse.csgraph._shortest_path, scipy.sparse.csgraph._traversal, scipy.sparse.csgraph._min_spanning_tree, scipy.sparse.csgraph._flow, scipy.sparse.csgraph._matching, scipy.sparse.csgraph._reordering, scipy.special._ellip_harm_2, _ni_label, scipy.ndimage._ni_label, torch._C, torch._C._fft, torch._C._linalg, torch._C._nested, torch._C._nn, torch._C._sparse, torch._C._special, scipy.spatial._ckdtree, scipy._lib.messagestream, scipy.spatial._qhull, scipy.spatial._voronoi, scipy.spatial._distance_wrap, scipy.spatial._hausdorff, scipy.spatial.transform._rotation, osqp._osqp, multidict._multidict, yarl._quoting_c, aiohttp._helpers, aiohttp._http_writer, aiohttp._http_parser, aiohttp._websocket, _cffi_backend, frozenlist._frozenlist, scipy.io.matlab._mio_utils, scipy.io.matlab._streams, scipy.io.matlab._mio5_utils, yaml._yaml, cv2 (total: 78)
./python.sh: line 41: 24398 Segmentation fault      (core dumped) $python_exe "$@" $args
There was an error running python

If I take away enabling the ros2 bridge extension, it works just fine.

And I’m running the python.sh file from a terminal that has sourced ROS2.

[pweids]

Found the solution after looking at some of the examples. Needed to run an update step before loading the USD file. So it would look like this

# ...
from omni.isaac.core.utils.extensions import enable_extension
enable_extension("omni.isaac.ros2_bridge")

# add the below
kit.update()

import omni
usd_path = "/isaac-sim/workspaces/blank.usd"
omni.usd.get_context().open_stage(usd_path)
# ...