Possibility of Persistent AppLauncher

[bikcrum]

Hi all,

I’m exploring ways to avoid relaunching the AppLauncher (IsaacSim GUI) repeatedly during development. Specifically, I’m trying to launch the AppLauncher once and reuse it, even as I make changes to my code.

To experiment with this, I set up a system using Ray, where I define an Actor that:

• Launches the AppLauncher
• Loads an environment based on a given env_cfg
• Instantiates a runner using a runner_cfg

The nice part is that the Ray actor process persists across multiple runs of my play.py script. This allows me to restart the script with different tasks, and it properly loads the new env_cfg and runner_cfg. Any changes I make to AppLauncher internals are reflected without restarting the simulation.

However, I'm running into a problem:
If I modify code (e.g., any cfgs), those changes do not reflect in the simulation. It seems the version of the module that was imported during the first actor initialization is cached. Even if I use importlib.reload(), the modified code is not reloaded after AppLauncher has been launched.

If I don’t launch the AppLauncher in the Ray actor (i.e., only load the env cfg, etc), the reload works just fine. So this behavior seems tied to the AppLauncher lifecycle.

Has anyone found a workaround for this? Or does the AppLauncher somehow lock module states after initialization?

Thanks.

[RandomOakForest]

Thanks for posting this. The current platform depends on the app being launched first, but the team will review this. Are you referring to this Ray? Thanks.

[bikcrum]

@RandomOakForest

Thank you for your response.

I can confirm that this issue is not because of Ray. I am trying to point out that once we launch the AppLauncher, the program does not read any changes to the modules.

# Pseudo code

file: mypackage.py
####################
class MyClass:
      def __init__(self):
           self.value = 5
####################

file: main.py
####################
import importlib
import mypackage

launch_app_launcher()

while True:
      importlib.reload(mypackage)
      myclass = mypackage.MyClass()
      print(myclass.value)   
      time.sleep(1)
####################

Now, launch the main.py. This will print 5 at a 1-second interval. Let's say you manually change the self.value to 10 from your editor in the file mypackage.py. This will still print 5 regardless of reimporting the package. However, when you print the content of the file, you can see it being updated.

On the other hand, if you don't launch the app launcher (don't call launch_app_launcher() in pseudo), the reimport package logic works fine, and I can see the updated content and update value from the module as well. It seems like AppLauncher is freezing the state of the modules.

Let me know if you have any insights regarding this.

Thank you!