Crash when use 4 cameras simultaneously but okay when using 2 about carla HOT 9 CLOSED

The default timeout of 10 seconds might not be sufficient when using multiple cameras. Increase the timeout to give the simulator more time to process the requests

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Thank you for the quick response. Unfortunately, the error persists. I modified the following.
client.set_timeout(50.0)
The simulations simply wait 50 seconds before showing the same error.

One more "anomaly", I switch the simulation to async mode and everything works. However, this would not do since I need the synchronous mode.

from carla.

Hi,
the "time-out" error happens if Carla didn't answered.
It could be the connection, Carla crashed, Carla took too long, or everything else that could prevent a answer from the server in the timeout limit.

You can try to add some debug messages to see where the script got an error.
Did the Server still run after the time-out error?

btw. the code is hard to read because of the formatting. You can use

   ```python
    code
    ` ` `

to keep the format. (without space)

from carla.

@PatrickPromitzer Thank you for the coding quote tips. I did not know about triple ```. The github's editing tool only shows single `. I edited the code for future reading.

The UE 4 editor is running while the script is waiting for a response! After the time-out message, I can still move around in the UE 4 editor (using WASD). However, If I start the script again, the script returns the time-out message without the initial images. I think that using 4 cameras crashes the Carla server and prevents later connections. If I close the UE 4 editor and reopen it, the script still cannot find the Carla server. Does that mean the Carla server still running and the reopened UE 4 editor started another server? Since the UE 4 editor is still "functional", I really don't know where to debug. Do you have any suggestion where should I watch for a possible bug?

p/s: I start the UE 4 editor in the folder "./Unreal/CarlaUE4/CarlaUE4.uproject" after I finished build Carla from source.

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Normally, if the server crashes the unreal editor crashes, too. (maybe only on Ubuntu)
You could search if an old instance is running and close everything Carla related.
It is not a solution, but maybe something in the background is creating a problem.

You could look if your firewall is blocking something.

You could try making a package and test it with that package.

One thing that helps for me is adding "world.tick()" in between adding sensors or listeners.

You could try using one blueprint instance for each camera (just to be sure, even if should not make a difference)

You can watch your CPU/GPU usage, too.

For

camera_1.listen(lambda image: image.save_to_disk(f'{args.directory}/camera-1/{image.frame:06d}.png'))

you could call an custom function and log the function call.

with open("log_file.txt", "a") as f:    
    f.write("Function call: {0}".format(camera_name))

Maybe I come up with more ideas at a later time.

from carla.

@PatrickPromitzer Thank you so much for your suggestions. My firewall has been turned off. I do have a defined function for the callback.

I don't know what I have changed, but somehow the script works. I mark this as solved but I really don't know what was the problem.

from carla.

I found the problem. It is the sensor_tick. When I set the value too low (i.e., 0.02 for 50 fps), the simulator time-out while it works well with sensor_tick=1. I guess I need a better computer.

from carla.

The normal tickrate is 0.1, and at some point, the documentation said you should not go below 0.05

Try which rate works for you before buying new hardware.

from carla.

Yes, the document states that the simulation should not be less than 10 FPS (0.01) or the physic would get weird. But sensor_tick is the update rate of the camera, not the simulator itself.

Also, I am able to utilize sensor_tick=0.02 by adding the image into a global queue in the callback function. Then, after the world.tick(), I save the queued images. This makes the simulations not real-time anymore, but that does not matter since I only need the synthetic data.

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