Key error 'ray'

[Kostis-S-Z]

Description

In my first try of executing it, i got the following error. However, it didnt affect the execution of the simulation, so its something that I guess could be ignored? Is there a argument / parameter we can set to not get this error?

Reproduction

1. git clone
2. pip install -e .
3. flwr run .

Relevant log output

Loading project configuration... 
Success
ERROR :     Backend `ray`, is not supported. Use any of [] or add support for a new backend.
ERROR :     Unable to import module `ray`.

    To install the necessary dependencies, install `flwr` with the `simulation` extra:

        pip install -U "flwr[simulation]"
    
ERROR :     An exception occurred !! 'ray'
ERROR :     Traceback (most recent call last):
  File ".../federated-finetuning/.venv/lib/python3.12/site-packages/flwr/simulation/run_simulation.py", line 370, in _main_loop
    vce.start_vce(
  File ".../federated-finetuning/.venv/lib/python3.12/site-packages/flwr/server/superlink/fleet/vce/vce_api.py", line 337, in start_vce
    raise ex
  File ".../federated-finetuning/.venv/lib/python3.12/site-packages/flwr/server/superlink/fleet/vce/vce_api.py", line 325, in start_vce
    backend_type = supported_backends[backend_name]
                   ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
KeyError: 'ray'

Expected behavior

simulation starts with no error logs

System Info

OS: Ubuntu 24

Have you searched for similar issues before submitting this one?

• Yes, I have searched for similar issues

[WilliamLindskog]

Hi @Kostis-S-Z,

I tried to reproduce this error but I am not able to. I don't have access to Ubuntu 24, currently testing on 22.04. Can specify that in README otherwise.

Could you test if the problem still persists? I've updated some of the code and dependencies.

[Kostis-S-Z]

Oh thats interesting! I just cloned again the repo and installed everything from scratch, but the error is still there. Note however that the simulation runs with no problems! So its not a blocking / critical error. Maybe a solution is to add to the dependencies what the error suggests?

    To install the necessary dependencies, install `flwr` with the `simulation` extra:

        pip install -U "flwr[simulation]"

[Kostis-S-Z]

these are some of the installed package versions that might be relevant?

accelerate==1.4.0
bitsandbytes==0.45.0
flwr==1.15.0
flwr-datasets==0.5.0
torch==2.3.1
transformers==4.48.0
trl==0.8.1