When running any Orion flow, I'm getting the error: "cannot import name 'ThreadedChildWatcher' from 'asyncio' " - how to fix it?

[anna_geller]

Problem

This problem occurs when running Orion on Windows. At the time of writing (early March 2022), you can’t run Orion on Windows.

Solution

As a workaround, you can install Orion on a subsystem for Linux (WSL) or spin up Orion on a Linux VM.

Slack discussion

View in #prefect-community on Slack

@Ayah_Safeen: Hello All…
I was checking the new open-source engine “Orion”, but when I run the code I get the following error on the import statement from prefect import flow

cannot import name 'ThreadedChildWatcher' from 'asyncio'

The code :

from prefect import flow
@flow
def common_flow(config: dict):
    print("I am a subgraph that shows up in lots of places!")
    intermediate_result = 42
    return intermediate_result

@flow
def main_flow():

    data = common_flow(config={})

# run the flow
flow_state = main_flow()

@Anna_Geller: What Python version do you use? What’s your Orion version?

prefect --version

Can you import this function without errors?

from asyncio import get_running_loop

Often reinstalling Orion in a new virtual environment and resetting the DB helps in similar cases - you can:
• delete the database file ~/.prefect/orion.db.
• reset the database with the CLI command prefect orion database reset
• and then restart orion with prefect orion start

@Ayah_Safeen: • python version Python 3.10.1
• from asyncio import get_running_loop is running as well without any errors
• there is no orion.db file in venv\Lib\site-packages\prefect directory
• Finally I get the same error mentioned in the previous message when I run those commands prefect orion database reset
prefect orion start

@Anna_Geller: I believe the DB file is always located in ~/.prefect/orion.db regardless of whether you install Orion globally or in a virtual environment

@Ayah_Safeen: Hi, I installed it on ubuntu env instead of windows, and worked as well