@Marvin I have async initialization code I need to run in the beginning of my process

async def my_init():
   ... # important initialization stuff

and my flow is also async

@flow
async def my_flow():
   ... # my flow, needs my_init() to happen once

how can I run

my_init()

before serving

my_flow()

?

async def main():
   await my_init()
   my_flow.serve('source_deployment')  # doesnt work
   #  File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 588, in _check_running
   #    raise RuntimeError('This event loop is already running')
   #  RuntimeError: This event loop is already running
   #  sys:1: RuntimeWarning: coroutine 'sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call' was never awaited
   #  sys:1: RuntimeWarning: coroutine 'Runner.start' was never awaited

if __name__ == '__main__':
   main()

?

To run your asynchronous initialization function

my_init()

before serving your asynchronous flow

my_flow

in Prefect, it's crucial to understand how to manage the event loop since you're dealing with asynchronous code. The error you're encountering (

RuntimeError: This event loop is already running

) often arises because you're trying to run another event loop within an existing one, especially when using

asyncio.run()

inside an already running loop such as the one in an interactive session or within a framework that manages its own event loop. Here's a suggested approach on how to structure your code: 1. Use

asyncio.run()

to invoke your main function when not already in an event loop. 2. Within the

main

function, invoke async functions directly using

await

.

python
import asyncio
from prefect import flow

async def my_init():
    # important initialization stuff
    print("Initialization done.")

@flow
async def my_flow():
    print("Flow started.")

async def main():
    await my_init()
    await my_flow()

if __name__ == '__main__':
    asyncio.run(main())

This method ensures that

my_init

completes before

my_flow

starts. Make sure to call

asyncio.run()

for the main entry point into your asynchronous program, which is the recommended way to run async code at the top level in most modern Python scripts. For more insights into async programming with Prefect, especially handling events and concurrency, you can refer to these resources: - Prefect 2.x Concepts: https://docs-2.prefect.io/latest/concepts/flows/ - Prefect 3.x Concurrency Limits: https://docs-3.prefect.io/3.0/develop/global-concurrency-limits These links are part of Prefect's documentation, where you can gather detailed information about running asynchronous tasks and managing concurrency in Prefect flows.

@Marvin your code doesnt serve the flow, instead it runs it once. I am running prefect 3.x

To serve your asynchronous flow using Prefect 3.x and ensure that the

my_init()

function runs before serving

my_flow

, here’s how you can structure the code: To serve a flow in Prefect 3.x, you use the

serve

method, and you need to make sure your initialization happens before the service starts. The concept of serving is to expose the flow for execution rather than executing it immediately. Here's how you can structure your code:

python
import asyncio
from prefect import flow

async def my_init():
    # Important initialization logic
    print("Initialization complete.")

@flow
async def my_flow():
    # The main flow logic
    print("Flow is running.")

async def main():
    await my_init()
    # Serve the flow for scheduled runs
    my_flow.serve(name="source_deployment")

if __name__ == '__main__':
    asyncio.run(main())  # This assumes you're not inside another running event loop

In the code above: -

my_init()

is called first, ensuring all initializations are performed. -

my_flow.serve(name="source_deployment")

serves the flow, making it available for scheduled and manual runs. The error you encountered about the event loop suggests using

asyncio.run()

, which should be called only when you're sure another event loop isn't running. If you were within an environment that already manages the event loop, you would handle this differently by integrating into the existing loop or using other methods to manage concurrent executions. You can find more details on flow serving and deployment in Prefect 3.x here: - Prefect 3.x Developing Flows - Prefect Website Example This setup ensures that your flow is adequately prepared (initialized) and then served, ready for execution as designed.

@Marvin I used your exact code. this is the resutl: C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Scripts\python.exe C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py 2024-10-14 120348.133 | DEBUG | gv.ai.common.settings&lt;module&gt;195 - Software Start Time Initialization complete. Your flow 'my-flow' is being served and polling for scheduled runs! To trigger a run for this flow, use the following command: $ prefect deployment run 'my-flow/source_deployment' You can also run your flow via the Prefect UI: https://app.prefect.cloud/account/05000528-6c7c-47f4-b36e-73d2cd749384/workspace/0963d9a7-6ea5-43f3-badb-f44a6046bc6f/deployments/deployment/<coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 441, in <module> asyncio.run(main()) # This assumes you're not inside another running event loop ^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 190, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 438, in main my_flow.serve(name="source_deployment") File "C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Lib\site-packages\prefect\flows.py", line 930, in serve loop.run_until_complete(runner.start(webserver=webserver)) File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 629, in run_until_complete self._check_running() File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 588, in _check_running raise RuntimeError('This event loop is already running') RuntimeError: This event loop is already running sys1 RuntimeWarning: coroutine 'sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call' was never awaited sys1 RuntimeWarning: coroutine 'Runner.start' was never awaited Process finished with exit code 1

Your message was too long by 508 tokens - please shorten it and try again. For reference, here's your message at the allowed limit:

I used your exact code. this is the resutl:

C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Scripts\python.exe C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py 2024-10-14 120348.133 | DEBUG | gv.ai.common.settings&lt;module&gt;195 - Software Start Time Initialization complete. Your flow 'my-flow' is being served and polling for scheduled runs! To trigger a run for this flow, use the following command: $ prefect deployment run 'my-flow/source_deployment' You can also run your flow via the Prefect UI: https://app.prefect.cloud/account/05000528-6c7c-47f4-b36e-73d2cd749384/workspace/0963d9a7-6ea5-43f3-badb-f44a6046bc6f/deployments/deployment/<coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C

@Marvin I used your exact code. this is the resutl: <coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 441, in <module> asyncio.run(main()) # This assumes you're not inside another running event loop ^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 190, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 438, in main my_flow.serve(name="source_deployment") File "C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Lib\site-packages\prefect\flows.py", line 930, in serve loop.run_until_complete(runner.start(webserver=webserver)) File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 629, in run_until_complete self._check_running() File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 588, in _check_running raise RuntimeError('This event loop is already running') RuntimeError: This event loop is already running sys1 RuntimeWarning: coroutine 'sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call' was never awaited sys1 RuntimeWarning: coroutine 'Runner.start' was never awaited Process finished with exit code 1

Your message was too long by 273 tokens - please shorten it and try again. For reference, here's your message at the allowed limit:

I used your exact code. this is the resutl:

<coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 441, in <module> asyncio.run(main()) # This assumes you're not inside another running event loop ^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 190, in run return runner.run(main) ^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\runners.py", line 118, in run return self._loop.run_until_complete(task) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\aviad\Documents\GitHub\gig

@Marvin I used your exact code. this is the resutl: <coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 441, in <module> asyncio.run(main()) # This assumes you're not inside another running event loop ^^^^^^^^^^^^^^^^^^^ ... File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 438, in main my_flow.serve(name="source_deployment") File "C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Lib\site-packages\prefect\flows.py", line 930, in serve loop.run_until_complete(runner.start(webserver=webserver)) File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 629, in run_until_complete self._check_running() File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 588, in _check_running raise RuntimeError('This event loop is already running') RuntimeError: This event loop is already running sys1 RuntimeWarning: coroutine 'sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call' was never awaited sys1 RuntimeWarning: coroutine 'Runner.start' was never awaited Process finished with exit code 1

Your message was too long by 171 tokens - please shorten it and try again. For reference, here's your message at the allowed limit:

I used your exact code. this is the resutl:

<coroutine object sync_compatible.<locals>.coroutine_wrapper.<locals>.ctx_call at 0x0000020C56BE0A40> Traceback (most recent call last): File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 441, in <module> asyncio.run(main()) # This assumes you're not inside another running event loop ^^^^^^^^^^^^^^^^^^^ ... File "C:\Users\aviad\AppData\Local\Programs\Python\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete return future.result() ^^^^^^^^^^^^^^^ File "C:\Users\aviad\Documents\GitHub\gigaverse-ai\src\gv\ai\backend_integration_service\stream_recap_flow.py", line 438, in main my_flow.serve(name="source_deployment") File "C:\Users\aviad\AppData\Local\pypoetry\Cache\virtualenvs\gv-TD9Xm0oY-py3.11\Lib\site-packages\prefect\flows.py", line 930, in serve loop.run_until_complete(r