@Marvin How do you recommend running tasks concurrently, with a maximum number N of concurrent tasks within a flow

To run tasks concurrently in a Prefect flow, you can make use of Python's

asyncio

library. Here's a brief guide: 1. Define Async Tasks: Use the

@task

decorator from Prefect and define your tasks with

async def

indicating they can be run asynchronously. Example:

python
   from prefect import task
   
   @task
   async def async_task():
       # Your async code here

2. Define an Async Flow: Similarly, use the

@flow

decorator and define your flow with `async def`:

python
   from prefect import flow

   @flow
   async def async_flow():
       # Your async flow definition here

3. Concurrently Running Tasks: Within the async flow, you can use

asyncio.gather

to run tasks concurrently:

python
   import asyncio

   @flow
   async def async_flow():
       tasks_to_run = [async_task(param1), async_task(param2), ...]
       await asyncio.gather(*tasks_to_run)

Use

asyncio.gather

to run coroutines concurrently - it takes a list of coroutines or tasks and runs them concurrently. Now, if you have to limit the maximum number of concurrent tasks within a flow to a number

N

, Prefect currently doesn't provide a built-in feature for this. However, you could do this by creating your own semaphore to limit concurrency or structure your flow such that it naturally batches tasks to ensure no more than

N

run at the same time. Here's an idea of how you could implement it using a semaphore (This is not directly supported yet, but you can manually manage it):

python
import asyncio
from prefect import task, flow

sem = asyncio.Semaphore(N)  # N being the max number of concurrent tasks

@task
async def async_task():
    async with sem:
        # Your async task code here

@flow
async def async_flow():
    tasks_to_run = [async_task(param) for param in parameters_list]
    await asyncio.gather(*tasks_to_run)

asyncio.run(async_flow())

Remember that you would need to handle the semaphore logic within your tasks to ensure they acquire and release the semaphore correctly. Also note, the use of semaphores in async context is a Python feature, not specific to Prefect, and incorrect handling may introduce complexity or deadlocks. Please review Prefect's own documentation and community for newer features or patterns that may have been introduced after my last update.