Hey @Marvin, pls write me a test flow that runs 3 times the same task in parallel. If any task fail, fail the entire flow, but not until they are all completed

Let's first identify your version of Prefect to ensure accuracy in providing the right syntax and methods. Could you please specify which version of Prefect you're using: Prefect 2.x or Prefect 3.x? If not, I'll assume version 3.x for the search, as it's the latest and commonly used version.

3.x @Marvin

To run tasks in parallel and handle failures in Prefect 3.x, you can utilize parallel execution with Prefect's task workers while ensuring the overall flow only fails after all tasks have completed. Here's a conceptual flow you might create: 1. Parallel Execution: Use multiple task workers to run your tasks in parallel. 2. Failure Handling: Configure your flow to check the success or failure of each task after completion, and only mark the entire flow as failed if any task fails. Here's a basic structure for how you might set this up:

python
from prefect import flow, task
from prefect.task_runners import DaskTaskRunner
import random

# Define a sample task
@task
def my_task(x):
    if random.choice([True, False]):
        print(f"Task {x} succeeded")
    else:
        raise Exception(f"Task {x} failed")

# Define the flow
@flow(task_runner=DaskTaskRunner())
def my_flow():
    results = []
    for i in range(3):
        results.append(my_task.submit(i))
    
    # Await task completion and check results
    task_results = [result.result() for result in results]
    if any(result is None for result in task_results):  # Checking for any failed task
        raise Exception("One or more tasks failed")

my_flow()

### Important Points: - DaskTaskRunner: Enables parallel task execution. - Error Handling: After all tasks complete,

task_results

checks for any failure. - Flow Failure: If any task fails (here simulated randomly), the flow will raise an exception. For more detailed guidance, visit the Prefect documentation on running tasks in parallel and handling transactions and failures effectively. If you have any questions or need further details, feel free to ask!