@Marvin Execution was cancelled by the runtime environment. when using asyncio

The error "Execution was cancelled by the runtime environment" when using asyncio in Prefect can arise from several issues related to task execution and infrastructure. Here's a concise overview of potential causes and solutions: 1. Infrastructure Issues: If the infrastructure does not support cancellation, or if the infrastructure associated with the run cannot be found or has already been terminated, the runtime environment may cancel the execution. Ensure that your infrastructure (e.g., Docker, Kubernetes) supports the cancellation of tasks. 2. Concurrency and Asyncio: If you're using async tasks, make sure that the asyncio event loop is correctly managed. Issues can arise if tasks are not awaited properly or if the event loop is interrupted unexpectedly. 3. Process Pool and Forking: On Linux, using a

ProcessPoolExecutor

with the

fork

start method can lead to hangs or cancellations. Switching to the

spawn

start method might resolve these issues. This is particularly relevant if your tasks involve multiprocessing. 4. Error Handling: Implement proper error handling in your tasks and flows to catch exceptions that might lead to cancellations. This includes handling

CancelledError

in asyncio tasks. 5. Prefect Version: Ensure you are using a compatible version of Prefect. Some issues might be version-specific, and upgrading could resolve underlying bugs. For more detailed information, you can refer to these resources: - Prefect Cancellation Documentation - GitHub issues discussing similar scenarios: - Workflow hangs with ProcessPool - Execution cancelled by runtime environment If you have specific code snippets or setups that are causing issues, reviewing those can help pinpoint the exact cause.