Let me address your questions one by one: 1. Impact on Normal Python Code/APIs: - Your normal Python code and APIs will continue to run as they are independent of the Prefect server - The Prefect server is primarily responsible for orchestration, scheduling, and state management - Running flows will continue executing their current tasks, but won't be able to report their status back to the server - New flow runs won't be able to start until the server is back up 2. Retry/Caching/Error Handling: - Task-level retries and error handling will continue to function as they are handled at the execution level - However, flow-level orchestration features might be affected: - Task states won't be recorded in the Prefect database - Caching that depends on the Prefect server's state backend won't work - Flow-level retries that depend on server orchestration might not trigger properly 3. Handling Zombie Tasks After Server Recovery: - When your server comes back online, you might find "zombie" flows - flows stuck in a "Running" state - To handle these, you can: 1. Use Prefect's built-in heartbeat mechanism to automatically detect and mark unresponsive flows as "Failed" 2. Manually terminate zombie flows through the UI or API 3. Implement your own cleanup logic using the Prefect API Best Practices for Resilience: 1. Implement Heartbeat Monitoring:

python
from prefect import flow, task
from datetime import timedelta

@flow(flow_run_name="my-flow", timeout_seconds=3600)
def my_flow():
    # This flow will automatically fail if it can't communicate
    # with the server for more than an hour
    ...

2. Use Task Retries Independent of Server:

python
from prefect import task
from datetime import timedelta

@task(retries=3, retry_delay_seconds=60)
def my_task():
    # This task will retry locally even if server is down
    ...

3. Consider implementing your own monitoring solution to detect and handle zombie flows:

python
from prefect.client import get_client
from datetime import datetime, timedelta

async def cleanup_zombie_flows():
    client = get_client()
    flows = await client.read_flow_runs(
        flow_run_filter={"state": {"type": "RUNNING"}},
    )
    # Handle flows that have been running too long
    ...

For more details, you can refer to: - Detecting Zombie Flows Documentation - Task Retries Documentation Remember that while Prefect provides mechanisms to handle server failures gracefully, it's important to: 1. Have proper monitoring in place to detect server issues quickly 2. Implement appropriate retry and timeout mechanisms at both task and flow levels 3. Have a disaster recovery plan for your self-hosted server 4. Consider using backup servers or failover mechanisms for critical workflows