@Marvin what exception should I catch when a prefect task times out such that retry_condition_fn lambda function can detect when it’s a timeout and retry

In Prefect, when a task times out, a

TimeoutError

exception is raised. To implement a retry mechanism that can detect when a task has timed out, you can use the

retry_condition_fn

option of the task. This function should check for

TimeoutError

in the state and return

True

if you want the task to retry. ### Example for Prefect 2.x: For a task in Prefect 2.x, you can define a custom retry handler like this:

python
from prefect import flow, task
from prefect.engine.state import Failed

def retry_on_timeout(task, task_run, state):
    if isinstance(state.result(), TimeoutError):
        return True
    return False

@task(retry_condition_fn=retry_on_timeout, retries=3, retry_delay_seconds=10)
def some_task():
    # task logic here

@flow
def my_flow():
    some_task()

if __name__ == "__main__":
    my_flow()

### Example for Prefect 3.x: For tasks in Prefect 3.x, the pattern is quite similar:

python
from prefect import flow, task
from prefect.exceptions import TimeoutError

def retry_on_timeout(task, task_run, state):
    try:
        state.result()
    except TimeoutError:
        return True
    return False

@task(retry_condition_fn=retry_on_timeout, retries=3, retry_delay_seconds=10)
def some_task():
    # task logic here

@flow
def my_flow():
    some_task()

if __name__ == "__main__":
    my_flow()

These custom retry handlers

retry_on_timeout

will cause the task to retry if a

TimeoutError

is encountered. For more details, you can refer to the respective documentation: - Prefect 2.x Task retries: https://docs-2.prefect.io/latest/concepts/tasks/#retry - Prefect 3.x Task retries: https://docs-3.prefect.io/3.0/develop/write-tasks/#retry

@Marvin with prefect 2.x, can I also catch custom errors with the same setup

Yes, in Prefect 2.x, you can catch and handle custom errors along with standard errors like

TimeoutError

by extending the logic in the

retry_condition_fn

. Here's a revised example that shows how you can catch both

TimeoutError

and a custom error: ### Example for Prefect 2.x with Custom Errors: Let's say you have a custom error called

MyCustomError

. You can modify the

retry_condition_fn

to handle both

TimeoutError

and

MyCustomError

.

python
from prefect import flow, task
from prefect.engine.state import Failed

# Define a custom error
class MyCustomError(Exception):
    pass

def retry_on_specific_errors(task, task_run, state):
    exception = state.result()
    if isinstance(exception, (TimeoutError, MyCustomError)):
        return True
    return False

@task(retry_condition_fn=retry_on_specific_errors, retries=3, retry_delay_seconds=10)
def some_task():
    # task logic here
    # Raise an error for demonstration purposes
    raise MyCustomError("This is a custom error")

@flow
def my_flow():
    some_task()

if __name__ == "__main__":
    my_flow()

In this example, the

retry_on_specific_errors

function will return

True

if the state result is an instance of either

TimeoutError

or

MyCustomError

, causing the task to retry. ### Explanation: -

retry_on_specific_errors

function checks whether the exception caught in the state is an instance of the specific errors you want to handle (

TimeoutError

or

MyCustomError

in this case). - The task definition uses

retry_condition_fn=retry_on_specific_errors

to specify the custom retry logic. - The task will retry up to 3 times (

retries=3

) with a delay of 10 seconds between retries (

retry_delay_seconds=10

). For more detailed information, you can refer to the Prefect 2.x documentation on task retries: https://docs-2.prefect.io/latest/concepts/tasks/#retry

@Marvin This TimeoutError isn’t getting picked up. Are you sure this is the right way to check

I apologize for any confusion. It seems there may be some nuances with catching

TimeoutError

directly in the

retry_condition_fn

. Instead of using

state.result()

, check the exception more directly. You might need to handle it within the

state

object differently depending on how Prefect records task state and exceptions. Here's an alternative way to set up the handler:

python
from prefect import flow, task
from prefect.engine.state import Failed

class MyCustomError(Exception):
    pass

def retry_on_specific_errors(task, task_run, state):
    if isinstance(state.state.result(raise_on_failure=False), (TimeoutError, MyCustomError)):
        return True
    return False

@task(retry_condition_fn=retry_on_specific_errors, retries=3, retry_delay_seconds=10)
def some_task():
    # task logic here
    raise MyCustomError("This is a custom error")

@flow
def my_flow():
    some_task()

if __name__ == "__main__":
    my_flow()

### Key Points: - Use

state.state.result(raise_on_failure=False)

to safely attempt accessing the result without raising the exception immediately. - Check your environment and logs to see how exceptions are being logged to ensure this logic captures the correct type. If issues persist, consider checking Prefect's forums or reporting on their GitHub for more community-driven insights.