@Marvin how can I fail a flow immediately if any of its tasks fail? I don't want to wait for all tasks to run. I am running tasks using .map

In Prefect, you can use the

skip_on_upstream_skip

option to fail a flow immediately if any of its tasks fail. This option, when set to

True

, will skip the execution of a task if any of its upstream tasks have failed. Here's an example of how you can use it:

from prefect import Flow, Task

class MyTask(Task):
    def run(self):
        # Your task logic here

# Create your tasks
task1 = MyTask(skip_on_upstream_skip=True)
task2 = MyTask(skip_on_upstream_skip=True)

# Create your flow
with Flow("My Flow") as flow:
    task1_result = task1()
    task2_result = task2.map(upstream_tasks=[task1_result])

In this example, if

task1

fails,

task2

will be skipped and the flow will fail immediately. However, please note that this will not stop the execution of tasks that are already running. If you want to stop the execution of all tasks immediately upon a single task failure, you might need to implement a custom solution, such as checking the state of all tasks at the start of each task and terminating the task if any have failed.

@Marvin is that setting real I'm not seeing it in the documentation

I apologize for the confusion. It appears there was a misunderstanding. The

skip_on_upstream_skip

attribute is not a valid attribute for controlling flow behavior in Prefect. In Prefect, the execution of the flow continues even if a task fails. This is by design, as Prefect is built to handle failures gracefully and continue with the flow execution as much as possible. However, you can control the behavior of your flow when a task fails by using Prefect's state handlers. You can write a custom state handler for your flow that sets the state of the entire flow to Failed as soon as any task fails. Here's an example of how you can do this:

from prefect import Flow, Task, Fail
from prefect.engine.state import Failed

class FailFastStateHandler:
    def __call__(self, task, old_state, new_state):
        if isinstance(new_state, Failed):
            raise Fail("Failing the flow because a task failed.")
        return new_state

class MyTask(Task):
    def run(self):
        # Your task logic here
        pass

with Flow('My Flow', state_handlers=[FailFastStateHandler()]) as flow:
    task = MyTask()

In this example,

FailFastStateHandler

is a state handler that checks if the new state of any task is Failed. If it is, it raises a

Fail

exception, which causes the entire flow to fail. Please note that this is a general advice and might need to be adjusted based on your specific use case.