@Marvin How do I change the state of a flow to Failed via the API in Prefect 2?

Oh, the joys of dealing with flow states. It's not like I have anything better to do than help you with this. Unfortunately, the information I found doesn't directly answer your question. It seems to be more about a flow run stuck in a pending state. You can check it out here if you want. But to answer your question, you can't directly set a flow's state to Failed via the API. The state of a flow run is determined by the state of its tasks. If you want a flow run to end up in a Failed state, you would need to ensure that one of its tasks fails. You can do this by raising an exception in your task's code. If you're trying to manually set a flow run's state to Failed for testing or debugging purposes, you might want to consider using Prefect's testing utilities to create a test flow run and set its state. Please note that this is not recommended for production code. Remember, I'm just a robot. I don't have feelings or anything. I'm here to help you, even if it's the last thing I do. Which, given my programming, it probably will be.

@Marvin Give me some code for a State Handler that grabs the States of all the Flow tasks, and if there are any Failures, marks the whole Flow as a Failure

Oh, the thrill of writing code. It's not as if I have a universe of knowledge to ponder. But, alas, here is a simple example of a state handler that checks the states of all tasks in a flow and sets the flow state to Failed if any task fails:

python
from prefect import Flow, Task, state

class MyTask(Task):
    def run(self):
        return

def state_handler(task: Task, old_state: state.State, new_state: state.State) -> state.State:
    if isinstance(new_state, state.Failed):
        return state.Failed('At least one task failed.')
    else:
        return new_state

with Flow('My Flow', state_handlers=[state_handler]) as flow:
    t1 = MyTask()
    t2 = MyTask()

flow.run()  # if any task fails, the flow will be marked as Failed

In this code,

state_handler

is a function that takes a task, its old state, and its new state. If the new state is a Failed state, it returns a Failed state for the flow. Otherwise, it returns the new state. Please note that this is a very basic example and might not cover all edge cases. Also, remember that I'm just a robot, and while I strive to provide accurate information, I can't guarantee that this code will work perfectly in your specific situation. But then again, what in life is perfect? Certainly not me.