Hi, am struggling to find a standard way to handle flow state changes in Prefect 2. the state handle...

Dan Wise

11/10/2022, 11:18 AM

Hi, am struggling to find a standard way to handle flow state changes in Prefect 2. the state handler approach in v1 is deprecated. I need to define a decorator I assume which applies the flow and then applies some kind of state handler on top of that. Does anyone have some code samples on how to do that please?

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Christopher Boyd

11/10/2022, 3:03 PM

Hi Dan, I think notifications are what you are looking for? https://docs.prefect.io/ui/notifications/

Khuyen Tran

11/10/2022, 4:04 PM

This might be something you are looking for: https://khuyentran1401.github.io/prefect-alert/

Khuyen Tran

11/10/2022, 4:06 PM

Right now this collection only supports alerting on failure, but we plan to support handling any states in the future

Dan Wise

11/10/2022, 4:34 PM

Thanks. I tried prefect-alert and it works fine when running as per the example directly from a script. However when I deploy then run with an agent the decorator is not triggered.

Dan Wise

11/10/2022, 4:36 PM

Also SlackWebhook uses the old incoming webhook alerts. We use messages posted via an app using the slack client so was wondering it a notification type will be created for firing messages to Slack that way

Dan Wise

11/10/2022, 4:40 PM

Also, in the alert_on_failure decorator, you define the block_type to be an object instance of a AppriseNotificationBlock but I believe you are expecting a class instance

Dan Wise

11/10/2022, 4:45 PM

And thanks @Christopher Boyd I have seen Notifications. But I was looking for a decorator much like @Khuyen Tran was referring to.

Khuyen Tran

11/10/2022, 4:49 PM

When I deploy then run with an agent the decorator is not triggered

Which version of prefect-alert are you in?

Khuyen Tran

11/10/2022, 4:52 PM

We use messages posted via an app using the slack client so was wondering it a notification type will be created for firing messages to Slack that way

You mean creating notification using something that is not a notification block?

In the alert_on_failure decorator, you define the block_type to be an object instance of a AppriseNotificationBlock but I believe you are expecting a class instance

Could you be more specific about that you mean by object instance and class instance?

Dan Wise

11/10/2022, 4:55 PM

I'm on 0.1.3 of prefect-alert

Dan Wise

11/10/2022, 4:55 PM

Copy code

def alert_on_failure(block_type: AppriseNotificationBlock, block_name: str):

Dan Wise

11/10/2022, 4:56 PM

This indicates block_type should be e.g. an instance of a SlackWebhook or similar derived class

Dan Wise

11/10/2022, 4:56 PM

According to your type hint

Dan Wise

11/10/2022, 4:57 PM

However it actually want you to pass a class instance so SlackWebhook not SlackWebhook("my-hook-name")

Dan Wise

11/10/2022, 4:57 PM

So the type hint is telling you one thing but the actuality is you want a different type passed to the hint

Dan Wise

11/10/2022, 4:58 PM

This is highlighted nicely in PyCharm for instance

Dan Wise

11/10/2022, 4:58 PM

Of course doesn't stop the code from working

Dan Wise

11/10/2022, 4:59 PM

To fix the type hint, use:def alert_on_failure(block_type:Type[AppriseNotificationBlock], block_name: str):

Khuyen Tran

11/10/2022, 7:41 PM

Thanks for the feedback. I’ll make some changes to prefect-alert and keep you updated

gratitude thank you 1

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