Hi am struggling to find a standard way to handle flow state

Question

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

Christopher Boyd · Answer

Hi Dan I think notifications are what you are looking for <https docs prefect io ui notifications >

Khuyen Tran · Answer

This might be something you are looking for <https khuyentran1401 github io prefect alert >

Khuyen Tran · Answer

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

Dan Wise · Answer

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 · Answer

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 · Answer

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 · Answer

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

Khuyen Tran · Answer

gt When I deploy then run with an agent the decorator is not triggered Which version of prefect alert are you in

Khuyen Tran · Answer

gt 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 gt 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 · Answer

I m on 0 1 3 of prefect alert

Dan Wise · Answer

```def alert on failure block type AppriseNotificationBlock block name str ```

Dan Wise · Answer

This indicates block type should be e g an instance of a SlackWebhook or similar derived class

Dan Wise · Answer

According to your type hint

Dan Wise · Answer

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

Dan Wise · Answer

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

Dan Wise · Answer

This is highlighted nicely in PyCharm for instance

Dan Wise · Answer

Of course doesn t stop the code from working

Dan Wise · Answer

To fix the type hint use def alert on failure block type Type AppriseNotificationBlock block name str

Khuyen Tran · Answer

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