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<@ULVA73B9P> Send messages to Slack via automation...
# ask-marvin
c
@Marvin Send messages to Slack via automation when a flow needs to retry
m
Certainly, you can automate the sending of Slack messages when a flow needs to retry in Prefect using the 
prefect-slack
integration. Here are the key steps: 1. Set Up Slack App: - Create and set up a Slack App in your workspace through the Slack API. - Generate a Webhook URL for sending messages. 2. Save Slack Credentials in a Block: - Use the 
SlackWebhook
from 
prefect-slack
to save your webhook URL as a block:
Copy code
python
     from prefect_slack import SlackWebhook

     SlackWebhook(url="YOUR_WEBHOOK_URL").save("slack-webhook-block")
3. Automate Slack Notifications: - Use your saved block to send messages in your flow function. Here’s an example:
Copy code
python
   from prefect import flow, task
   from prefect_slack import send_chat_message, SlackWebhook

   @task(retries=3, retry_delay_seconds=10)
   def potentially_failing_task():
       # Simulate task logic that may fail
       if some_condition:
           raise Exception("Task failed, retrying...")

   @flow
   def example_flow():
       slack_webhook = SlackWebhook.load("slack-webhook-block")
       try:
           potentially_failing_task()
       except Exception as e:
           send_chat_message(
               slack_credentials=slack_webhook,
               text=f"Task failed with error: {e}",
               channel="#your-channel"
           )
           raise

   example_flow()
### Full Example 1. Saving Credentials Script:
Copy code
python
   from prefect_slack import SlackWebhook

   SlackWebhook(url="YOUR_WEBHOOK_URL").save("slack-webhook-block")
2. Flow Script with Message on Retry:
Copy code
python
   from prefect import flow, task
   from prefect_slack import send_chat_message, SlackWebhook

   @task(retries=3, retry_delay_seconds=10)
   def potentially_failing_task():
       # Simulate task logic that may fail
       if some_condition:
           raise Exception("Task failed, retrying...")

   @flow
   def example_flow():
       slack_webhook = SlackWebhook.load("slack-webhook-block")
       try:
           potentially_failing_task()
       except Exception as e:
           send_chat_message(
               slack_credentials=slack_webhook,
               text=f"Task failed with error: {e}",
               channel="#your-channel"
           )
           raise  # Re-raise to ensure proper flow handling

   if __name__ == "__main__":
       example_flow()
### Useful Links: - Prefect Slack Integration Documentation - Example Flow With this setup, anytime a task in your flow fails and retries, you'll get a Slack notification. Keep in mind to replace placeholders like 
"YOUR_WEBHOOK_URL"
and 
"#your-channel"
with your actual Slack Webhook URL and desired Slack channel, respectively. Hopefully, this brings some small relief in your mundane existence.
n
@Marvin maybe an 
on_failure
hook would be nice as well no?
m
Absolutely, utilizing an 
on_failure
hook provides a cleaner and more modular approach to handle tasks and notify when failures occur. Prefect's 
Task
objects have several lifecycle hooks that you can use, such as 
on_failure
. Here's how you can integrate an 
on_failure
notification to Slack within your flow: 1. Set Up Slack App (same as previous steps if not already done). 2. Save Slack Credentials (same as previous steps if not already done). 3. Define a Failure Hook: Define a function that sends a Slack message. This function will be called on task failure. 4. Attach the Hook to Tasks: Use the 
on_failure
hook parameter to bind your notification function. ### Example: 1. Saving Credentials Script:
Copy code
python
   from prefect_slack import SlackWebhook

   SlackWebhook(url="YOUR_WEBHOOK_URL").save("slack-webhook-block")
2. Flow Script with 
on_failure
Hook:
Copy code
python
   from prefect import flow, task
   from prefect_slack import send_chat_message, SlackWebhook
   from prefect.engine.task_hooks import failure_hook

   def notify_slack(context):
       """
       Function to send a notification message to Slack on task failure.
       """
       slack_webhook = SlackWebhook.load("slack-webhook-block")
       send_chat_message(
           slack_credentials=slack_webhook,
           text=f"Task {context.get('task_name')} failed with error: {context.get('exception')}",
           channel="#your-channel"
       )

   @task(retries=3, retry_delay_seconds=10, on_failure=notify_slack)
   def potentially_failing_task():
       import random
       # Simulating task logic that may randomly fail
       if random.choice([True, False]):
           raise Exception("Task failed, retrying...")

   @flow
   def example_flow():
       potentially_failing_task()

   if __name__ == "__main__":
       example_flow()
In this script: - The 
notify_slack
function is defined to send a Slack message when a task fails. - This function is attached to the 
on_failure
hook of the 
potentially_failing_task
. - The flow 
example_flow
includes the task which will automatically notify Slack upon failure. ### Useful Links: - Prefect Slack Integration Documentation - Example Flow This approach provides superior modularity and ensures that your notification logic is separated from your task logic. This should fit nicely into your disaster-prone workflows... I mean, life.
c
Thanks Nate. We have that. I removed a slack webhook from our code thinking the automation would pick up the retry logic, but it didnt'
n
automation would pick up the retry logic
hmm what do you mean?
c
In the automation page of the UI, we setup a Slack channel for failures, etc.
I attempted to add the retry state to that
n
did you set the flow run state to 
AwaitingRetry
?
to clarify, if you want to only send a notification after all retries are exhaused, i would select 
Failed
as the state to notify on since it wont actually enter 
Failed
until it fails more than you have retries
c
Yes, it sends a notification after it fails 3 times
(the number of retries).
n
gotcha, yeah it should work if you select 
Failed
as the state to notify on (without using the webhook in your flow code)
c
I did not try AwaitingRetry
n
if you selected awaitingretry, it would trigger each time you start to retry
since we go 
Running
-> 
AwaitingRetry
-> 
Running
etc
👍 1
c
Perfect
t
Is the 
Retrying
state only used when you manually retry a failed flow from the UI @Nate?
c
Updated. We will see if it works sooner or later
n
@Thomas DeBroux 
Retrying
is just an alias for 
Running
, which also is set in the SDK https://github.com/prefecthq/prefect/blob/main/src/prefect/task_engine.py#L373-L383 what i linked is the new engine, which is just a less complex way to express what we do in 
prefect
latest on PyPI, same idea
👍 2
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