https://prefect.io
Join Slack
Hey guys there a reason for signals (`FAIL`, `PrefectStateSignal`, `PrefectSignal`) inherit from `B...
# ask-community
f
Hey guys there a reason for signals (
FAIL
, 
PrefectStateSignal
, 
PrefectSignal
) inherit from 
BaseException
instead of 
Exception
?
Sorry to bump it, is because i faced some issues using:
Copy code
try:
    ...
except Exception as err:
    pass
and raising fail signal it was not being catched.
a
what problem are you trying to solve?
you don't need to use try/except necessarily when you use Prefect, signals were needed in v1 to do things like skipping some tasks, raising a retry signal to cause a rerun of something or pausing the execution in some other way. once you migrate to v2, you can use native python so signals won't be required
internally in v1 we are using those signals to bypass all other exception handling since they are signals not actual errors
but those shouldn’t be caught unless you want to use them e.g. raise SKIP or RETRY signal
f
@Anna Geller Thanks for the answer (i using v1), basically my usage is i have a task lets say with 3 retries. If is the last retry (before raise FAIL signal again), i need to send a e-mail to notify the interested parties, so inside my task i raise SIGNAL and catch them in the 
except
statement, that was the cause of this question.
and of course if is last time i send the email and then raise the signal 😄
a
Copy code
import pendulum
from prefect.engine.signals import RETRY
import awswrangler as wr

def check_if_file_arrived_in_s3():
    return wr.s3.does_object_exist("<s3://bucket/example_file.csv>")

@task
def s3_sensor(**kwargs):
    bool_s3_object_arrived = check_if_file_arrived_in_s3()
    if bool_s3_object_arrived is False:
        raise RETRY(
            "File not available yet, retrying in 20 seconds.",
            start_time=pendulum.now().add(seconds=20),
        )
❤️ 1
3 Views
Open in Slack
PreviousNext
Powered by

Prefect Community

Bring your towel and join one of the fastest growing data communities. Welcome to our second-generation open source orchestration platform, a completely rethought approach to dataflow automation.

Powered by