GitHub user matthewblock created a discussion: Getting value of Airflow
variable within DeadlineAlert callback?
I'm doing some exploration of migrating my team from Airflow 2 to 3, and I'm
trying to convert our SLA callback code to use the new DeadlineAlert (which
seems much better so far!)
We store our alert configurations in Airflow variables because we have several
test environments and a production environment, and we need different settings
for each (e.g. which webhook to use, whether it's enabled, etc.) In our SLA
miss callback, we could use `Variable.get()` to fetch our config, but in a
DeadlineAlert callback, I'm running into issues because of `async`.
When I use `Variable.get()` within the callback, the error is ```You cannot use
AsyncToSync in the same thread as an async event loop - just await the async
function directly.```
I believe this happens because there is some async-sync bridging going on when
Airflow queries the meta database.
To solve this, I tried using `asyncio.to_thread(Variable.get, 'my_var')` but
then I get ```RuntimeError: Response read out of order! Got frame.id=16,
expect_id=17```. I'm guessing I'm running into issues with the event loop. I
tried locking the thread but couldn't get that to work either.
I also tried passing the variables to `dead.deadline` via kwargs using jinja
templates in the `AsyncCallback` class, but in the docs it says only variables
in context get rendered, so this didn't work:
```
with DAG(
...
deadline=DeadlineAlert(
reference=DeadlineReference.DAGRUN_LOGICAL_DATE,
interval=timedelta(seconds=10),
callback=AsyncCallback(
notify_teams_on_deadline_alert,
kwargs={"my_var": "{{ var.value.my_var }}"} # Doesn't get rendered
),
),
...
) as dag:
```
I'm a bit out of my depth with asyncio at this point. I know that
`SyncCallback` is planned for a future release, but has anyone gotten this to
work with `AsyncCallback`? Is there something obvious I'm supposed to be doing?
GitHub link: https://github.com/apache/airflow/discussions/56781
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