kaxil commented on a change in pull request #20150:
URL: https://github.com/apache/airflow/pull/20150#discussion_r765221046
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File path: docs/apache-airflow/concepts/deferring.rst
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@@ -109,13 +109,13 @@ There's also some design constraints to be aware of:
* The ``run`` method *must be asynchronous* (using Python's asyncio), and
correctly ``await`` whenever it does a blocking operation.
* ``run`` must ``yield`` its TriggerEvents, not return them. If it returns
before yielding at least one event, Airflow will consider this an error and
fail any Task Instances waiting on it. If it throws an exception, Airflow will
also fail any dependent task instances.
-* A Trigger *must be able to run in parallel* with other copies of itself.
This can happen both when two tasks defer based on the same trigger, and also
if a network partition happens and Airflow re-launches a trigger on a separated
machine.
+* You must assume that duplicates of your trigger instance may run
simultaneously. This can happen if a network partition happens and Airflow
re-launches a trigger on a separated machine.
* When events are emitted, and if your trigger is designed to emit more than
one event, they *must* contain a payload that can be used to deduplicate events
if the trigger is being run in multiple places. If you only fire one event, and
don't want to pass information in the payload back to the Operator that
deferred, you can just set the payload to ``None``.
-* A trigger may be suddenly removed from one process and started on a new one
(if partitions are being changed, or a deployment is happening). You may
provide an optional ``cleanup`` method that gets called when this happens.
+* A trigger may be suddenly removed from one triggerer service and started on
a new one (e.g. if network partitions are being changed, or a deployment is
happening). If desired you may implement ``cleanup`` method that is always
called after ``run`` whether the trigger exits cleanly or otherwise.
Review comment:
```suggestion
* A trigger may be suddenly removed from one triggerer service and started
on a new one (e.g. if network partitions (Subnets for example) are being
changed, or a deployment is happening). If desired you may implement
``cleanup`` method that is always called after ``run`` whether the trigger
exits cleanly or otherwise.
```
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