| # Licensed to the Apache Software Foundation (ASF) under one |
| # or more contributor license agreements. See the NOTICE file |
| # distributed with this work for additional information |
| # regarding copyright ownership. The ASF licenses this file |
| # to you under the Apache License, Version 2.0 (the |
| # "License"); you may not use this file except in compliance |
| # with the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, |
| # software distributed under the License is distributed on an |
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| # KIND, either express or implied. See the License for the |
| # specific language governing permissions and limitations |
| # under the License. |
| from __future__ import annotations |
| |
| import abc |
| from typing import Any, AsyncIterator |
| |
| from airflow.utils.log.logging_mixin import LoggingMixin |
| |
| |
| class BaseTrigger(abc.ABC, LoggingMixin): |
| """ |
| Base class for all triggers. |
| |
| A trigger has two contexts it can exist in: |
| |
| - Inside an Operator, when it's passed to TaskDeferred |
| - Actively running in a trigger worker |
| |
| We use the same class for both situations, and rely on all Trigger classes |
| to be able to return the arguments (possible to encode with Airflow-JSON) that will |
| let them be re-instantiated elsewhere. |
| """ |
| |
| def __init__(self, **kwargs): |
| |
| # these values are set by triggerer when preparing to run the instance |
| # when run, they are injected into logger record. |
| self.task_instance = None |
| self.trigger_id = None |
| |
| def _set_context(self, context): |
| """ |
| This method, part of LoggingMixin, is used mainly for configuration of logging |
| for tasks, but is not used for triggers. |
| """ |
| raise NotImplementedError |
| |
| @abc.abstractmethod |
| def serialize(self) -> tuple[str, dict[str, Any]]: |
| """ |
| Returns the information needed to reconstruct this Trigger. |
| |
| :return: Tuple of (class path, keyword arguments needed to re-instantiate). |
| """ |
| raise NotImplementedError("Triggers must implement serialize()") |
| |
| @abc.abstractmethod |
| async def run(self) -> AsyncIterator[TriggerEvent]: |
| """ |
| Runs the trigger in an asynchronous context. |
| |
| The trigger should yield an Event whenever it wants to fire off |
| an event, and return None if it is finished. Single-event triggers |
| should thus yield and then immediately return. |
| |
| If it yields, it is likely that it will be resumed very quickly, |
| but it may not be (e.g. if the workload is being moved to another |
| triggerer process, or a multi-event trigger was being used for a |
| single-event task defer). |
| |
| In either case, Trigger classes should assume they will be persisted, |
| and then rely on cleanup() being called when they are no longer needed. |
| """ |
| raise NotImplementedError("Triggers must implement run()") |
| yield # To convince Mypy this is an async iterator. |
| |
| async def cleanup(self) -> None: |
| """ |
| Cleanup the trigger. |
| |
| Called when the trigger is no longer needed, and it's being removed |
| from the active triggerer process. |
| |
| This method follows the async/await pattern to allow to run the cleanup |
| in triggerer main event loop. Exceptions raised by the cleanup method |
| are ignored, so if you would like to be able to debug them and be notified |
| that cleanup method failed, you should wrap your code with try/except block |
| and handle it appropriately (in async-compatible way). |
| """ |
| |
| def __repr__(self) -> str: |
| classpath, kwargs = self.serialize() |
| kwargs_str = ", ".join(f"{k}={v}" for k, v in kwargs.items()) |
| return f"<{classpath} {kwargs_str}>" |
| |
| |
| class TriggerEvent: |
| """ |
| Something that a trigger can fire when its conditions are met. |
| |
| Events must have a uniquely identifying value that would be the same |
| wherever the trigger is run; this is to ensure that if the same trigger |
| is being run in two locations (for HA reasons) that we can deduplicate its |
| events. |
| """ |
| |
| def __init__(self, payload: Any): |
| self.payload = payload |
| |
| def __repr__(self) -> str: |
| return f"TriggerEvent<{self.payload!r}>" |
| |
| def __eq__(self, other): |
| if isinstance(other, TriggerEvent): |
| return other.payload == self.payload |
| return False |