jroachgolf84 commented on code in PR #67299: URL: https://github.com/apache/airflow/pull/67299#discussion_r3357040163
########## airflow-core/docs/core-concepts/asset-store.rst: ########## @@ -0,0 +1,247 @@ + .. 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. + +.. _concepts:asset-store: + +.. spelling:word-list:: + + subscripted + subscripting + +Asset Store +=========== + +.. versionadded:: 3.3 + +Asset store is a persistent key/value store scoped to an *asset*, independent of any particular DAG run. Unlike :doc:`task store </core-concepts/task-store>`, which is tied to a single task instance, asset store persists across runs and is logically owned by the asset itself. It is the natural home for cross-run metadata such as watermarks, incremental-load cursors, and per-asset configuration. + +Asset store is accessed through the task context via ``context["asset_store"]``. + + +When is ``asset_store`` available? +------------------------------------ + +When using asset store within a task, ``context["asset_store"]`` is populated for **concrete** :class:`~airflow.sdk.definitions.asset.Asset` inlets and outlets. A task must declare at least one concrete inlet or outlet for ``asset_store`` to contain any entries. + +If using asset store in a ``BaseEventTrigger``, the ``self.asset_store`` parameter can be used within the ``BaseEventTrigger``. It can be subscripted in the same way that ``context["asset_store"]`` can be. + +.. warning:: + + **Outlets-only tasks**: if a task declares only ``outlets`` (no ``inlets``), ``context["asset_store"][my_asset]`` may raise a ``KeyError`` at runtime. The workaround is to declare the asset in **both** ``inlets`` and ``outlets``. + + .. code-block:: python + + # my_asset defined above ... + + + @task(inlets=[my_asset], outlets=[my_asset]) + def write_asset(**context): + context["asset_store"][my_asset].set("watermark", "2024-01-01") + + This known issue will be resolved in a future release. + + +Accessing asset store using ``context`` +--------------------------------------- + +An asset can be brought into "scope" (for lack of a better phrase) by including it in ``inlets`` (or both ``inlets`` and ``outlets``). Then subscript ``context["asset_store"]`` with the asset object to retrieve the asset store. + +.. code-block:: python + + from airflow.sdk import Asset, DAG, task + + my_asset = Asset("my_data", uri="s3://bucket/my_data") + + with DAG("example_asset_store", schedule=None): + + @task(inlets=[my_asset], outlets=[my_asset]) + def process(**context): + asset_store = context["asset_store"][my_asset] + watermark = asset_store.get("watermark") + asset_store.set("watermark", "2024-06-01") + +To see asset store in-action in a real DAG, checkout the DAG in `example_asset_store.py <https://github.com/apache/airflow/blob/main/airflow-core/src/airflow/example_dags/example_asset_store.py>`_. + +Accessing asset store in a ``BaseEventTrigger`` +----------------------------------------------- + +When building Triggers used for asset "watching", asset store can be retrieved using the ``self.asset_store`` attribute. + +.. code-block:: python + + from airflow.sdk import Asset, BaseEventTrigger, TriggerEvent + from collections.abc import AsyncIterator + + + class GenericEventTrigger(BaseEventTrigger): + ... + + async def run(self) -> AsyncIterator[TriggerEvent]: + """Logic that fires a TriggerEvent.""" + my_data = Asset(name="my_data") + asset_store = self.asset_store[my_data] + watermark = asset_store.get("watermark") + asset_store.set("watermark", "2024-06-01") + +In the example above, ``my_data`` is created using the ``name`` However, the ``uri`` can also be used: + +.. code-block:: python + + from airflow.sdk import Asset, BaseEventTrigger, TriggerEvent + from collections.abc import AsyncIterator + + + class GenericEventTrigger(BaseEventTrigger): + ... + + async def run(self) -> AsyncIterator[TriggerEvent]: + """Logic that fires a TriggerEvent.""" + my_data = Asset(uri="s3://bucket/my_data") + asset_store = self.asset_store[my_data] + watermark = asset_store.get("watermark") + asset_store.set("watermark", "2024-06-01") Review Comment: Resolved in next commit. -- This is an automated message from the Apache Git Service. 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