jason810496 commented on code in PR #51056: URL: https://github.com/apache/airflow/pull/51056#discussion_r2107440538
########## providers/postgres/src/airflow/providers/postgres/triggers/postgres_cdc.py: ########## @@ -0,0 +1,125 @@ +# 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 asyncio +import datetime +from collections.abc import AsyncGenerator +from datetime import timezone + +import psycopg2 + +from airflow.hooks.base import BaseHook +from airflow.models import Variable +from airflow.triggers.base import BaseEventTrigger, TriggerEvent + + +class PostgresCDCEventTrigger(BaseEventTrigger): + """ + A trigger that waits for changes in a PostgreSQL table using polling over a timestamp/version column. + + The behavior of this trigger is as follows: + - Poll the target table using `SELECT MAX(cdc_column)`. + - Compare the result with the stored "last read" value (persisted as an Airflow Variable). + - If a new value is found (greater than last read), emit a TriggerEvent containing metadata. + - If no new value is found, sleep for `polling_interval` seconds and continue polling. + + :param conn_id: Airflow connection ID for PostgreSQL. + :param table: Name of the table to monitor. + :param cdc_column: Column representing the change timestamp or version. + :param polling_interval: Time (seconds) between polling attempts (default: 10.0). + :param state_key: Key used for persisting CDC state. If None, defaults to `{table}_cdc_last_value`. + """ + + def __init__( + self, + conn_id: str, + table: str, + cdc_column: str, + polling_interval: float = 10.0, + state_key: str | None = None, + ): + super().__init__() + self.conn_id = conn_id + self.table = table + self.cdc_column = cdc_column + self.polling_interval = polling_interval + self.state_key = state_key or f"{self.table}_cdc_last_value" + + def serialize(self) -> tuple[str, dict]: + """Serialize the trigger's configuration for persistence and reconstruction.""" + return ( + "airflow.providers.postgres.triggers.postgres_cdc.PostgresCDCEventTrigger", + { + "conn_id": self.conn_id, + "table": self.table, + "cdc_column": self.cdc_column, + "polling_interval": self.polling_interval, + "state_key": self.state_key, + }, + ) + + async def run(self) -> AsyncGenerator[TriggerEvent, None]: + """Run the asynchronous polling loop to detect new changes in the monitored table.""" + conn = BaseHook.get_connection(self.conn_id) + + while True: + try: + with psycopg2.connect( + host=conn.host, + port=conn.port, + dbname=conn.schema, + user=conn.login, + password=conn.password, + ) as pg_conn: + with pg_conn.cursor() as cursor: + cursor.execute(f"SELECT MAX({self.cdc_column}) FROM {self.table}") + result = cursor.fetchone() + max_value: datetime.datetime | None = result[0] + + if max_value is not None: Review Comment: I think we could flatten the `max_value` criteria with early return: ```python if not max_value: self.log.info("No data found in %s for column %s.", self.table, self.cdc_column) return # ... rest of logic ``` ########## providers/postgres/src/airflow/providers/postgres/triggers/postgres_cdc.py: ########## @@ -0,0 +1,125 @@ +# 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 asyncio +import datetime +from collections.abc import AsyncGenerator +from datetime import timezone + +import psycopg2 + +from airflow.hooks.base import BaseHook +from airflow.models import Variable +from airflow.triggers.base import BaseEventTrigger, TriggerEvent + + +class PostgresCDCEventTrigger(BaseEventTrigger): + """ + A trigger that waits for changes in a PostgreSQL table using polling over a timestamp/version column. + + The behavior of this trigger is as follows: + - Poll the target table using `SELECT MAX(cdc_column)`. + - Compare the result with the stored "last read" value (persisted as an Airflow Variable). + - If a new value is found (greater than last read), emit a TriggerEvent containing metadata. + - If no new value is found, sleep for `polling_interval` seconds and continue polling. + + :param conn_id: Airflow connection ID for PostgreSQL. + :param table: Name of the table to monitor. + :param cdc_column: Column representing the change timestamp or version. + :param polling_interval: Time (seconds) between polling attempts (default: 10.0). + :param state_key: Key used for persisting CDC state. If None, defaults to `{table}_cdc_last_value`. + """ + + def __init__( + self, + conn_id: str, + table: str, + cdc_column: str, + polling_interval: float = 10.0, + state_key: str | None = None, + ): + super().__init__() + self.conn_id = conn_id + self.table = table + self.cdc_column = cdc_column + self.polling_interval = polling_interval + self.state_key = state_key or f"{self.table}_cdc_last_value" + + def serialize(self) -> tuple[str, dict]: + """Serialize the trigger's configuration for persistence and reconstruction.""" + return ( + "airflow.providers.postgres.triggers.postgres_cdc.PostgresCDCEventTrigger", + { + "conn_id": self.conn_id, + "table": self.table, + "cdc_column": self.cdc_column, + "polling_interval": self.polling_interval, + "state_key": self.state_key, + }, + ) + + async def run(self) -> AsyncGenerator[TriggerEvent, None]: Review Comment: ```suggestion async def run(self) -> AsyncGenerator[TriggerEvent]: ``` ########## providers/postgres/tests/system/postgres/example_postgres_cdc_asset_watcher.py: ########## @@ -0,0 +1,97 @@ +# 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 + +from datetime import datetime, timezone + +import psycopg2 + +from airflow.hooks.base import BaseHook +from airflow.models import Variable +from airflow.providers.postgres.triggers.postgres_cdc import PostgresCDCEventTrigger +from airflow.sdk import DAG, Asset, AssetWatcher, task + +""" +Example DAG that demonstrates how to use the PostgresCDCEventTrigger. + +This DAG sets up an AssetWatcher linked to a PostgreSQL CDC trigger, which monitors changes +in a specific table based on a timestamp column (`cdc_column`). When a change is detected, it executes a task +that processes new rows and updates the Airflow Variable used to track CDC state (`state_key`). + +The state variable is configurable via `state_key`. +""" + +STATE_KEY = "my_table_cdc_last_value" + +cdc_trigger = PostgresCDCEventTrigger( + conn_id="postgres_default", + table="my_table", + cdc_column="updated_at", + polling_interval=20, + state_key=STATE_KEY, +) + +cdc_asset = Asset( + "postgres_cdc_asset", watchers=[AssetWatcher(name="postgres_cdc_watcher", trigger=cdc_trigger)] +) + +with DAG( + dag_id="example_postgres_cdc_watcher", + schedule=[cdc_asset], + catchup=False, + max_active_runs=1, +) as dag: + + @task + def extract_and_update_last_value(): + """ + Extracts new rows from the monitored table that have `updated_at` greater than the + last recorded value in Airflow Variable, then updates the Variable with the new maximum. + """ + conn = BaseHook.get_connection("postgres_default") + + with psycopg2.connect( + host=conn.host, port=conn.port, dbname=conn.schema, user=conn.login, password=conn.password + ) as pg_conn: + with pg_conn.cursor() as cursor: + last_value = Variable.get(STATE_KEY, default_var=None) Review Comment: How about having a `state_key` readonly property in `PostgresCDCEventTrigger`, so that user can get last value with: ```python last_value = Variable.get(cdc_trigger.state_key, default_var=None) ``` ########## providers/postgres/src/airflow/providers/postgres/triggers/postgres_cdc.py: ########## @@ -0,0 +1,125 @@ +# 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 asyncio +import datetime +from collections.abc import AsyncGenerator +from datetime import timezone + +import psycopg2 + +from airflow.hooks.base import BaseHook +from airflow.models import Variable +from airflow.triggers.base import BaseEventTrigger, TriggerEvent + + +class PostgresCDCEventTrigger(BaseEventTrigger): + """ + A trigger that waits for changes in a PostgreSQL table using polling over a timestamp/version column. + + The behavior of this trigger is as follows: + - Poll the target table using `SELECT MAX(cdc_column)`. + - Compare the result with the stored "last read" value (persisted as an Airflow Variable). + - If a new value is found (greater than last read), emit a TriggerEvent containing metadata. + - If no new value is found, sleep for `polling_interval` seconds and continue polling. + + :param conn_id: Airflow connection ID for PostgreSQL. + :param table: Name of the table to monitor. + :param cdc_column: Column representing the change timestamp or version. + :param polling_interval: Time (seconds) between polling attempts (default: 10.0). + :param state_key: Key used for persisting CDC state. If None, defaults to `{table}_cdc_last_value`. + """ + + def __init__( + self, + conn_id: str, + table: str, + cdc_column: str, + polling_interval: float = 10.0, + state_key: str | None = None, + ): + super().__init__() + self.conn_id = conn_id + self.table = table + self.cdc_column = cdc_column + self.polling_interval = polling_interval + self.state_key = state_key or f"{self.table}_cdc_last_value" + + def serialize(self) -> tuple[str, dict]: + """Serialize the trigger's configuration for persistence and reconstruction.""" + return ( + "airflow.providers.postgres.triggers.postgres_cdc.PostgresCDCEventTrigger", + { + "conn_id": self.conn_id, + "table": self.table, + "cdc_column": self.cdc_column, + "polling_interval": self.polling_interval, + "state_key": self.state_key, + }, + ) + + async def run(self) -> AsyncGenerator[TriggerEvent, None]: + """Run the asynchronous polling loop to detect new changes in the monitored table.""" + conn = BaseHook.get_connection(self.conn_id) + + while True: + try: + with psycopg2.connect( + host=conn.host, + port=conn.port, + dbname=conn.schema, + user=conn.login, + password=conn.password, + ) as pg_conn: + with pg_conn.cursor() as cursor: Review Comment: How about using existed `PostgresHook` to establish connection ? -- This is an automated message from the Apache Git Service. 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