jroachgolf84 commented on code in PR #51056: URL: https://github.com/apache/airflow/pull/51056#discussion_r2119140199
########## providers/postgres/src/airflow/providers/postgres/triggers/postgres_cdc.py: ########## @@ -0,0 +1,127 @@ +# 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 +from collections.abc import AsyncGenerator +from datetime import datetime, timezone + +from airflow.exceptions import AirflowOptionalProviderFeatureException +from airflow.providers.postgres.hooks.postgres import PostgresHook + +# Version guard for Event-driven triggers and Variable (requires Airflow >= 3.0) +try: + from airflow.sdk import Variable + from airflow.triggers.base import BaseEventTrigger, TriggerEvent +except ImportError: + raise AirflowOptionalProviderFeatureException( + "PostgresCDCEventTrigger requires Airflow >= 3.0 due to Event-driven scheduling support." + ) + + +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" + + @property + def state_key(self) -> str: + return self._state_key + + def serialize(self) -> tuple[str, dict]: + 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]: + hook = PostgresHook(postgres_conn_id=self.conn_id) + + while True: + try: + with hook.get_conn() 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 | None = result[0] + + if not max_value: + self.log.info("No data found in %s for column %s.", self.table, self.cdc_column) + return + + if max_value.tzinfo is None: + max_value = max_value.replace(tzinfo=timezone.utc) + + max_iso = max_value.isoformat() + + last_value = Variable.get(self.state_key, default=None) Review Comment: This doesn't need to change, but one thing that I did was add a `get_state` and `set_state` method that can eventually be subbed in. Right now, your `get_state` would just be a call to `Variable.get(...)`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
