1fanwang commented on code in PR #71387: URL: https://github.com/apache/airflow/pull/71387#discussion_r3762188299
########## providers/apache/iceberg/src/airflow/providers/apache/iceberg/triggers/iceberg.py: ########## @@ -0,0 +1,154 @@ +# 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 typing import TYPE_CHECKING, Any + +from airflow.providers.apache.iceberg.hooks.iceberg import IcebergHook +from airflow.providers.apache.iceberg.version_compat import AIRFLOW_V_3_0_PLUS + +if AIRFLOW_V_3_0_PLUS: + from airflow.triggers.base import BaseEventTrigger, TriggerEvent +else: + from airflow.triggers.base import ( # type: ignore[assignment] + BaseTrigger as BaseEventTrigger, + TriggerEvent, + ) + +if TYPE_CHECKING: + from collections.abc import AsyncIterator, Hashable + +DEFAULT_BRANCH = "main" +WATERMARK_KEY = "snapshot_id" + + +class IcebergTableSnapshotTrigger(BaseEventTrigger): + """ + Fire an event whenever an Iceberg table gains a new snapshot. + + Polls the branch head through the catalog and emits an event when it points at a + snapshot the trigger has not reported yet, which makes a table commit usable as a + scheduling signal:: + + from airflow.sdk import Asset, AssetWatcher + + orders = Asset( + "orders", + watchers=[ + AssetWatcher( + name="orders_commits", + trigger=IcebergTableSnapshotTrigger(table="sales.orders"), + ) + ], + ) + + + @dag(schedule=[orders]) + def downstream(): ... + + Triggers sharing a catalog connection, branch and poll interval share one poll loop, + so watching many tables in a catalog does not open a connection per table. + + :param table: Fully-qualified table name, ``namespace.table``. Nested namespaces are + written as ``a.b.table``. + :param iceberg_conn_id: Connection holding the catalog URI and credentials. + :param branch: Branch or tag to watch. Defaults to ``main``. + :param poll_interval: Seconds between polls. + :param last_seen_snapshot_id: Snapshot already reported. Leave unset to treat the + current head as the first event. + """ + + def __init__( + self, + *, + table: str, + iceberg_conn_id: str = IcebergHook.default_conn_name, + branch: str = DEFAULT_BRANCH, + poll_interval: float = 60, + last_seen_snapshot_id: int | None = None, + **kwargs: Any, + ) -> None: + super().__init__(**kwargs) + if "." not in table: + raise ValueError(f"Expected a fully-qualified table name (namespace.table), got: {table!r}") + self.table = table + self.iceberg_conn_id = iceberg_conn_id + self.branch = branch + self.poll_interval = poll_interval + self.last_seen_snapshot_id = last_seen_snapshot_id + + def serialize(self) -> tuple[str, dict[str, Any]]: + return ( + "airflow.providers.apache.iceberg.triggers.iceberg.IcebergTableSnapshotTrigger", + { + "table": self.table, + "iceberg_conn_id": self.iceberg_conn_id, + "branch": self.branch, + "poll_interval": self.poll_interval, + "last_seen_snapshot_id": self.last_seen_snapshot_id, + }, + ) + + def shared_stream_key(self) -> Hashable | None: + """Group triggers that can be served by a single poll of the same catalog.""" + return (self.iceberg_conn_id, self.branch, self.poll_interval) + + def _head_snapshot_id(self) -> int | None: + """Return the snapshot the branch points at, or None if the branch does not exist.""" + table = IcebergHook(self.iceberg_conn_id).load_table(self.table) + if ref := table.metadata.refs.get(self.branch): + return ref.snapshot_id + return None + + async def run(self) -> AsyncIterator[TriggerEvent]: + # serialize() is captured once when the trigger row is created, so a value mutated on + # self is lost when the triggerer restarts and the current head would be re-emitted as + # a new commit. The watermark survives that; the kwarg only seeds the first run. + # getattr because asset_state_store postdates the Airflow versions this provider supports. + store = getattr(self, "asset_state_store", None) + if store is not None: + try: + stored = await asyncio.to_thread(store.get, WATERMARK_KEY) + except ValueError: + # Several assets watch this trigger, so there is no single cursor to keep. Review Comment: Because the [get()](https://github.com/apache/airflow/blob/eeeaa0c23d878a12d80cbf07792736f59acb5da8/task-sdk/src/airflow/sdk/execution_time/context.py#L902-L904) delegates to [_single_accessor()](https://github.com/apache/airflow/blob/eeeaa0c23d878a12d80cbf07792736f59acb5da8/task-sdk/src/airflow/sdk/execution_time/context.py#L893-L897), which raises unless exactly one asset is behind them. In the triggerer that count is the number of assets watching this trigger, so I think the only way to hit it is more than one. But I get that the catch is too broad here, how about replacing it with https://github.com/apache/airflow/pull/71460 -- 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]
