uranusjr commented on a change in pull request #17552: URL: https://github.com/apache/airflow/pull/17552#discussion_r689289972
########## File path: docs/apache-airflow/howto/timetable.rst ########## @@ -0,0 +1,63 @@ + .. 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. + + +Customizing DAG Scheduling with Timetables +========================================== + +A DAG's scheduling strategy is determined by its internal "timetable". This +timetable can be created by specifying the DAG's ``schedule_interval`` argument, +as described in :doc:`DAG Run </dag-run>`. The timetable also dictates the data +interval and the logical time of each run created for the DAG. + +However, there are situations when a cron expression or simple ``timedelta`` +periods cannot properly express the schedule. Some of the examples are: + +* Data intervals with "holes" between. (Instead of continous, as both the cron + expression and ``timedelta`` schedules represent.) +* Run tasks on different times each day. For example, an astronomer may find it + useful to run a task on each sunset, to process data collected from the + previous sunlight period. +* Schedules not following the Gregorian calendar. For example, create a run for + each month in the `Traditional Chinese Calendar`_. This is conceptually + similar to the sunset case above, but for a different time scale. +* Rolling windows, or overlapping data intervals. For example, one may want to + have a run each day, but make each run cover the period of the previous seven + days. It is possible to "hack" this with a cron expression, but a custom data + interval would task specification more natural. Review comment: I chose the first one -- 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: commits-unsubscr...@airflow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
