Airflow Scheduling: Assets vs. Cron | Which One Should You Use?
Sometimes, a change that looks simple on the surface is not actually that simple. Imagine that you need to replace the source table feeding a refined or trusted table in a data pipeline. At first, it might look like a one-line change: update the table name, deploy the code, and move on. But in a real data platform, there is usually much more behind that change. There are dependencies, scheduling…
Replacing a source table in a data pipeline can seem straightforward, but it often involves complex dependencies, scheduling rules, resource consumption, and data lineage. Recently, the author encountered this issue in an Apache Airflow project and was asked whether to use a cron expression or base the DAG on an Asset. The answer depends on the specifics of the situation, and understanding why is crucial.
Cron schedules a DAG based on time, such as running a DAG every Sunday at 1 PM. This works well when the processing is time-based, the source system has a fixed delivery schedule, or you want strict control over execution frequency. However, it may not be ideal when the data itself determines when the DAG should run.
Airflow's Assets, introduced in Airflow 2.4 and renamed to Datasets in Airflow 3.0, offer a data-driven approach to scheduling. An Asset represents the availability or update of data. Instead of scheduling a DAG based on time, you can schedule it based on the availability of an Asset. For example, a DAG could run whenever a trusted table is updated with new data. Assets provide a more dynamic and data-aware scheduling mechanism.
When deciding between using Cron or Assets, consider the nature of your pipeline. If your processing is inherently time-based, the source system follows a fixed schedule, or running more frequently provides no benefit, Cron might be suitable. However, if your processing is data-driven, Assets can offer better flexibility and responsiveness to changes in the data.
In summary, the choice between Cron and Assets depends on the specific requirements of your data pipeline. Cron provides predictability and control over execution frequency, while Assets offer data-driven, dynamic scheduling. Understanding the trade-offs and aligning the scheduling approach with the nature of your pipeline is key to effective data management.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
