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Periodic ingestion of incremental data into BigQuery using Cloud Composer (Apache Airflow)

The repository showcases an orchestration workflow for ingesting incremental updates to data in BigQuery table using Apache Airflow / Cloud Composer.

Airflow / Composer DAG Design

Airflow - Incremental Updates

Explanation

The orchestration workflow (DAG) executes the following tasks in sequence:

  • Fetches configuration (specified in yaml) from Airflow data folder or local filesystem using PythonOperator (task id: load_config)
  • Creates a staging table in BQ to ingest the incremental updates using BigQueryCreateEmptyTableOperator (task id: bq_create_staging)
  • Using Dataflow template JDBC to BigQuery, the data is staged into the staging table. This task is carried out using DataflowTemplateOperator (task id: stage_data)
  • Now using BigQuery MERGE statement, the updates in the staging table are merged with the final table. This task is done using BigQueryOperator (task id: bq_merge).
  • Once the merge task completes, the staging table is deleted using BigQueryTableDeleteOperator (task id: bq_delete_staging)
  • Finally, the configuration stored in Cloud Composer / Apache Airflow environment variables is also cleaned up using PythonOperator (task id: delete_config)

Steps to run the DAG

1. Upload DAG

Upload the DAG by copying into ~/airflow/dags folder if your are using Apache Airflow or into Cloud Composer DAGS folder.

2. Create configuration

Create configuration for the job that captures the BQ and Datflow configuration parameters needed in a YAML file. Please refer to example-config.yaml in the repo for a sample configuration file.

In addition, create a BigQuery table schema file and add it to a GCS bucket / folder. Please refer to example-schema.json for a sample.

3. Upload configuration

If you are using Cloud Composer, copy the configuration file into data folder in the environemnt GCS bucket.

4. Run the DAG

If you are using Cloud Composer, you can trigger the DAG anytime using the following gcloud command:

> gcloud composer environments run <environment-name> --location <gcp-location> trigger_dag -- incremental_ingestion -c '{"file": "/home/airflow/gcs/data/example-config.yaml"}' -r <run-id>

If you are using Apache Airflow, you can trigger the same using the following airflow command:

> airflow trigger_dag incremental_ingestion -c '{"file": "/path/to/example-config.yaml"}' -r <run-id>