Running a Data Analytics DAG in Google Cloud Using Data from AWS

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This tutorial is a modification of Running a Data Analytics DAG in Google Cloud that shows how to connect your Cloud Composer environment to Amazon Web Services to utilize data stored there. It shows how to use Cloud Composer to create an Apache Airflow DAG (workflow). The DAG joins data from a BigQuery public dataset and a CSV file stored in an Amazon Web Services (AWS) S3 bucket and then runs a Dataproc Serverless batch job to process the joined data.

The BigQuery public dataset in this tutorial is ghcn_d, an integrated database of climate summaries across the globe. The CSV file contains information about the dates and names of US holidays from 1997 to 2021.

The question we want to answer using the DAG is: "How warm was it in Chicago on Thanksgiving for the past 25 years?"

Objectives

  • Create a Cloud Composer environment in the default configuration
  • Create a bucket in AWS S3
  • Create an empty BigQuery dataset
  • Create a new Cloud Storage bucket
  • Create and run a DAG that includes the following tasks:
    • Load an external dataset from S3 to Cloud Storage
    • Load an external dataset from Cloud Storage to BigQuery
    • Join two datasets in BigQuery
    • Run a data analytics PySpark job
  • Clean up the project

Before you begin

Manage permissions in AWS

  1. Create an AWS account
  2. Follow the "Creating policies with the visual editor section" of the Creating IAM Policies AWS tutorial to create a customized IAM policy for AWS S3 with the following configuration:

    • Service: S3
    • ListAllMyBuckets (s3:ListAllMyBuckets), for viewing your S3 bucket
    • CreateBucket (s3:CreateBucket), for creating a bucket
    • PutBucketOwnershipControls (s3:PutBucketOwnershipControls), for creating a bucket
    • ListBucket (s3:ListBucket), for granting permission to list objects in a S3 bucket
    • PutObject (s3:PutObject), for uploading files to a bucket
    • GetBucketVersioning (s3:GetBucketVersioning), for deleting an object in a bucket
    • DeleteObject (s3:DeleteObject), for deleting an object in a bucket
    • ListBucketVersions (s3:ListBucketVersions), for deleting a bucket
    • DeleteBucket (s3:DeleteBucket), for deleting a bucket
    • Resources: Choose "Any" next to "bucket" and "object" to grant permissions to any resources of that type.
    • Tag: None
    • Name: TutorialPolicy

    Refer to the list of actions supported in Amazon S3 for more information about each configuration found above.

  3. Add the TutorialPolicy IAM policy to your identity

Manage permissions in Google Cloud

  1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.
  2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  3. Make sure that billing is enabled for your Cloud project. Learn how to check if billing is enabled on a project.

  4. Enable the Dataproc, Composer, BigQuery, Storage APIs.

    Enable the APIs

  5. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

    Go to project selector

  6. Make sure that billing is enabled for your Cloud project. Learn how to check if billing is enabled on a project.

  7. Enable the Dataproc, Composer, BigQuery, Storage APIs.

    Enable the APIs

  8. Grant the following roles to manage Cloud Composer environments and environment buckets
    • Composer > Environment and Storage Object Administrator
    • IAM > Service Account User
  9. Grant the following role to create a BigQuery dataset
    • BigQuery > Data Owner
  10. Grant the following role to create a Cloud Storage bucket:
    • Storage > Admin

Create and prepare your Cloud Composer environment

  1. Create a Cloud Composer environment:
    1. Choose a US based compute region
    2. Choose the latest Cloud Composer version
  2. Grant the following roles to the service account used in your Cloud Composer environment in order for the Airflow workers to successfully run DAG tasks
    1. BigQuery User
    2. BigQuery Data Owner
    3. Service Account User
    4. Dataproc Editor
    5. Dataproc Worker
  1. Install the apache-airflow-providers-amazon PyPI dependency in your Cloud Composer environment. Refer to the appropriate Airflow constraints file to check for compatibility if you want to specify a specific version.
  2. Create an empty BigQuery dataset with the following parameters
    1. Name: holiday_weather
    2. Region: US
  3. Create a new Cloud Storage bucket in the US multiregion
  4. Run the following command to enable private Google access on the default subnet in the region where you would like to run Dataproc Serverless to fulfill networking requirements. We recommend using the same region as your Cloud Composer environment.

    gcloud compute networks subnets update default \
        --region DATAPROC_SERVERLESS_REGION \
        --enable-private-ip-google-access
    
  1. Create an S3 bucket with default settings in your preferred region.

Connect to AWS from Cloud Composer

  1. Get your AWS access key ID and secret access key
  2. Add your AWS S3 connection using the Airflow UI
    1. Go to Admin > Connections
    2. Create a new connection with the following configuration:
      • Connection Id: aws_s3_connection
      • Connection Type: Amazon S3
      • Extras: {"aws_access_key_id":"your_aws_access_key_id", "aws_secret_access_key": "your_aws_secret_access_key"}

Running the DAG

Data processing using Dataproc Serverless

Explore the example PySpark Job

The code shown below is an example PySpark job that converts temperature from tenths of a degree in Celsius to degrees celsius. This job will convert temperature data from the dataset into a different format.

import sys


from py4j.protocol import Py4JJavaError
from pyspark.sql import SparkSession
from pyspark.sql.functions import col


if __name__ == "__main__":
    BUCKET_NAME = sys.argv[1]
    READ_TABLE = sys.argv[2]
    WRITE_TABLE = sys.argv[3]

    # Create a SparkSession, viewable via the Spark UI
    spark = SparkSession.builder.appName("data_processing").getOrCreate()

    # Load data into dataframe if READ_TABLE exists
    try:
        df = spark.read.format("bigquery").load(READ_TABLE)
    except Py4JJavaError as e:
        raise Exception(f"Error reading {READ_TABLE}") from e

    # Convert temperature from tenths of a degree in celsius to degrees celsius
    df = df.withColumn("value", col("value") / 10)
    # Display sample of rows
    df.show(n=20)

    # Write results to GCS
    if "--dry-run" in sys.argv:
        print("Data will not be uploaded to BigQuery")
    else:
        # Set GCS temp location
        temp_path = BUCKET_NAME

        # Saving the data to BigQuery using the "indirect path" method and the spark-bigquery connector
        # Uses the "overwrite" SaveMode to ensure DAG doesn't fail when being re-run
        # See https://spark.apache.org/docs/latest/sql-data-sources-load-save-functions.html#save-modes
        # for other save mode options
        df.write.format("bigquery").option("temporaryGcsBucket", temp_path).mode(
            "overwrite"
        ).save(WRITE_TABLE)
        print("Data written to BigQuery")

Upload the PySpark file to Cloud Storage

To upload the PySpark file and the dataset stored in holidays.csv:

  1. Save data_analytics_process.py to your local machine

  2. In the Google Cloud console go to the Cloud Storage browser page:

    Go to Cloud Storage browser

  3. Click the name of the bucket you created earlier

  4. In the Objects tab for the bucket, click the Upload files button, select data_analytics_process.py in the dialog that appears, and click Open

Upload the CSV file to AWS S3

To upload the holidays.csv file:

  1. Save holidays.csv on your local machine
  2. Follow the AWS guide to upload the file to your bucket

Data analytics DAG

Explore the example workflow

The workflow uses multiple operators to transform and unify the data:

import datetime

from airflow import models
from airflow.providers.google.cloud.operators import dataproc
from airflow.providers.google.cloud.operators.bigquery import BigQueryInsertJobOperator
from airflow.providers.google.cloud.transfers.gcs_to_bigquery import (
    GCSToBigQueryOperator,
)
from airflow.providers.google.cloud.transfers.s3_to_gcs import S3ToGCSOperator
from airflow.utils.task_group import TaskGroup

PROJECT_NAME = "{{var.value.gcp_project}}"
REGION = "{{var.value.gce_region}}"

# BigQuery configs
BQ_DESTINATION_DATASET_NAME = "holiday_weather"
BQ_DESTINATION_TABLE_NAME = "holidays_weather_joined"
BQ_NORMALIZED_TABLE_NAME = "holidays_weather_normalized"

# Dataproc configs
BUCKET_NAME = "{{var.value.gcs_bucket}}"
PYSPARK_JAR = "gs://spark-lib/bigquery/spark-bigquery-latest_2.12.jar"
PROCESSING_PYTHON_FILE = f"gs://{BUCKET_NAME}/data_analytics_process.py"

# S3 configs
S3_BUCKET_NAME = "{{var.value.s3_bucket}}"

BATCH_ID = "data-processing-{{ ts_nodash | lower}}"  # Dataproc serverless only allows lowercase characters
BATCH_CONFIG = {
    "pyspark_batch": {
        "jar_file_uris": [PYSPARK_JAR],
        "main_python_file_uri": PROCESSING_PYTHON_FILE,
        "args": [
            BUCKET_NAME,
            f"{BQ_DESTINATION_DATASET_NAME}.{BQ_DESTINATION_TABLE_NAME}",
            f"{BQ_DESTINATION_DATASET_NAME}.{BQ_NORMALIZED_TABLE_NAME}",
        ],
    },
    "environment_config": {
        "execution_config": {
            "service_account": "{{var.value.dataproc_service_account}}"
        }
    },
}

yesterday = datetime.datetime.combine(
    datetime.datetime.today() - datetime.timedelta(1), datetime.datetime.min.time()
)

default_dag_args = {
    # Setting start date as yesterday starts the DAG immediately when it is
    # detected in the Cloud Storage bucket.
    "start_date": yesterday,
    # To email on failure or retry set 'email' arg to your email and enable
    # emailing here.
    "email_on_failure": False,
    "email_on_retry": False,
}

with models.DAG(
    "s3_to_gcs_dag",
    # Continue to run DAG once per day
    schedule_interval=datetime.timedelta(days=1),
    default_args=default_dag_args,
) as dag:

    s3_to_gcs_op = S3ToGCSOperator(
        task_id="s3_to_gcs",
        bucket=S3_BUCKET_NAME,
        gcp_conn_id="google_cloud_default",
        aws_conn_id="aws_s3_connection",
        dest_gcs=f"gs://{BUCKET_NAME}",
    )

    create_batch = dataproc.DataprocCreateBatchOperator(
        task_id="create_batch",
        project_id=PROJECT_NAME,
        region=REGION,
        batch=BATCH_CONFIG,
        batch_id=BATCH_ID,
    )

    load_external_dataset = GCSToBigQueryOperator(
        task_id="run_bq_external_ingestion",
        bucket=BUCKET_NAME,
        source_objects=["holidays.csv"],
        destination_project_dataset_table=f"{BQ_DESTINATION_DATASET_NAME}.holidays",
        source_format="CSV",
        schema_fields=[
            {"name": "Date", "type": "DATE"},
            {"name": "Holiday", "type": "STRING"},
        ],
        skip_leading_rows=1,
        write_disposition="WRITE_TRUNCATE",
    )

    with TaskGroup("join_bq_datasets") as bq_join_group:

        for year in range(1997, 2022):
            BQ_DATASET_NAME = f"bigquery-public-data.ghcn_d.ghcnd_{str(year)}"
            BQ_DESTINATION_TABLE_NAME = "holidays_weather_joined"
            # Specifically query a Chicago weather station
            WEATHER_HOLIDAYS_JOIN_QUERY = f"""
            SELECT Holidays.Date, Holiday, id, element, value
            FROM `{PROJECT_NAME}.holiday_weather.holidays` AS Holidays
            JOIN (SELECT id, date, element, value FROM {BQ_DATASET_NAME} AS Table
            WHERE Table.element="TMAX" AND Table.id="USW00094846") AS Weather
            ON Holidays.Date = Weather.Date;
            """

            # For demo purposes we are using WRITE_APPEND
            # but if you run the DAG repeatedly it will continue to append
            # Your use case may be different, see the Job docs
            # https://cloud.google.com/bigquery/docs/reference/rest/v2/Job
            # for alternative values for the writeDisposition
            # or consider using partitioned tables
            # https://cloud.google.com/bigquery/docs/partitioned-tables
            bq_join_holidays_weather_data = BigQueryInsertJobOperator(
                task_id=f"bq_join_holidays_weather_data_{str(year)}",
                configuration={
                    "query": {
                        "query": WEATHER_HOLIDAYS_JOIN_QUERY,
                        "useLegacySql": False,
                        "destinationTable": {
                            "projectId": PROJECT_NAME,
                            "datasetId": BQ_DESTINATION_DATASET_NAME,
                            "tableId": BQ_DESTINATION_TABLE_NAME,
                        },
                        "writeDisposition": "WRITE_APPEND",
                    }
                },
                location="US",
            )

        s3_to_gcs_op >> load_external_dataset >> bq_join_group >> create_batch

Use the Airflow UI to add variables

In Airflow, variables are an universal way to store and retrieve arbitrary settings or configurations as a simple key value store. This DAG uses Airflow variables to store common values. To add them to your environment:

  • Access the Airflow UI from the Cloud Composer console
  • Go to Admin > Variables
  • Add the following variables:
    • s3_bucket - the name of the s3 bucket you created earlier
    • gcp_project - your project ID
    • gcs_bucket - the name of the bucket you created earlier without the "gs://" prefix.
    • gce_region - the region where you want your Dataproc job that meets Dataproc Serverless networking requirements. This is the region where you enabled private Google access earlier.
    • dataproc_service_account - the service account for your Cloud Composer environment. You can find this service account on the environment configuration tab for your Cloud Composer environment.

Upload the DAG to your environment's bucket

Cloud Composer schedules DAGs that are located in the /dags folder in your environment's bucket. To upload the DAG using the Google Cloud console:

  1. On your local machine, save s3togcsoperator_tutorial.py
  2. In Google Cloud console, go to the Environments page.

    Go to Environments

  3. In the list of environments, In the DAG folder column click the DAGs link. The DAGs folder of your environment opens.

  4. Click Upload files

  5. Select s3togcsoperator_tutorial.py on your local machine and click Open

Trigger the DAG

  1. In your Cloud Composer environment, click the DAGs tab
  2. Click into DAG id s3_to_gcs_dag
  3. Click Trigger DAG
  4. Wait about five to ten minutes until you see a green check indicating the tasks have been completed successfully.

Validate the DAG's success

  1. In Google Cloud console, go to the BigQuery page.

    Go to BigQuery

  2. In the Explorer panel, click your project name.

  3. Click holidays_weather_joined.

  4. Click preview to view the resulting table. Note that the numbers in the value column are in tenths of a degree celsius.

  5. Click holidays_weather_normalized.

  6. Click preview to view the resulting table. Note that the numbers in the value column are in degree celsius.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this tutorial, either delete the project that contains the resources, or keep the project and delete the individual resources.

Delete the project

    Delete a Cloud project:

    gcloud projects delete PROJECT_ID

Delete individual resources

  1. Delete the holidays.csv file in your AWS S3 bucket
  2. Delete the AWS S3 bucket that you created
  3. In the Google Cloud console, go to the Cloud Storage Browser page.

    Go to Browser

  4. Click the checkbox for the bucket that you want to delete.
  5. To delete the bucket, click Delete, and then follow the instructions.
  6. Delete the BigQuery dataset
  7. Delete the Cloud Composer environment

What's next