Source code for airflow.providers.amazon.aws.example_dags.example_hive_to_dynamodb

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"""
   This DAG will not work unless you create an Amazon EMR cluster running
   Apache Hive and copy data into it following steps 1-4 (inclusive) here:
   https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/EMRforDynamoDB.Tutorial.html
"""

import os
from datetime import datetime

from airflow import DAG
from airflow.decorators import task
from airflow.models import Connection
from airflow.providers.amazon.aws.hooks.dynamodb import DynamoDBHook
from airflow.providers.amazon.aws.transfers.hive_to_dynamodb import HiveToDynamoDBOperator
from airflow.utils import db

[docs]DYNAMODB_TABLE_NAME = 'example_hive_to_dynamodb_table'
[docs]HIVE_CONNECTION_ID = os.getenv('HIVE_CONNECTION_ID', 'hive_on_emr')
[docs]HIVE_HOSTNAME = os.getenv('HIVE_HOSTNAME', 'ec2-123-45-67-890.compute-1.amazonaws.com')

# These values assume you set up the Hive data source following the link above.
[docs]DYNAMODB_TABLE_HASH_KEY = 'feature_id'
[docs]HIVE_SQL = 'SELECT feature_id, feature_name, feature_class, state_alpha FROM hive_features'


@task
[docs]def create_dynamodb_table():
    client = DynamoDBHook(client_type='dynamodb').conn
    client.create_table(
        TableName=DYNAMODB_TABLE_NAME,
        KeySchema=[
            {'AttributeName': DYNAMODB_TABLE_HASH_KEY, 'KeyType': 'HASH'},
        ],
        AttributeDefinitions=[
            {'AttributeName': DYNAMODB_TABLE_HASH_KEY, 'AttributeType': 'N'},
        ],
        ProvisionedThroughput={'ReadCapacityUnits': 20, 'WriteCapacityUnits': 20},
    )

    # DynamoDB table creation is nearly, but not quite, instantaneous.
    # Wait for the table to be active to avoid race conditions writing to it.
    waiter = client.get_waiter('table_exists')
    waiter.wait(TableName=DYNAMODB_TABLE_NAME, WaiterConfig={'Delay': 1})


@task
[docs]def get_dynamodb_item_count():
    """
    A DynamoDB table has an ItemCount value, but it is only updated every six hours.
    To verify this DAG worked, we will scan the table and count the items manually.
    """
    table = DynamoDBHook(resource_type='dynamodb').conn.Table(DYNAMODB_TABLE_NAME)

    response = table.scan(Select='COUNT')
    item_count = response['Count']

    while 'LastEvaluatedKey' in response:
        response = table.scan(Select='COUNT', ExclusiveStartKey=response['LastEvaluatedKey'])
        item_count += response['Count']

    print(f'DynamoDB table contains {item_count} items.')


# Included for sample purposes only; in production you wouldn't delete
# the table you just backed your data up to.  Using 'all_done' so even
# if an intermediate step fails, the DAG will clean up after itself.
@task(trigger_rule='all_done')
[docs]def delete_dynamodb_table():
    DynamoDBHook(client_type='dynamodb').conn.delete_table(TableName=DYNAMODB_TABLE_NAME)


# Included for sample purposes only; in production this should
# be configured in the environment and not be part of the DAG.
# Note: The 'hiveserver2_default' connection will not work if Hive
# is hosted on EMR.  You must set the host name of the connection
# to match your EMR cluster's hostname.
@task
[docs]def configure_hive_connection():
    db.merge_conn(
        Connection(
            conn_id=HIVE_CONNECTION_ID,
            conn_type='hiveserver2',
            host=HIVE_HOSTNAME,
            port=10000,
        )
    )


with DAG(
    dag_id='example_hive_to_dynamodb',
    schedule_interval=None,
    start_date=datetime(2021, 1, 1),
    tags=['example'],
    catchup=False,
) as dag:
    # Add the prerequisites docstring to the DAG in the UI.
[docs]    dag.doc_md = __doc__

    # [START howto_transfer_hive_to_dynamodb]
    backup_to_dynamodb = HiveToDynamoDBOperator(
        task_id='backup_to_dynamodb',
        hiveserver2_conn_id=HIVE_CONNECTION_ID,
        sql=HIVE_SQL,
        table_name=DYNAMODB_TABLE_NAME,
        table_keys=[DYNAMODB_TABLE_HASH_KEY],
    )
    # [END howto_transfer_hive_to_dynamodb]

    (
        configure_hive_connection()
        >> create_dynamodb_table()
        >> backup_to_dynamodb
        >> get_dynamodb_item_count()
        >> delete_dynamodb_table()
    )