Connect Airflow, Presto, and Cassandra

Learn how to connect Airflow, Presto, and Cassandra all on your browser via Gitpod! This demo can also be done on your local via Docker.

Click below to get started!

1. Start Presto and Cassandra Docker Containers and install Airflow

IMPORTANT: Remember to make the ports public when the dialog shows in the bottom righthand corner!

1.1 Run setup script

bash setup.sh

2. Open a new terminal and confirm services are running

2.1 Confirm Docker containers are running

docker ps

2.2 Airflow UI on port 7080 and log in

username: admin
password: password

2.3 Presto UI on port 8080

3. Setup Presto Connection in Airflow Admin

3.1 Get IP Address

hostname -I | awk '{print $2}'

3.2 Fill in presto_default connection with the following items and then confirm by testing the connection

Connection Type: Presto
Host: value copied from 3.1
Schema: remove hive and leave blank
Login: admin
Port: 8080

4. Create Cassandra Catalog in Presto

4.1 Update {hostname} in cassandra.properties file with value from 3.1

sed -i "s/{hostname}/$(hostname -I | awk '{print $2}')/" cassandra.properties

4.2 Copy cassandra.properties to Presto container

docker cp cassandra.properties $(docker container ls | grep 'presto' | awk '{print $1}'):/opt/presto-server/etc/catalog/cassandra.properties

4.3 Confirm cassandra.properties was moved to Presto container

docker exec -it presto sh -c "ls /opt/presto-server/etc/catalog"

5. Confirm Presto CLI can see Cassandra catalog

5.1 Start Presto CLI

docker exec -it presto presto-cli

5.2 Run show command

show catalogs ;

If you do not see cassandra, then we need to restart the container

5.3 Restart Presto container

docker restart presto

5.4 Repeat 5.1 and 5.2 and confirm if you can now see the cassandra catalog

6. Set up Cassandra data

6.1 Copy CQL file onto Cassandra Container

docker cp setup.cql $(docker container ls | grep 'cassandra' | awk '{print $1}'):/

6.2 Run CQL file

docker exec -it cassandra cqlsh -f setup.cql

7. Run DAGs

7.1 Move DAGs into Dags Folder

mkdir ~/airflow/dags && mv presto_read_from_cassandra.py ~/airflow/dags && mv presto_join_and_xcom.py ~/airflow/dags && mv presto_write_to_cassandra.py ~/airflow/dags

7.2 While waiting on scheduler to pick up Dags, create Presto query variable

7.2.1 Under Airflow Admin in the UI, click variables

7.2.2 Click the blue plus sign to create a variable

7.2.3 Fill in the key and values as below:

key: presto_query
value: select * from cassandra.demo.spacecraft_journey_catalog;

7.3 Confirm scheduler has picked up the DAGs in Airflow UI (might take a couple minutes)

7.4 Enable and Run Read From Cassandra Dag

7.4.1 Click on the logs to visualize the result of the Presto query

7.5 Update the presto_query value to the below in Airflow variables

select cassandra.demo.spacecraft_journey_catalog.spacecraft_name, cassandra.demo.spacecraft_journey_catalog.summary, cassandra.demo.spacecraft_speed_over_time.speed from cassandra.demo.spacecraft_journey_catalog inner join cassandra.demo.spacecraft_speed_over_time on cassandra.demo.spacecraft_journey_catalog.journey_id = cassandra.demo.spacecraft_speed_over_time.journey_id;

7.6 Enable and run Join and XCOM Dag

7.6.1 Click on the logs to visualize the result of the Presto query and see how they change from the first task to the second task

7.7 Enable and run Write to Cassandra Dag

7.7.1 Once completed, check out the logs on the write_to_cassandra task

7.7.2 Confirm writes went through to Cassandra

docker exec -it cassandra cqlsh -e "select * from demo.spacecraft_journey_summary_and_speed"