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Get covid testing data from NY Health API and persist in Postgres

📝 Table of Contents

🧐 About

Two dags named NY_COVID_INITIAL_LD and LOAD_NY_COVID_DLY will help us get historical and ongoing daily loads from New York Covid testing data.

🧐 Objective

The objective here is to get NY Covid testing data for all counties and persist the data in a database. Each county to have its own table. The task should execute at a specific time everyday and populate the tables.

🏁 Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Clone this repo to your machine and follow the instructions under Usage

🎈 Usage

A step by step series of examples that tell you how to get a development env running.

  • Clone the Repo
git clone
  • Start docker build
docker-compose -f docker-compose.yaml up airflow-init
docker-compose -f docker-compose.yaml up
  • Keep checking docker processes to make sure all machines are helthy
docker ps
  • Once you notice that all containers are healthy. Access Airflow UI
http://localhost:8080

  • Edit the postgres_default connection from the UI or through command line if you want to persist data in postgres as part of the dags you create. Even better you can always add a new connection.

      Update: Ignore this step as this has now been accommodated in the new docker compose yaml

  ./airflow.sh bash 

  airflow connections add 'postgres_new' --conn-uri 'postgres://airflow:airflow@postgres:5432/airflow'

  connect to postgres and create new database with name 'userdata'

🎈 Airflow DAG Details

  • Activate the DAG NY_COVID_INITIAL_LD. What does it do?

    • Created tables for all 62 counties in New York in Postgres under database userdata.
    • Creates function and trigger in postgres to auto-populate the all the 62 counties with their data.
    • Makes a call to NY Health API and gets data in json.
    • Loads this json data to Postgres table.

  • The next day activate the Dag : LOAD_NY_COVID_DLY. What does it do?

    • Gets execution date from Airflow context
    • Calls the NY Helath API with that date and saves result in json.
    • Loads this data to Postgres table.

Airflow and other Concepts Used

  • TaskGroups
    • To create all the county tables
  • Task Flow Api
    • Using Task Flow with classic operators.
    • Adding task retires with Task Flow style dag definition
  • Airflow Macros
    • To get the execution date in the Daily DAG.
    • Used in conjunction with TaskFlow API.
  • Postgres psql function
    • To populate child tables when master table is populated.
  • Airflow Unit Tests
  • Create multiple databases in postgres as part of docker compose.

Airflow UnitTests

Unit test for airflow dags has been defined and present in the test folder. This folder is also mapped to the docker containers inside the docker-compose.yaml file. Follow below steps to execute unittests after the docker containers are running:

./airflow bash

python -m unittest discover -v

image

✍️ ToDo

  • The Objective can be achieved by just one daily dag and using backfill and catchup.
  • Explore the new rest Api of Airflow
    • Maybe implement rest api test framework using RestAssured :)
  • Implement Audit jobs or explore greatexpectations operator.
  • Implement Unit testing for the Dags and operators.

✍️ Authors