This case study demonstrates the process of Dockerizing a COBOL application for computing income taxes and integrating it into a Dockerized web stack, consisting of a React front end, a Python/Flask API, a COBOL shared library, a PostgreSQL database, and a Træfik reverse proxy.
Introduction
According to a 2015 report by Reuters1:
- 43% of banking systems are built on COBOL
- 80% of in-person transactions use COBOL
- 95% of ATM swipes rely on COBOL code
- 220 billion lines of COBOL are in use today
This application is a case study on Dockerizing a COBOL application for computing income taxes, and integrating it into a Dockerized web stack.
Prerequisites
Docker and docker-compose are needed to run the application. Installation instructions can be found at Install Docker and Install Docker Compose.
How It Works
This project is divided into several parts:
- Web Tier
- A React front end styled with Bootstrap running on Node
- API Tier
- A RESTful API built with Python and Flask
- A COBOL shared library for computing income taxes compiled with GnuCOBOL
- Responsible for retrieving taxpayer information from PostgreSQL and natively passing that information into a COBOL subroutine to compute income taxes owed
- Data Tier
- A PostgreSQL database containing taxpayer information
- Reverse Proxy
- Using Træfik as a reverse proxy and load balancer
- Docker Compose
- For orchestrating containers and pre-populating the database server
Running the App
Start the application with the following command:
sudo docker-compose up -d
To view the front end navigate to:
http://web.docker.localhost
The database is pre-populated with taxpayer IDs in the range of 1 - 1000. Enter a taxpayer ID and click Submit.
History
- 30th April, 2018: Initial release
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