Simple Service in Docker

Example of a simple service in Docker. It is using Redis and Flask. There are some ad hoc unit tests.

.
├── README.md
├── docker-compose.yml
├── Dockerfile
├── .healthcheck.sh
└── src
    ├── code
    │   ├── __init__.py
    │   ├── service.py
    │   └── service_test.py
    └── requirements.txt

Small Service deployed to a docker container that has two endpoints:

1. /messages

   • takes a message (a string) as a POST and returns the SHA256 hash digest of that message (in hexadecimal format)

2. /messages/<hash>

   • is a GET request that returns the original message. A request to a non-existent <hash> should return a 404 error.

1. Interoperability
   • Data format - Bad Request
   • Not availability - Server Error
2. Testability
   • Test Driven Development - Clear view of testing scenarios before and after the development
   • Integrate the tests with Docker
   • Creating a testing structure keeping it similar to the real interaction

1. POST request

   • curl -X POST -H "Content-Type: application/json; charset= utf-8" -d '{"message": "foo"}' http://0.0.0.0:8080/messages

   •  {
       "digest": "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"
      }
     

2. GET request

   • curl -i http://0.0.0.0:8080/messages/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae

   •  {
       "message": "foo"
      }
     

It is necessary to have installed Docker and Docker Compose. Follow the two links

1. https://docs.docker.com/install/#server to install Docker

2. https://docs.docker.com/compose/install/ to install Docker Compose

Move inside the main directory then run the following commands

1. docker-compose up --build
   • This creates/pull the images, start the container, run the unit tests, build and run
2. docker-compose down --rmi all
   • The opposite of before
3. docker-compose exec web sh
   • This opens the command line where the microservice is running. It is possible to change the code there.
4. docker-compose exec redis sh
   • This opens the command line where Redis is running
5. From outside of any container, it is possible to test the POST and GET request.

• The container is exposing the service on 8080 however the application is exposing the service on port 5000
• It is mounted a volume
• Docker run the unit tests before to build the images