OpenAPI 3 + Connexion + AioHTTP tutorial

The purpose of this tutorial is to facilitate learning about the OpenAPI 3 spec + Connexion + AioHTTP stack. And designing APIs according to the Google API Design Guide. Also use of proper linting and Python formatting is encouraged through a pre-commit hook. With some knowledge of how to use a shell (Mac/Linux/Unix - I prefer Bash) + Git + Python 3, you should be able to have this tutorial working for you pretty quickly. The interesting part of this tutorial is that there are Pytests for each step. This also works to demo test driven development. Each part of the tutorial has a different pytest file and a corresponding Makefile entry to make running it simple. Answers for each step in the tutorial are included in different Git branches named for the step.

Prerequisites

This tutorial assumes previous knowledge of the following:

• Python 3.7
• Python dependency management (pip, virtual environments, etc)
• Basic SQL syntax for PostgreSQL
• Restful API practices
• Google API Design Guide
• A shell like bash or zsh

Getting Started

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

Setup

Install Python 3.7 however you like. If you are using a Mac, Homebrew is an easy way to manage package installs. Pyenv is a great tool if you need to work with multiple versions of Python.

This project requires Docker. Setup by following their instructions.

Once the project is cloned to your computer, dependencies must be installed (preferably in a virtual environment). Install the necessary pip packages listed in the requirements.txt file.

If you receive an error while install the requirements about not finding the pg_config file you need to install a postgresql client before the psycopg2 install will work. If you are on a Mac with Homebrew, running brew install postgresql should fix the issue.

Running the AioHTTP server

If you can get the AioHTTP server running, then you know your environment is setup correctly for the rest of the tutorials.

Either you must run everything from the root of this project or add the project's directory to your PYTHONPATH.

To begin, start up your docker containers via:

make docker

After the PostgreSQL container starts it initializes some data. You can verify your PostgreSQL database is running using the command:

make psql

At the prompt you could then run the select query:

select * from kudos;

And you should receive a single row of data back. Use \q to exist the psql command line.

After docker container setup, you can run the app like:

make run

This will run your server in the foreground and monopolize the shell until you CTRL+C.

Then you can test the API by using curl in a new shell:

curl -v "http://127.0.0.1:9000/"

If you go to the URL in your browser, it will redirect you back to the Github project + README.

While the app is running, you can also view the local Swagger UI docs by opening your browser to localhost/ui.

Once you are finished exploring, you can safely CTRL+C to shut down the web server.

Running the tests

There are pytests which validate that you've correctly completed each step in this tutorial. You can run the tests by executing:

make tests

The first time you run this all the tests will fail. This is expected. You'll be doing the work in this tutorial to get the tests working.

Before committing code

Finally, if you want to contribute code back to the project. Please setup the provided githooks. You can do this with:

make githooks

Passing the tests

Each of the tests will require a few steps to get it working. First, you should modify index.yaml inside the spec folder. Each test will require adding new yaml under the paths directive. In addition, for test #2 you should add a new item under the components:schemas for the Kudo object which will be reused in tests #3 & #4.

Each time you modify the spec file, you'll need to run make spec to compile the new resolved.yaml.

Test 1 - Hello World

To get test 1 passing, you'll need to do a few items:

• Update index.yaml. You can look at the included / path as an example.
  1. Add a /hello-world route to the index.yaml
  2. Add a GET method to the route with a summary and description.
  3. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function. Don't worry too much about the Google API Design Guide on this one. It's just a 'Hello World'.
  4. Add a 200 response and description.
• Create your new handler file & function. You can look at handlers/root.py and AIOHTTP docs to figure this part out. You MUST return a JSON object with a single key of "Hello" and it's corresponding value set to "World". Hint don't forget the Content-Type header.
• After these changes, you can test your code. If you wish, you may use make run and hit your endpoint to see the results, or you can use the Makefile via make test_1.

Test 2 - Kudos Collection - GET method

To get test 2 passing, you'll need to do the following:

• Update index.yaml.
  1. Add a /kudos route to the index.yaml.

     The Kudo schema is already defined for you in the index.yaml file under schemas. To make the tests pass use this schema.

  2. Add a GET method to the route with a summary and description.
  3. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function.
  4. Add a 200 response and description. It should return a Kudo schema.
• Create your new handler file & function. Remember to follow the Google API Design Guide.

  You will run into an issue with Python's default json.dumps not being able to handle datetime objects natively. There are several clever workarounds, and it will be up to you to chose and implement one.

• It MUST read the existing kudo in the database using the db_conn setup in main.py. This is passed into the handler via the arg object which is an AioHTTP request class.

  This database connection uses the aiopg library.

• A kudo resource should contain all the attributes listed in the schema of index.yaml.
• After these changes, you can test your code. If you wish, you may use make run and hit your endpoint to see the results, or you can use the Makefile via make test_2.

Test 3 - Kudos Collection - POST method

To get test 3 passing, you'll need to do the following:

• Update index.yaml.
  1. Update the /kudos route in index.yaml and add a POST method. It should return the Kudo schema.
  2. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function.
  3. Add a 201 response and description. It should return a Kudo schema.
• Add your function to process the POST method. It should use the db_conn setup in main.py as in the previous step to save a new row to the database.
• The kudo resource returned should contain all the attributes listed in the schema of index.yaml.
• After these changes, you can test your code. If you wish, you may use make run and hit your endpoint to see the results, or you can use the Makefile via make test_3.

Test 4 - Kudo Resource - GET method

To get test 4 passing, you'll need to do the following:

• Update index.yaml.
  1. Add the /kudos/{id} route in index.yaml and add a GET method. It should return the Kudo schema.
  2. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function.
  3. Add a 200 response and description. It should return a Kudo schema.
• Add your function and test your code.

Test 5 - Kudo Resource - PUT method

To get test 5 passing, you'll need to do the following:

• Update index.yaml.
  1. Update the /kudos/{id} route in index.yaml and add a PUT method. It should take a kudo as input and return the Kudo schema.
  2. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function.
  3. Add a 200 response and description. It should return a Kudo schema.
• Add your function and test your code.

Make sure you update your updated_dt column with a new timestamp using SQL NOW() when the object is updated.

Test 6 - Kudo Resource - DELETE method

To get test 6 passing, you'll need to do the following:

• Update index.yaml.
  1. Update the /kudos/{id} route in index.yaml and add a DELETE method. It should return a 204 status and an empty body.
  2. Add a combination of x-openapi-router-controller (optional) and operationId (required) attributes pointing to your function.
  3. Add a 204 response and description.
• Add your function and test your code.