/cqrsPythonExercises

Primary LanguagePython

serverlessCqrsPython

Welcome to the exercises for CQRS in Python.

An important caveat for Python.

JSON in Python is case sensitive. By convention, I have named all class variables in python in camel case starting with an upper case letter. For example, the hotel identifier is HotelId, the reservation identifier is ReservationId. The JSON text you send to the API **must** match the case of the class variables or serialization will fail.

Once you have checked out the code, you will need the following set up on your workstation:

  1. A local installation of EventStoreDB from https://www.eventstore.com/ is required to run this project. Make sure that the event store database is installed and running. This can be verified by loading http://localhost:2113/web/index.html#/ The default username/password is admin/changeit. Commands cannot be issued to the hotel reservation system without an active event store. There are 2 methods of installing event store.

    1. A docker-compose.yml file has also been provided in the repositories root directory. Execute the command docker-compose up in the root directory if you have docker installed.
    2. You can find installation instructions for Event Store Db at https://www.eventstore.com/.

  2. Python 3, I suggest python 3.7, available from https://realpython.com/installing-python/#how-to-install-python-on-linux for Linux or the windows store https://www.microsoft.com/en-ca/p/python-37/9nj46sx7x90p for Windows.

  3. pip, the python package installer. Type pip help at a command line to see if it's already installed after installing python. pip can be installed using the instructions at https://phoenixnap.com/kb/install-pip-windows for Windows or https://pip.pypa.io/en/stable/installing/ for Linux

  4. An IDE, I've used both pycharm and Visual Studio Code to develop this repository.

    1. Azure Functions - you can run the examples as an Azure Function, but you must install the Azure functions core tools. If you choose Azure functions, you will have to run and debug using Visual Studio Code. Instructions for debugging and running Azure Functions can be found at https://docs.microsoft.com/en-us/azure/developer/python/tutorial-vs-code-serverless-python-04
    2. pycharm from jet brains can also be used, as the code can be run as a flask app

  5. Install dependencies, if you use pycharm or Visual Studio Code, the IDE will install all required python libraries. The IDE will not install Azure functions core tools, you must do this step yourself.

  6. You can install the dependencies from the command line. In the exercises serverlessCqrsPython directory, using the provided requirements.txt file and pip by entering the command pip install -r requirements.txt

Running the code through the IDE is the easiest way to get started. pycharm should modify all path's so that the libraries developed for this module are found. The Azure functions module appends to the system path to ensure that all python classes can be found. If you're a purist and want to run everything from the command line, you will have to modify your PYTHONPATH environment variable to include the root directory of the excercise you are currently working on.

Running the Flask project in pycharm

Once you have loaded the serverlessCqrsPython directory as a project in pycharm, you will be required to choose a python interpreter in the IDE settings. The entry point for the Hotel Management API is a directory called serverlessCqrsPython. For example, for the inital exercises, have pycharm open the directory of `exercise 1 - 4 start/serverlessCqrsPython`. To run the flask project in pycharm, you can run the file in `serverlessCqrsPython/FlaskProject/app.py`. Here you will find the entry point for the MakeReservation command which is in a function called make_reservation. Debug or run app.py within the IDE to start the hotel reservation system under as a Flask web app. The web app will run at http://localhost:5000

Running the Azure Function project in Visual Studio Code

If you prefer to run the hotel reservation system as an Azure function you must do so using Visual Studio Code unless you are very familiar with the Azure functions command line interface. Your entry point for Azure functions is a file called `__init__.py` in a directory called MakeReservation. Azure functions written in python are named after the directory that contains them. The azure functions will be hosted locally at http://localhost:7071/api .