Complete guide to building Microservices using FastAPI

Microservices have become increasingly popular in recent years as a way to build scalable and flexible applications. In this tutorial, we will show you how to build microservices using FastAPI, a modern web framework for building APIs with Python.

FastAPI is a high-performance web framework for building APIs with Python 3.6+ based on standard Python type hints. It is easy to use, fast, and efficient, making it a great choice for building microservices.

Before we start building our microservices with FastAPI, make sure you have Python installed on your machine. You can download and install Python from the official website. Once you have Python installed, you can install FastAPI using pip:

pip install fastapi

You will also need an HTTP server to run our FastAPI application. We will be using Uvicorn, a lightning-fast ASGI server implementation, to run our FastAPI application. You can install Uvicorn using pip:

pip install uvicorn

Now that we have installed FastAPI and Uvicorn, let’s start building our microservices. Create a new Python file and import the necessary modules:

from fastapi import FastAPI

Next, create an instance of the FastAPI class:

app = FastAPI()

Now, let’s define a simple endpoint that returns a JSON response. We will create a route decorator that maps a URL path to a function that handles the request:

@app.get("/")
def read_root():
    return {"Hello": "World"}

To run our FastAPI application, we need to start the Uvicorn server and pass our FastAPI application instance as a parameter:

uvicorn app:app --reload

This command tells Uvicorn to run the app.py file, where our FastAPI application instance is defined, and to reload the server whenever the code changes.

Now, if you open a web browser and navigate to http://127.0.0.1:8000, you should see a JSON response with the message "Hello, World!"

Next, let’s create another endpoint that accepts parameters in the URL path. We can define path parameters by including curly braces in the URL path and specifying the parameter name:

@app.get("/{name}")
def read_item(name: str):
    return {"Hello": name}

In this example, we define a path parameter called "name" that accepts a string value. When you navigate to http://127.0.0.1:8000/John, you should see a JSON response with the message "Hello, John!"

Now that we have created a simple API with FastAPI, let’s expand our application to include multiple microservices. We can organize our application by creating separate Python files for each microservice. Each microservice will have its endpoints and business logic.

For example, let’s create a new Python file called userservice.py to handle user-related operations. In this file, we can define endpoints for creating, reading, updating, and deleting users:

from fastapi import APIRouter

router = APIRouter()

@router.post("/create_user")
def create_user(username: str):
    # create user logic here
    return {"message": f"User {username} created"}

@router.get("/get_user/{user_id}")
def get_user(user_id: int):
    # get user logic here
    return {"user_id": user_id, "name": "John Doe"}

@router.put("/update_user/{user_id}")
def update_user(user_id: int, new_username: str):
    # update user logic here
    return {"message": f"User {user_id} updated with new name {new_username}"}

@router.delete("/delete_user/{user_id}")
def delete_user(user_id: int):
    # delete user logic here
    return {"message": f"User {user_id} deleted"}

To include the userservice in our main FastAPI application, we need to import the userservice module and include the router in our FastAPI application instance:

from fastapi import FastAPI
from userservice import router as user_router

app = FastAPI()

app.include_router(user_router)

Now, when you run the Uvicorn server and navigate to http://127.0.0.1:8000/docs, you should see the Swagger UI documentation for our FastAPI application, including the endpoints defined in the userservice.py file.

In this tutorial, we have shown you how to build microservices with FastAPI, a modern web framework for building APIs with Python. FastAPI makes it easy to create flexible and scalable applications with built-in support for asynchronous programming and type checking.

By dividing our application into separate microservices, we can create a modular and maintainable architecture that allows us to scale and evolve our application over time. FastAPI’s support for dependency injection, request validation, and automatic documentation generation makes it a powerful tool for building microservices.

We hope this tutorial has been helpful in getting you started with building microservices with FastAPI. Happy coding!