I have react & FastAPI being served with nginx using docker. When I run docker-compose up, everything works with the react app available at localhost:3000 and api available at localhost:8000. For instance, the get request localhost:8000/fleets/ returns the desired result. I would like the api to be reached at localhost:3000/api/ instead though.

When I add --root-path /api to the FastAPI Dockerfile, the react app still loads at localhost:3000 and I am able to reach the api at localhost:3000/api/, but my react app gets 404 errors when it tries to query for the api. When I go to the Network on tab in Chrome I see react queries for http://127.0.0.1:8000/api/fleets/ leading to a 404 error. The api still available at localhoost:8000/fleets/ though.

Should my react app be querying at localhost:3000/api/ or localhost:8000 and how do I make this adjustment?

Note I am using axios but changing axios.defaults.baseURL doesn't appear to make an impact. I currently have axios.defaults.baseURL = '/'; in my react App.jsx.

I have also removed "proxy": "http://127.0.0.1:3000" from my react package.json. In FastAPI, I have origins = ["http://localhost:3000", "http://127.0.0.1:8000"] for dealing with CORS.

FastAPI Dockerfile:

FROM python:3.8-alpine
ENV PYTHONBUFFERED 1
WORKDIR /api
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY . .

react Dockerfile:

FROM node:15.13-alpine
WORKDIR /react
COPY . .
RUN yarn run build

nginx-setup.conf:

upstream api {
    server backend:8000;
}

server {
    listen 8080;

    location / {
        root /var/www/react;
    }

    location /api/ {
        proxy_pass http://api/;
        proxy_set_header Host $http_host;
    }
}

docker-compose.yml:

version: '3'

services:
  backend:
    build:
      context: ./api
    command: uvicorn app.main:app --host 0.0.0.0 --port 8000 --root-path /api
    ports:
      - 8000:8000
  
  frontend:
    build:
      context: ./react
    volumes:
      - react_build:/react/build

  nginx:
    image: nginx:latest
    ports:
      - 3000:8080
    volumes:
      - ./nginx/nginx-setup.conf:/etc/nginx/conf.d/default.conf:ro
      - react_build:/var/www/react
    depends_on:
      - backend
      - frontend

volumes:
  react_build:

EDIT (for more details)

When running without the --root-path /api:

• localhost:3000/api/fleets/ does actually work.
• localhost:3000/api/fleets gets redirected to localhost:3000/fleets/ which gives nginx 404
• localhost:3000/api/docs gives Failed to load API definition error.
• localhost:8000/docs works.
• localhost:8000/fleets/ works.
• localhost:8000/fleets gets redirected to localhost:8000/fleets/ and works.
• React app pings http://127.0.0.1:8000/fleets and gets redirected to http://127.0.0.1:8000/fleets/ which works.

When running with --root-path /api:

• localhost:3000/api/fleets/ works
• localhost:3000/api/fleets gets redirected to localhost:3000/api/fleets/ and works
• localhost:3000/api/docs works
• localhost:8000/docs gives Failed to Load API definition error.
• http://localhost:8000/fleets/ works.
• http://localhost:8000/fleets gets redirected to localhost:8000/api/fleets/ and gives FastAPI404{"detail": "Not Found"}`

EDIT Here's a bare-bones reproducible example:

.
├── backend
│   ├── app
│   │   └── main.py
│   ├── Dockerfile
│   └── requirements.txt
├── docker-compose.yml
├── frontend
│   ├── Dockerfile
│   ├── package.json
│   ├── src
│   │   ├── App.css
│   │   ├── App.jsx
│   │   ├── App.test.js
│   │   ├── index.css
│   │   ├── index.js
│   │   ├── logo.svg
│   │   ├── reportWebVitals.js
│   │   └── setupTests.js
│   └── yarn.lock
├── nginx
    └── nginx-setup.conf

./backend/app/main.py

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

app = FastAPI()

origins = [
    "http://localhost:3000"
]

app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

@app.get("/day", tags=["Dates"])
async def get_day_of_week(day_num: int = 0):
    """
    Get the current day of week
    """
    days = ['Sun', 'Mon', 'Tues', 'Wed', 'Thur', 'Fri', 'Sat']
    return days[day_num]

./backend/Dockerfile

FROM python:3.8-alpine
ENV PYTHONBUFFERED 1
WORKDIR /alpine
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
COPY . .

./backend/requirements.txt

anyio==3.6.1
click==8.1.3
colorama==0.4.5
fastapi==0.78.0
h11==0.13.0
idna==3.3
pydantic==1.9.1
sniffio==1.2.0
starlette==0.19.1
typing_extensions==4.3.0
uvicorn==0.18.2

./frontend/src/App.jsx

import React, { useState, useEffect } from 'react';
import './App.css';

function App() {

  const [error, setError] = useState(null); 
  const [day, setDay] = useState('Sun');

  useEffect(() => {
    fetch('http://localhost:3000/api/day?day_num=3')
    .then((res) => setDay(res.data))
    .catch((err) => setError(err.message))
  }, []);

  return (
    <>
    <>Hello</>
    <>{day}{error}</>
    </>
  );
}

export default App;

./frontend/Dockerfile

FROM node:15.13-alpine
WORKDIR /frontend
COPY . .
RUN yarn run build

./frontend/.dockerignore

#node_modules
build

./frontend/package.json

{
    "name": "frontend",
    "version": "0.1.0",
    "private": true,
    "dependencies": {
      "@testing-library/jest-dom": "^5.14.1",
      "@testing-library/react": "^11.2.7",
      "@testing-library/user-event": "^12.8.3",
      "axios": "^0.27.2",
      "react": "^17.0.2",
      "react-dom": "^17.0.2",
      "react-scripts": "4.0.3",
      "web-vitals": "^1.1.2"
    },
    "scripts": {
      "start": "react-scripts start",
      "build": "react-scripts build",
      "test": "react-scripts test",
      "eject": "react-scripts eject"
    },
    "eslintConfig": {
      "extends": [
        "react-app",
        "react-app/jest"
      ]
    },
    "browserslist": {
      "production": [
        ">0.2%",
        "not dead",
        "not op_mini all"
      ],
      "development": [
        "last 1 chrome version",
        "last 1 firefox version",
        "last 1 safari version"
      ]
    }
  }

./nginx/nginx-setup.conf

upstream api {
    server backend:8000;
}

server {
    listen 8080;

    location / {
        root /var/www/react;
    }

    location /api/ {
        proxy_pass http://api/;
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

./docker-compose.yml

version: '3'

services:
  backend:
    build:
      context: ./backend
    command: uvicorn app.main:app --host 0.0.0.0 --port 8000 --root-path /api
    ports:
      - 8000:8000

  frontend:
    build:
      context: ./frontend
    volumes:
      - react_build:/frontend/build

  nginx:
    image: nginx:latest
    ports:
     - 3000:8080
    volumes:
      - ./nginx/nginx-setup.conf:/etc/nginx/conf.d/default.conf:ro
      - react_build:/var/www/react
    depends_on:
      - backend
      - frontend
volumes:
  react_build: