CORS issue when React.js app sends request to Django backend

Question

I have Django app (XXX.XXX.XXX.XXX:55002) and React.js front-end (XXX.XXX.XXX.XXX:55001). The app works perfectly locally, but I have CORS issue in the server. I can properly open the front-end in the server, but when it sends the request to Django app via HTTP, then it throws error:

Invalid HTTP_HOST header: 'XXX.XXX.XXX.XXX:55002'. You may need to add 'XXX.XXX.XXX.XXX' to ALLOWED_HOSTS.

OPTIONS http://XXX.XXX.XXX.XXX:55002/predict?&arrivalDelay=5&schedTurnd=45 400 (Bad Request) fetchData @ Test.js:89 value @ Test.js:40 Ia @ react-dom.production.min.js:5351 Ra @ react-dom.production.min.js:5099 Aa @ react-dom.production.min.js:5066 za @ react-dom.production.min.js:5481 En @ react-dom.production.min.js:1731 (index):1 Access to fetch at 'http://XXX.XXX.XXX.XXX:55002/predict?&arrivalDelay=5&schedTurnd=45' from origin 'http://XXX.XXX.XXX.XXX:55001' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

This is the code of settings.py. As you can see I added XXX.XXX.XXX.XXX to ALLOWED_HOSTS:

import os

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/2.1/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'hfkahsf'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = ['XXX.XXX.XXX.XXX', 'localhost', '127.0.0.1']

# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'crida_backend.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'crida_backend.wsgi.application'


# Database
# https://docs.djangoproject.com/en/2.1/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Password validation
# https://docs.djangoproject.com/en/2.1/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]

# Internationalization
# https://docs.djangoproject.com/en/2.1/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/2.1/howto/static-files/

STATIC_URL = '/static/'

This is the fetch part of Test.js:

  fetch(url, {
    method: "GET",
    dataType: "JSON",
    headers: {
      "Content-Type": "application/json; charset=utf-8",
    }
  })
  .then((resp) => {
    return resp.json()
  })
  .then((data) => {
    this.updateDelay(data.prediction,data.probability)
  })
  .catch((error) => {
    console.log(error, "catch the hoop")
  })

Answer 1

Follow these Steps to use django-cors-headers:

1. pip install django-cors-headers

2. Then add it to your installed apps which is in your settings.py:

   INSTALLED_APPS = (
       ...
       'corsheaders',
        ...
   )
   

3. Add CORS_ORIGIN_WHITELIST to your settings.py

   CORS_ORIGIN_WHITELIST = (
       '10.10.30.37:3000'      # <-- update
   )
   

Or

3. Add CORS_ORIGIN_ALLOW_ALL and set it to True so that it will accept request from any domain.

   CORS_ORIGIN_ALLOW_ALL = True
   

4. Add Middleware in your settings.py:

   MIDDLEWARE = [  # Or MIDDLEWARE_CLASSES on Django < 1.10
    ...
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.common.CommonMiddleware',
    ...
   ]