How to dynamically add EC2 ip addresses to Django ALLOWED_HOSTS

Question

We\'ve recently changed our deployment strategy to use AWS auto scaling group.

One problem we have in production is with the newly created EC2s.
Our Application sta

Answer 1

You can retrieve an EC2 instance Meta data by making an API request to

curl http://169.254.169.254/latest/meta-data/
GET http://169.254.169.254/latest/meta-data/

source

And you can get just the private IP for a specific instance by making an API call:

GET http://169.254.169.254/latest/meta-data/local-ipv4

So in your Django settings file add this script to "dynamically" add IPs to your allowed hosts:

import requests
EC2_PRIVATE_IP = None
try:
    EC2_PRIVATE_IP = requests.get(
        'http://169.254.169.254/latest/meta-data/local-ipv4',
        timeout=0.01).text
except requests.exceptions.RequestException:
    pass

if EC2_PRIVATE_IP:
    ALLOWED_HOSTS.append(EC2_PRIVATE_IP)

Answer 2

The snippets below will find either the Public IP address or the Elastic IP address associated with your EC2 instance and append it to ALLOWED_HOSTS.

• Install PyCurl

  pip install pycurl
  

• Python 3

  import pycurl
  from io import BytesIO
  
  # Determine Public IP address of EC2 instance
  buffer = BytesIO()
  c = pycurl.Curl()
  c.setopt(c.URL, 'checkip.amazonaws.com')
  c.setopt(c.WRITEDATA, buffer)
  c.perform()
  c.close()
  # Body is a byte string, encoded. Decode it first.
  ALLOWED_HOSTS.append(buffer.getvalue().decode('iso-8859-1').strip())
  

• Python 2

  import pycurl
  from StringIO import StringIO
  
  buffer = StringIO()
  c = pycurl.Curl()
  c.setopt(c.URL, 'checkip.amazonaws.com')
  c.setopt(c.WRITEDATA, buffer)
  c.perform()
  c.close()
  # In Python 2, we can cast the return value to
  # string without knowing the exact encoding.
  ALLOWED_HOSTS.append(str(buffer.getvalue()).strip())