How can the application find this information?
Query the instance metadata from http://169.254.169.254/latest/meta-data/.
Query the instance user data from http://169.254.169.254/latest/user-data/.
Query the Amazon Machine Image (AMI) information from http://169.254.169.254/latest/meta-data/ami/.
Check the hosts file of the operating system.
Explanations:
Querying the instance metadata fromhttp://169.254.169.254/latest/meta-data/provides the public IPv4 address of the instance under thepublic-ipv4field.
User data, accessible athttp://169.254.169.254/latest/user-data/, contains configuration data passed to the instance at launch, not the public IPv4 address.
The AMI information, accessed fromhttp://169.254.169.254/latest/meta-data/ami/, provides details about the Amazon Machine Image but does not include the public IPv4 address.
The hosts file of the operating system may not contain the public IPv4 address, as it typically maps hostnames to IP addresses but does not dynamically update with the instance’s public IP.
From my perspective, the answer is:
Query the instance metadata from http://169.254.169.254/latest/meta-data/.