So I’m studying for my Amazon Web Services Associate Architect ticket at the moment and, in the coursework I’m doing, I came across this really neat feature in AWS.

If you’re on an  EC2 instance (a VM), and you do..

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

You get a whole load of metadata back, like this..

ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
events/
hostname
iam/
identity-credentials/
instance-action
instance-id
instance-life-cycle
instance-type
ipv6
local-hostname
local-ipv4
mac
managed-ssh-keys/
metrics/
network/
placement/
profile
public-hostname
public-ipv4
reservation-id
security-groups
services/

All you need to do now is pick any of these sub-topics and query it again…

curl http://169.254.169.254/latest/meta-data/local-hostname

and you get

ip-10-16-57-144.ec2.internal

or query

curl http://169.254.169.254/latest/meta-data/instance-type

ans you get

t2.micro

Nice huh?  As the feature is a URL, then you can be sure you can query it from a Flask or NodeJS app directly so an app can now be aware of what kind of hardware it’s running on, so you could even have an app that would report in telemetry to a central server to let developers know about the characteristics of the host in relation to the app performance.  Quite a neat piece of internal architecture.

Nice.