Check if python script is running on an aws instance

Question

I'm trying to set up a python logger to send error emails when it logs an error iff the instance has a tag set. I then quickly run into the problem of local dev computers that aren't on aws. Is there an easy and fast way to check if the script is being run on aws?

I was loading the instance data with:

import boto.utils
from boto.ec2.connection import EC2Connection
metadata = boto.utils.get_instance_metadata()
conn = EC2Connection()
instance = conn.get_only_instances(instance_ids=metadata['instance-id'])[0]

I can of course use a timeout on get_instance_metadata, but there is then a tension between now long to make developers wait vs the possibility of not sending an error email in production.

Can anyone think of a nice solution?

Answer 1

Similar to @cgseller, assuming python3, one could do something like:

from urllib.request import urlopen

def is_ec2_instance():
    """Check if an instance is running on AWS."""
    result = False
    meta = 'http://169.254.169.254/latest/meta-data/public-ipv4'
    try:
        result = urlopen(meta).status == 200
    except ConnectionError:
        return result
    return result

Answer 2

Alternatively, you can check if your environment contains any AWS environmental variables:

is_aws = True if os.environ.get("AWS_DEFAULT_REGION") else False

I chose to inspect if my user name is an ec2 instance: (Not a great solution, but it works)

my_user = os.environ.get("USER")
is_aws = True if "ec2" in my_user else False