How do I get the public dns of an instance in AWS

Question

I get the elb details of a specific region, say Europe. Then I am able to get the instances that are related to the ELB. The problem is I am not able to get the public dns of those instances. What I do is:

conn = regions[3].connect(aws_access_key_id= access, aws_secret_access_key = secret_key)
loadbalancers = conn.get_all_load_balancers()
for lb in loadbalancers:
    print lb.instances

How to get the public_dns_name of these instances?

When I try:

for i in lb.instances:
    i.public_dns_name

AttributeError: 'InstanceInfo' object has no attribute 'public_dns_name'

Answer 1

The "instances" attribute of the LoadBalancer class only contains a tiny bit of information about the instance - it's not a full Instance object. To get the full instance object you must use the instanceId, which is available, to query for more info. This code snippet extends yours with the required calls:

#Create connection to ec2, credentials stored in environment
ec2_conn = connect_ec2()

conn = regions[3].connect(aws_access_key_id= access, aws_secret_access_key = secret_key)
loadbalancers = conn.get_all_load_balancers()
for lb in loadbalancers:
    for i in lb.instances:
        #Here, 'i' is an InstanceInfo object, not a full Instance
        instance_id = i.id

        #Query based on the instance_id we've got
        #This function actually gives reservations, not instances
        reservations = ec2_conn.get_all_instances(instance_ids=[instance_id])
        #pull out our single instance
        instance = reservations[0].instances[0]

        #Now we've got the full instance and we can get parameters from here
        print(instance.public_dns_name)