Ansible EC2 Hosts Script Missing Instance

Question

For some reason, ansible's ec2 hosts is missing instances. ec2-describe-instances returns the correct instances, but /etc/ansible/hosts does not:

[root@or-manage ec2-user]# ec2-describe-instances | grep seed
TAG     instance        i-ff0b2f36      Name    cass-uat-seed
[root@or-manage ec2-user]# /etc/ansible/hosts | grep seed
[root@or-manage ec2-user]#

You can see that ec2-describe-instances has the instance with the tag I'm looking for, but ansible hosts does not.

Why is that instance not in there for /etc/ansible/hosts?

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Note: At first, I thought it was /etc/ansible/hosts using the wrong region, but I turned up the boto debug and it IS the correct region:

send: 'POST / HTTP/1.1\r\nAccept-Encoding: identity\r\nContent-Length: 221\r\nContent-Type: application/x-www-form-urlencoded; charset=UTF-8\r\nHost: ec2.us-west-2.amazonaws.com

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Update 1:

I've noticed that any instances without a public IP do not appear in the /etc/ansible/hosts list. Why would that be?

Answer 1

I had to tweak the following knobs (in /etc/ansible/ec2.ini):

# This is the normal destination variable to use. If you are running Ansible
# from outside EC2, then 'public_dns_name' makes the most sense. If you are
# running Ansible from within EC2, then perhaps you want to use the internal
# address, and should set this to 'private_dns_name'. The key of an EC2 tag
# may optionally be used; however the boto instance variables hold precedence
# in the event of a collision.
destination_variable = private_dns_name

# For server inside a VPC, using DNS names may not make sense. When an instance
# has 'subnet_id' set, this variable is used. If the subnet is public, setting
# this to 'ip_address' will return the public IP address. For instances in a
# private subnet, this should be set to 'private_ip_address', and Ansible must
# be run from within EC2. The key of an EC2 tag may optionally be used; however
# the boto instance variables hold precedence in the event of a collision.
vpc_destination_variable = private_ip_address