In case a floating ip address is associated with a new instance via EC2 API call (AssociateAddress) and the address was already in use by another instance an exception is raised in the EC2 API and a error is returned to the caller of the API.
According to EC2 API Documentation this should not be the case and the address should be assigned to the new instance:
"""
For EC2 addresses: This action associates an Elastic IP address with an instance (not running in a VPC). If the IP address is currently assigned to another instance, the IP address is assigned to the new instance. For more information about EC2 Elastic IP addresses, go to Instance Addressing in the Amazon Elastic Compute Cloud User Guide.
"""
VERSION INFO:
Essex ubuntu package nova-api 2012.1-0ubuntu2
TRACES:
(nova.api.ec2): 2012-05-26 13:17:57,379 ERROR Unexpected error raised: Remote error: FloatingIpAssociated Floating ip 172.31.237.80 is associated.
[u'Traceback (most recent call last):\n', u' File "/usr/lib/python2.7/dist-packages/nova/rpc/amqp.py", line 252, in _process_data\n rval = node_func(context=ctxt, **node_args)\n', u' File "/usr/lib/python2.7/dist-packages/nova/network/manager.py", line 258, in wrapped\n return func(self, context, *args, **kwargs)\n', u' File "/usr/lib/python2.7/dist-packages/nova/network/manager.py", line 453, in associate_floating_ip\n raise exception.FloatingIpAssociated(address=floating_address)\n', u'FloatingIpAssociated: Floating ip 172.31.237.80 is associated.\n'].
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/nova/api/ec2/__init__.py", line 582, in __call__
result = api_request.invoke(context)
File "/usr/lib/python2.7/dist-packages/nova/api/ec2/apirequest.py", line 81, in invoke
result = method(context, **args)
File "/usr/lib/python2.7/dist-packages/nova/api/ec2/cloud.py", line 1291, in associate_address
address=public_ip)
File "/usr/lib/python2.7/dist-packages/nova/compute/api.py", line 100, in wrapped
return func(self, context, target, *args, **kwargs)
File "/usr/lib/python2.7/dist-packages/nova/compute/api.py", line 1638, in associate_floating_ip
floating_address=address, fixed_address=ips[0]['address'])
File "/usr/lib/python2.7/dist-packages/nova/network/api.py", line 146, in associate_floating_ip
'affect_auto_assigned': affect_auto_assigned}})
File "/usr/lib/python2.7/dist-packages/nova/rpc/__init__.py", line 68, in call
return _get_impl().call(context, topic, msg, timeout)
File "/usr/lib/python2.7/dist-packages/nova/rpc/impl_kombu.py", line 674, in call
return rpc_amqp.call(context, topic, msg, timeout, Connection.pool)
File "/usr/lib/python2.7/dist-packages/nova/rpc/amqp.py", line 338, in call
rv = list(rv)
File "/usr/lib/python2.7/dist-packages/nova/rpc/amqp.py", line 306, in __iter__
raise result
RemoteError: Remote error: FloatingIpAssociated Floating ip 172.31.237.80 is associated.
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