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=========================================================================
 Implement BlockDeviceMappings for AWS::AutoScaling::LaunchConfiguration
=========================================================================

Include the URL of your launchpad blueprint:

https://blueprints.launchpad.net/heat/+spec/implement-launchconfiguration-bdm

We should support the BlockDeviceMappings for AWS::AutoScaling::LaunchConfiguration
resource to be compatible with AWSCloudFormation. And therefore, user can specify volumes
to attach to instances while AutoScalingGroup/InstanceGroup creation.

Problem description
===================

Now in Heat, the AWS::AutoScaling::LaunchConfiguration resource doesn't implement
'BlockDeviceMappings' property to indicate the volumes to be attached. There are
two problems:

1. First, it's incompatible with AWSCloudFormation. In AWSCloudFormation,
'BlockDeviceMappings' support the 'SnapshotId', user can specify a snapshot,
then a volume will be created from the snapshot, and the volume will be attached
to the instance.

http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-launchconfig.html

2. Second, user can't specify volumes to be attached to instances which in
AutoScalingGroup/InstanceGroup while creation.

So, we should support the 'BlockDeviceMappings' for AWS::AutoScaling::LaunchConfiguration.

Proposed change
===============

1. Implement 'BlockDeviceMappings' property for AWS::AutoScaling::LaunchConfiguration resource,
   specially in which user can specify the 'SnapshotId'.

Alternatives
------------

None

Implementation
==============

Assignee(s)
-----------

Primary assignee:
  <huangtianhua>

Milestones
----------

Target Milestone for completion:
  Juno-2

Work Items
----------

1. Support the BlockDeviceMappings for AWS::AutoScaling::LaunchConfiguration resource
2. Add UT/Tempest for the change
3. Add a template for AWS::AutoScaling::LaunchConfiguration with BlockDeviceMappings

Dependencies
============

https://blueprints.launchpad.net/heat/+spec/implement-ec2instance-bdm