Heat/ApplicationDeployment

https://wiki.openstack.org/wiki/Heat/ApplicationDeployment 

Walk-through in a stack's lifetime

• The user calls the Heat API to create a stack ("heat stack-create ... myStack")
• Heat engine generates a mime multipart data blob that will be consumed by cloud-init
• Heat engine asks nova to create an instance with the cloud-init data
• Nova selects a compute node to run the instance with the cloud-init data
• When the instance boots up, it runs the cloud-init script:

• Download the data from the metadata server
• Splits the multiple parts into the /var/lib/cloud/ directory
• Run the different cloud-init parts (resize the root filesystem, set the hostname, install the user's SSH key, etc.)
• Runs the user's script (located at /var/lib/cloud/data/cfn-userdata), it can be any kind of script (Bash, Python, etc.) but at some point this script should call cfn-init.

• cfn-init loads /var/lib/cloud/data/cfn-init-data (a copy of the Metadata->AWS::CloudFormation::Init->Config attribute from the AWS template) and can install packages, setup users & groups, create files, etc.

Note that heat-cfntools leverage the boto library and that the boto configuration is stored at /var/lib/heat-cfntools/cfn-boto-cfg on the instance.

Troubleshooting

If you can logged into the instance, look at the following files:

• /var/log/cloud-init.log => cloud-init logs
• /var/log/part-handler.log => logs of the Heat-specific script managing data with content-type=text/x-cfninitdata
• /var/log/heat-provision.log => logs of the user's script including cfn-init logs

You can also query the metadata server for the user's data generated by Heat: