downpour/doc/source/usage.rst

Usage

Downpour uses a four step process. Between each step it is possible to stop and modify the data that has been prepared to pass to the next step.

1. Identify Resources to Export

The first phase of using Downpour is to identify exactly what resources will be exported from the cloud to build the resource file. This step can be performed by hand by creating the required input file in a text editor, or the file can be build using the query command.

The resource file is a YAML file with sections for the principle resource types, keypairs, images, volumes, and servers. Resources are identified by name, and may also include extra parameters to control how the export and re-import operations are performed. For example, this resource file causes the downpour-demo-tiny server to be exported but when it is recreated a different ssh key is used to provide access to log in.

../../demo/tiny-resources.yml

The downpour query command also can be used to find resources visible in the cloud, and add them to the resource file. It supports wildcard patterns in names and other criteria for filtering resources. For example, this command finds all servers with "tiny" in their name.

$ downpour query --server-name '*tiny*' export.yml

resource_file includes more details about resource files.

2. Exporting Resources

The second phase of operation is to actually export the resources from the cloud using downpour export, passing the resource file as input. Downpour starts by processing the resources listed in the file explicitly, and identifies any extra dependencies needed to recreate the configuration of those resources. For example, the networks, subnets, and security groups used by a server are exported automatically, as are the volumes attached to the server.

$ downpour export export.yml ./export/

The output for the export process is an Ansible playbook to recreate the resources, with all relationships intact. For images, volumes, and servers with the save-state flag set to true, the content of the resource will be downloaded and saved to the output directory where it can be used to recreate the resource.

3. Importing Resources

The import phase uses ansible-playbook to run the playbook created by the exporter.

Note

Although Downpour currently requires Python 3.5 or greater, Ansible is a Python 2.x application. If you are using pip and virtualenv to install the tools, you will need to install them in separate virtual environments.

Ansible uses os-client-config for settings related to accessing the cloud. The simplest way to configure the cloud is via a clouds.yaml file, but any mechanism supported by Ansible will work. The credentials used for the import phase do not need to be the same as the export phase. In fact, they're likely to be completely different because they will refer to a separate cloud's API endpoints.

Downpour supports some customizations during export, such as changing the ssh key to be used for accessing a server. Other changes can be made by editing the playbook before running it.

The playbook produced by Downpour creates each resource, then adds a line to a file uuids.csv to map the UUID in the source cloud to the UUID in the target cloud. This file may be useful for updating scripts or other configuration that rely on the UUID instead of a unique name for the resource.

"Resource Type","Resource Name","Old","New"
"security group","downpour-demo","6deea469-54bd-4846-b12a-79fa6b482280","a4b80ffc-bc51-485c-915a-9ba9a7b4dcf0"
"volume","downpour-demo-tiny","256868c6-441f-4cd3-96fd-bda92c33822c","62e5616c-9a8c-44e2-bd14-4685b905ea94"
"security group","downpour-demo","3c7dcb77-d9ac-4af1-ba95-3f5d89a85227","a4b80ffc-bc51-485c-915a-9ba9a7b4dcf0"
"volume","downpour-demo-tiny","a6192546-c36e-4bee-ad00-8229e0b0efc5","62e5616c-9a8c-44e2-bd14-4685b905ea94"
"network","private","56a86bdb-13b2-4c9f-b8f5-a942d52602b5","f3027502-e4a2-4610-81fb-c6df99ead5c3"
"subnet","ipv6-private-subnet","8d736fe4-6b8f-4bf5-a38e-b511dce21f7f","01025e33-703b-4aa4-b6ec-80036bb3679b"
"subnet","private-subnet","e6baf9f4-09b5-4292-8236-3cca609ec2a3","2f9a1686-8125-4316-acd3-dbee51c44c1d"
"keypair","downpour-demo","downpour-demo","downpour-demo"
"image","cirros-0.3.5-x86_64-disk","570ec7bd-011b-4fbe-9968-626225654a7f","570ec7bd-011b-4fbe-9968-626225654a7f"

4. Decomissioning Resources

Downpour is not a live-migration tool, and it does not delete any resources from the source cloud. This allows you to perform application-specific migration (such as a final database sync) before updating any load balancers or DNS records and deleting old information.