openstack: Allow discovery in init-local using dhclient in a sandbox.

Network has not yet been configured in the init-local stage so the
openstack datasource will use dhcp-client to temporarily obtain an ipv4
address and query the metadata service at http://169.254.169.254 to get
network_data.json configuration. If present, the datasource will return
network_config version 1 config based on that network_data.json content.
Previously OpenStack datasource only setup dhcp on the fallback interface
so this represents a change in behavior to react to the full config
provided by openstack.

Also significant to OpenStack is the separation of a _crawl_data operation
from get_data(). crawl_data walks the available metadata services and
returns a dict of discovered content. get_data consumes the crawled_data,
 caches it in the datasource and reacts to that data.
/run/cloud-init/instance-data.json now published network_data.json or
ec2_metadata key if that data is present on any datasource.

The main reasons for the separation of crawl from get_data:
 * Enable performance metrics of cloud-init's metadata crawls on each
 * Enable cloud-init modules and scripts to query and consume metadata
   content which may have updated/changed after cloud-init's initial cache
   during instance boot. (Think hotplug)

Also generalize common logic to base DataSource class/module:
 * Move to a common UNSET variable up into base datasource module fix EC2,
   ConfigDrive, OpenStack, SmartOS to use the global.
 * Drop get_url_settings from Ec2, CloudStack and OpenStack and generalize
   DataSource.get_url_params(). Allow subclasses to override url_max_wait,
   url_timeout and url_retries params.
 * Rename get_network_metadata bool to perform_dhcp_setup as it designates
   whether EphemeralDHCPv4 setup is required before crawling metadata.

LP: #1749717

0 files changed, 0 insertions, 0 deletions