Add metadata interface for instance data

Some plugins, like the userdata execution plugin, need a standard model
for the instance data, which can be applied by templating engines like
jinja to the userdata.

This way, a user can use this feature to customize her userdata scripts
with values that are specific to that instance runtime env or cloud platform.

The instance data structure is based on the cloud-init specifications:
https://cloudinit.readthedocs.io/en/latest/topics/instancedata.html

The v1 namespace contains a subset of the cloud-init specs for the instance
data.

The ds.meta_data namespace contains all the values the v1 namespace
contains, in order to be compatible with cloud-init, plus a subset
of other instance data.

Change-Id: I5c529498f06fe3c86f7fa3c20fdf3091840c4041

cloudbaseinit/metadata/services/base.py

@@ -14,6 +14,7 @@
 
 
 import abc
+import copy
 import gzip
 import io
 import time
@@ -221,6 +222,45 @@ class BaseMetadataService(object):
     def get_ephemeral_disk_data_loss_warning(self):
         raise NotExistingMetadataException()
 
+    def get_instance_data(self):
+        """Returns a dictionary with instance data from the metadata source
+
+        The instance data structure is based on the cloud-init specifications:
+        https://cloudinit.readthedocs.io/en/latest/topics/instancedata.html
+
+        The v1 namespace contains a subset of the cloud-init standard
+        for the instance data. In the future, it should reach parity with the
+        cloud-init standard.
+
+        The ds.meta_data namespace contains all the values the v1 namespace
+        contains, in order to be compatible with cloud-init, plus a subset of
+        other instance data.
+        The ds namespace can change without prior notice and should not be
+        used in production.
+        """
+
+        instance_id = self.get_instance_id()
+        hostname = self.get_host_name()
+
+        v1_data = {
+            "instance_id": instance_id,
+            "local_hostname": hostname,
+            "public_ssh_keys": self.get_public_keys()
+        }
+
+        # Copy the v1 data to the ds.meta_data and add more fields
+        ds_meta_data = copy.deepcopy(v1_data)
+        ds_meta_data.update({
+            "hostname": hostname
+        })
+
+        return {
+            "v1": v1_data,
+            "ds": {
+                "meta_data": ds_meta_data,
+            }
+        }
+
 
 class BaseHTTPMetadataService(BaseMetadataService):
 

cloudbaseinit/tests/metadata/services/test_base.py

@@ -61,6 +61,38 @@ class TestBase(unittest.TestCase):
         result = self._service.get_user_pwd_encryption_key()
         self.assertEqual(result, mock_get_public_keys.return_value[0])
 
+    @mock.patch('cloudbaseinit.metadata.services.base.'
+                'BaseMetadataService.get_public_keys')
+    @mock.patch('cloudbaseinit.metadata.services.base.'
+                'BaseMetadataService.get_host_name')
+    @mock.patch('cloudbaseinit.metadata.services.base.'
+                'BaseMetadataService.get_instance_id')
+    def test_get_instance_data(self, mock_instance_id, mock_hostname,
+                               mock_public_keys):
+        fake_instance_id = 'id'
+        mock_instance_id.return_value = fake_instance_id
+        fake_hostname = 'host'
+        mock_hostname.return_value = fake_hostname
+        fake_keys = ['ssh1', 'ssh2']
+        mock_public_keys.return_value = fake_keys
+
+        expected_response = {
+            'v1': {
+                "instance_id": fake_instance_id,
+                "local_hostname": fake_hostname,
+                "public_ssh_keys": fake_keys
+            },
+            'ds': {
+                'meta_data': {
+                    "instance_id": fake_instance_id,
+                    "local_hostname": fake_hostname,
+                    "public_ssh_keys": fake_keys,
+                    "hostname": fake_hostname
+                },
+            }
+        }
+        self.assertEqual(expected_response, self._service.get_instance_data())
+
 
 class TestBaseHTTPMetadataService(unittest.TestCase):