Add parent and abstract flags for diskimages

While YAML does have inbuilt support for anchors to greatly reduce
duplicated sections, anchors have no support for merging values.  For
diskimages, this can result in a lot of duplicated values for each
image which you can not otherwise avoid.

This provides two new values for diskimages; a "parent" and
"abstract".

Specifying a parent means you inherit all the configuration values
from that image.  Anything specified within the child image overwrites
the parent values as you would expect; caveats, as described in the
documentation, are that the elements field appends and the env-vars
field has update() semantics.

An "abstract" diskimage is not instantiated into a real image, it is
only used for configuration inheritance.  This way you can make a
abstrat "base" image with common values and inherit that everywhere
without having to worry about bringing in values you don't want.

You can also chain parents together and the inheritance flows through.

Documentation is updated, and several tests are added to ensure the
correct parenting, merging and override behaviour of the new values.

Change-Id: I170016ef7d8443b9830912b9b0667370e6afcde7

doc/source/configuration.rst

@@ -191,17 +191,17 @@ Options
 
    To remove a diskimage from the system entirely, remove all
    associated entries in :attr:`providers.[openstack].diskimages` and
-   remove its entry from `diskimages`.  All uploads will be deleted as
+   remove its entry from ``diskimages``.  All uploads will be deleted
-   well as the files on disk.
+   as well as the files on disk.
+
+   A sample configuration section is illustrated below.
 
    .. code-block:: yaml
 
       diskimages:
-        - name: ubuntu-precise
+        - name: base
-          pause: False
+          abstract: True
-          rebuild-age: 86400
           elements:
-            - ubuntu-minimal
             - vm
             - simple-init
             - openstack-repos
@@ -210,40 +210,44 @@ Options
             - cache-bindep
             - growroot
             - infra-package-needs
-          release: precise
-          username: zuul
           env-vars:
             TMPDIR: /opt/dib_tmp
             DIB_CHECKSUM: '1'
             DIB_IMAGE_CACHE: /opt/dib_cache
+
+        - name: ubuntu-bionic
+          parent: base
+          pause: False
+          rebuild-age: 86400
+          elements:
+            - ubuntu-minimal
+          release: bionic
+          username: zuul
+          env-vars:
             DIB_APT_LOCAL_CACHE: '0'
             DIB_DISABLE_APT_CLEANUP: '1'
             FS_TYPE: ext3
-        - name: ubuntu-xenial
+
+        - name: ubuntu-focal
+          base: ubuntu-bionic
+          release: focal
+          env-vars:
+            DIB_DISABLE_APT_CLEANUP: '0'
+
+        - name: centos-8
+          parent: base
           pause: True
           rebuild-age: 86400
           formats:
             - raw
             - tar
           elements:
-            - ubuntu-minimal
+            - centos-minimal
-            - vm
+            - epel
-            - simple-init
+          release: '8'
-            - openstack-repos
+          username: centos
-            - nodepool-base
-            - cache-devstack
-            - cache-bindep
-            - growroot
-            - infra-package-needs
-          release: precise
-          username: ubuntu
           env-vars:
-            TMPDIR: /opt/dib_tmp
+            FS_TYPE: xfs
-            DIB_CHECKSUM: '1'
-            DIB_IMAGE_CACHE: /opt/dib_cache
-            DIB_APT_LOCAL_CACHE: '0'
-            DIB_DISABLE_APT_CLEANUP: '1'
-            FS_TYPE: ext3
 
    Each entry is a dictionary with the following keys
 
@@ -254,6 +258,42 @@ Options
       Identifier to reference the disk image in
       :attr:`providers.[openstack].diskimages` and :attr:`labels`.
 
+   .. attr:: abstract
+      :type: bool
+      :default: False
+
+      An ``abstract`` entry is used to group common configuration
+      together, but will not create any actual image.  A ``diskimage``
+      marked as ``abstract`` should be inherited from in another
+      ``diskimage`` via its :attr:`diskimages.parent` attribute.
+
+      An `abstract` entry can have a :attr:`diskimages.parent`
+      attribute as well; values will merge down.
+
+   .. attr:: parent
+      :type: str
+
+      A parent ``diskimage`` entry to inherit from.  Any values from the
+      parent will be populated into this image.  Setting any fields in
+      the current image will override the parent values execept for
+      the following:
+
+      * :attr:`diskimages.env-vars`: new keys are additive, any
+        existing keys from the parent will be overwritten by values in
+        the current diskimage (i.e. Python `update()` semantics for a
+        dictionary).
+      * :attr:`diskimages.elements`: values are additive; the list of
+        elements from the parent will be extended with any values in
+        the current diskimage.  Note that the element list passed to
+        `diskimage-builder` is not ordered; elements specify their own
+        dependencies and `diskimage-builder` builds a graph from that,
+        not the command-line order.
+
+      Note that a parent ``diskimage`` may also have it's own parent,
+      creating a chain of inheritance.  See also
+      :attr:`diskimages.abstract` for defining common configuration
+      that does not create a diskimage.
+
    .. attr:: formats
       :type: list
 

nodepool/cmd/config_validator.py

@@ -42,10 +42,12 @@ class ConfigValidator:
 
         diskimage = {
             v.Required('name'): str,
+            'abstract': bool,
             'dib-cmd': str,
             'pause': bool,
             'elements': [str],
             'formats': [str],
+            'parent': str,
             'release': v.Any(str, int),
             'rebuild-age': int,
             'env-vars': {str: str},
@@ -121,6 +123,14 @@ class ConfigValidator:
                 errors = True
             diskimages[name] = diskimage
 
+        # Now check every parent is defined
+        for diskimage in config.get('diskimages', []):
+            if diskimage.get('parent', None):
+                if diskimage['parent'] not in diskimages:
+                    log.error("diskimage %s has non-existant parent: %s" %
+                              (diskimage['name'], diskimage['parent']))
+                    errors = True
+
         if errors is True:
             return 1
         else:

nodepool/config.py

@@ -98,28 +98,69 @@ class Config(ConfigValue):
         if not diskimages_cfg:
             return
 
+        all_diskimages = {}
+        non_abstract_diskimages = []
+
+        # create a dict and split out the abstract images which don't
+        # become final images, but can still be referenced as parent:
         for diskimage in diskimages_cfg:
             name = diskimage['name']
-            d = DiskImage(name)
+            all_diskimages[name] = diskimage
+            if not diskimage.get('abstract', False):
+                non_abstract_diskimages.append(diskimage)
+
+        def _set_from_config(diskimage, config):
+            build_timeout = config.get('build-timeout', None)
+            if build_timeout:
+                diskimage.build_timeout = build_timeout
+            dib_cmd = config.get('dib-cmd', None)
+            if dib_cmd:
+                diskimage.dib_cmd = dib_cmd
+            elements = config.get('elements', [])
+            diskimage.elements.extend(elements)
+            env_vars = config.get('env-vars', {})
+            diskimage.env_vars.update(env_vars)
+            image_types = config.get('formats', None)
+            if image_types:
+                diskimage.image_types = set(image_types)
+            pause = config.get('pause', None)
+            if pause:
+                diskimage.pause = pause
+            python_path = config.get('python-path', None)
+            if python_path:
+                diskimage.python_path = python_path
+            rebuild_age = config.get('rebuild-age', None)
+            if rebuild_age:
+                diskimage.rebuild_age = rebuild_age
+            release = config.get('release', None)
+            if release:
+                diskimage.release = release
+
+        def _merge_image_cfg(diskimage, parent):
+            parent_cfg = all_diskimages[parent]
+            if parent_cfg.get('parent', None):
+                _merge_image_cfg(diskimage, parent_cfg['parent'])
+            _set_from_config(diskimage, parent_cfg)
+
+        for cfg in non_abstract_diskimages:
+            d = DiskImage(cfg['name'])
+
+            # Walk the parents, if any, and set their values
+            if cfg.get('parent', None):
+                _merge_image_cfg(d, cfg.get('parent'))
+
+            # Now set our config, which overrides any values from
+            # parents.
+            _set_from_config(d, cfg)
 
-            if 'elements' in diskimage:
-                d.elements = u' '.join(diskimage['elements'])
-            else:
-                d.elements = ''
-            d.dib_cmd = str(diskimage.get('dib-cmd', 'disk-image-create'))
             # must be a string, as it's passed as env-var to
             # d-i-b, but might be untyped in the yaml and
             # interpreted as a number (e.g. "21" for fedora)
-            d.release = str(diskimage.get('release', ''))
+            d.release = str(d.release)
-            d.rebuild_age = int(diskimage.get('rebuild-age', 86400))
+
-            d.env_vars = diskimage.get('env-vars', {})
+            # This is expected as a space-separated string
-            if not isinstance(d.env_vars, dict):
+            d.elements = u' '.join(d.elements)
-                d.env_vars = {}
+
-            d.image_types = set(diskimage.get('formats', []))
-            d.pause = bool(diskimage.get('pause', False))
-            d.username = diskimage.get('username', 'zuul')
-            d.python_path = diskimage.get('python-path', 'auto')
-            d.build_timeout = diskimage.get('build-timeout', (8 * 60 * 60))
             self.diskimages[d.name] = d
 
     def setSecureDiskimageEnv(self, diskimages, secure_config_path):
@@ -172,18 +213,21 @@ class Label(ConfigValue):
 
 
 class DiskImage(ConfigValue):
+    BUILD_TIMEOUT = (8 * 60 * 60)  # 8 hours
+    REBUILD_AGE = (24 * 60 * 60)   # 24 hours
+
     def __init__(self, name):
         self.name = name
-        self.build_timeout = None
+        self.build_timeout = self.BUILD_TIMEOUT
-        self.dib_cmd = None
+        self.dib_cmd = 'disk-image-create'
-        self.elements = None
+        self.elements = []
-        self.env_vars = None
+        self.env_vars = {}
-        self.image_types = None
+        self.image_types = set([])
         self.pause = False
-        self.python_path = None
+        self.python_path = 'auto'
-        self.rebuild_age = None
+        self.rebuild_age = self.REBUILD_AGE
-        self.release = None
+        self.release = ''
-        self.username = None
+        self.username = 'zuul'
 
     def __eq__(self, other):
         if isinstance(other, DiskImage):

nodepool/tests/fake-image-create

@@ -58,11 +58,85 @@ while true ; do
     esac
 done
 
+ELEMENTS="$@"
+
 if [ -z "$outfile" ]; then
     echo "No output file specified."
     exit 1
 fi
 
+#
+#  WTF is this testing?  That we merge abstract diskimages correctly
+#  into children and append/override variables correctly.  The two
+#  images in the test config file
+#  (/nodepool/tests/fixtures/node_diskimage_parents.yaml) set
+#  PARENT_TEST_FLAG which we gate on here so we only run this for that
+#  test.  The diskimage layout when hitting this path is roughly like
+#  this:
+#
+#           %%%%% abstract-base %%%%%
+#           elements: fedora
+#           env:  TMPDIR, DIB_IMAGE_... (and so on)
+#                 PARENT_TEST_ENV_OVERRIDE=abstract-base
+#                  |       |
+#          |-------+        +-------|
+#          |                        |
+#          |                        |
+#          |     %%%%% abstract-intermediate %%%%%
+#          |     elements: intermediate
+#          |     env: PARENT_TEST_ENV_INTERMEDIATE=abstract-intermediate
+#          |                               |
+#          |                               |
+# %%%%% parent-image-1 %%%%%     %%%%% parent-image-2 %%%%%%
+# elements: vm                   elements: vm
+# env:  PARENT_TEST_FLAG=base   env:  PARENT_TEST_FLAG=intermediate
+#                                     PARENT_TEST_ENV_OVERRIDE=parent-image-2
+#
+# So for parent-image-1 we want to see elements "fedora vm" and for
+# parent-image-2 we want to see "fedora intermediate vm"; and similar
+# updates/overrides for the env-vars.
+#
+if [[ -n "${PARENT_TEST_FLAG}" ]]; then
+
+    if [[ "${PARENT_TEST_FLAG}" == "base" ]]; then
+        # Note we've already tested the base-defined env-vars like
+        # TMPDIR, DIB_*, etc. are merged because they're tested above.
+        if [[ "${ELEMENTS}" != "fedora vm" ]]; then
+            echo "Elements list did not merge correctly"
+            exit 1
+        else
+            echo "  -> Base elements list correctly merged"
+        fi
+
+    elif [[ "${PARENT_TEST_FLAG}" == "intermediate" ]]; then
+
+        if [[ "${ELEMENTS}" != "fedora intermediate vm" ]]; then
+            echo "Elements list did not merge correctly"
+            exit 1
+        else
+            echo "  -> Intermediate elements list correctly merged"
+        fi
+
+        if [[ "${PARENT_TEST_ENV_INTERMEDIATE}" != "abstract-intermediate" ]]; then
+            echo "Did not see intermediate env value in final job"
+            exit 1
+        else
+            echo "  -> Intermediate env value correctly merged"
+        fi
+
+        if [[ "${PARENT_TEST_ENV_OVERRIDE}" != "parent-image-2" ]]; then
+            echo "Final job did not override PARENT_TEST_ENV_OVERRIDE correctly"
+            exit 1
+        else
+            echo "  -> Env override correct"
+        fi
+    else
+        echo "Invalid PARENT_TEST_IMAGE?"
+        exit 1
+    fi
+
+fi
+
 # Tests can pause this script by creating this file before it runs.
 # No dib files should be created yet at the pause point.
 tmpdir=$(dirname $outfile)

nodepool/tests/fixtures/config_validate/missing_parent_diskimage.yaml

@@ -0,0 +1,209 @@
+elements-dir: /etc/nodepool/elements
+images-dir: /opt/nodepool_dib
+
+webapp:
+  port: 8005
+  listen_address: '0.0.0.0'
+
+zookeeper-servers:
+  - host: zk1.openstack.org
+    port: 2181
+    chroot: /test
+
+labels:
+  - name: trusty
+    max-ready-age: 3600
+    min-ready: 1
+  - name: trusty-2-node
+    min-ready: 0
+  - name: trusty-external
+    min-ready: 1
+  - name: trusty-static
+  - name: kubernetes-namespace
+  - name: pod-fedora
+  - name: openshift-project
+  - name: openshift-pod
+  - name: centos-ami
+
+providers:
+  - name: cloud1
+    driver: openstack
+    cloud: vanilla-cloud
+    region-name: 'vanilla'
+    boot-timeout: 120
+    max-concurrency: 10
+    launch-retries: 3
+    port-cleanup-interval: 600
+    rate: 1
+    diskimages:
+      - name: trusty
+    pools:
+      - name: main
+        max-servers: 184
+        auto-floating-ip: True
+        host-key-checking: True
+        node-attributes:
+          key1: value1
+          key2: value2
+        networks:
+          - public
+          - private
+        labels:
+          - name: trusty
+            diskimage: trusty
+            min-ram: 8192
+            console-log: True
+            networks:
+              - public
+          - name: trusty-2-node
+            diskimage: trusty
+            min-ram: 8192
+            boot-from-volume: True
+            volume-size: 100
+            instance-properties:
+              a_key: a_value
+              b_key: b_value
+            userdata: |
+              #cloud-config
+              password: password
+              chpasswd: { expire: False }
+              ssh_pwauth: True
+              hostname: test
+
+  - name: cloud2
+    driver: openstack
+    cloud: chocolate-cloud
+    region-name: 'chocolate'
+    boot-timeout: 120
+    rate: 0.001
+    port-cleanup-interval: 0
+    post-upload-hook: /usr/bin/upload-hook
+    diskimages:
+      - name: trusty
+        pause: False
+        connection-type: ssh
+        connection-port: 22
+    cloud-images:
+      - name: trusty-unmanaged
+        config-drive: true
+      - name: windows-unmanaged
+        username: winzuul
+        python-path: A:/python3.7.exe
+        connection-type: winrm
+        connection-port: 5986
+    pools:
+      - name: main
+        max-servers: 184
+        auto-floating-ip: False
+        host-key-checking: False
+        security-groups:
+          - zuul_sg
+        labels:
+          - name: trusty
+            diskimage: trusty
+            min-ram: 8192
+            networks:
+              - public
+              - private
+          - name: trusty-2-node
+            diskimage: trusty
+            min-ram: 8192
+          - name: trusty-external
+            cloud-image: trusty-unmanaged
+            min-ram: 8192
+
+  - name: static-rack
+    driver: static
+    pools:
+      - name: main
+        nodes:
+          - name: trusty.example.com
+            labels: trusty-static
+            host-key: fake-key
+            timeout: 13
+            connection-port: 22022
+            username: zuul
+            max-parallel-jobs: 1
+
+  - name: kubespray
+    driver: kubernetes
+    context: admin-cluster.local
+    pools:
+      - name: main
+        labels:
+          - name: kubernetes-namespace
+            type: namespace
+          - name: pod-fedora
+            type: pod
+            image: docker.io/fedora:28
+
+  - name: openshift
+    driver: openshift
+    context: "/hostname:8443/self-provisioner-service-account"
+    pools:
+      - name: main
+        labels:
+          - name: openshift-project
+            type: project
+          - name: openshift-pod
+            type: pod
+            image: docker.io/fedora:28
+            python-path: /usr/bin/python3
+            memory: 512
+            cpu: 2
+
+  - name: ec2-us-east-2
+    driver: aws
+    region-name: us-east-2
+    profile-name: default
+    cloud-images:
+      - name: centos-ami
+        image-id: ami-cfdafaaa
+        username: centos
+    pools:
+      - name: main
+        max-servers: 42
+        security-group-id: sg-8bfe86352e334a80a
+        subnet-id: subnet-bb3605b5f0fa40e1b
+        labels:
+          - name: centos-ami
+            cloud-image: centos-ami
+            instance-type: t2.micro
+            key-name: zuul
+            volume-type: gp2
+            volume-size: 80
+
+  - name: openshift-single-project
+    driver: openshiftpods
+    context: "/hostname:8443/developer"
+    pools:
+      - name: project-name
+        labels:
+          - name: openshift-pod
+            image: docker.io/fedora:28
+
+diskimages:
+  - name: a_parent
+  - name: a_child
+    parent: a_parent
+
+  - name: trusty
+    parent: this_does_not_exist
+    formats:
+      - tar
+    pause: False
+    elements:
+      - ubuntu
+      - vm
+      - openstack-repos
+      - puppet
+      - nodepool-base
+      - cache-devstack
+    release: trusty
+    rebuild-age: 3600
+    build-timeout: 3600
+    python-path: /bin/python3.6
+    env-vars:
+      TMPDIR: /opt/dib_tmp
+      DIB_IMAGE_CACHE: /opt/dib_cache
+      QEMU_IMG_OPTIONS: compat=0.10

nodepool/tests/fixtures/node_diskimage_parents.yaml

@@ -0,0 +1,85 @@
+elements-dir: .
+images-dir: '{images_dir}'
+build-log-dir: '{build_log_dir}'
+
+zookeeper-servers:
+  - host: {zookeeper_host}
+    port: {zookeeper_port}
+    chroot: {zookeeper_chroot}
+
+labels:
+  - name: fake-image-parent-1
+    min-ready: 1
+  - name: fake-image-parent-2
+    min-ready: 1
+
+providers:
+  - name: fake-provider-1
+    cloud: fake
+    driver: fake
+    region-name: fake-region
+    rate: 0.0001
+    diskimages:
+      - name: parent-image-1
+    pools:
+      - name: main
+        max-servers: 96
+        labels:
+          - name: fake-image-parent-1
+            diskimage: parent-image-1
+            min-ram: 8192
+  - name: fake-provider-2
+    cloud: fake
+    driver: fake
+    region-name: fake-region
+    rate: 0.0001
+    diskimages:
+      - name: parent-image-2
+    pools:
+      - name: main
+        max-servers: 96
+        labels:
+          - name: fake-image-parent-2
+            diskimage: parent-image-2
+            min-ram: 8192
+
+diskimages:
+  - name: abstract-base
+    abstract: True
+    elements:
+      - fedora
+    env-vars:
+      TMPDIR: /opt/dib_tmp
+      DIB_IMAGE_CACHE: /opt/dib_cache
+      DIB_CLOUD_IMAGES: http://download.fedoraproject.org/pub/fedora/linux/releases/test/21-Beta/Cloud/Images/x86_64/
+      BASE_IMAGE_FILE: Fedora-Cloud-Base-20141029-21_Beta.x86_64.qcow2
+      PARENT_TEST_ENV_OVERRIDE: abstract-base
+
+  - name: abstract-intermediate
+    abstract: True
+    parent: abstract-base
+    elements:
+      - intermediate
+    env-vars:
+      PARENT_TEST_ENV_INTERMEDIATE: abstract-intermediate
+
+  - name: parent-image-1
+    parent: abstract-base
+    elements:
+      # - fedora : should merge from parent!
+      - vm
+    release: 21
+    dib-cmd: nodepool/tests/fake-image-create
+    env-vars:
+      PARENT_TEST_FLAG: 'base'
+
+  - name: parent-image-2
+    parent: abstract-intermediate
+    elements:
+      # - fedora : should merge from parent
+      - vm
+    release: 21
+    dib-cmd: nodepool/tests/fake-image-create
+    env-vars:
+      PARENT_TEST_FLAG: 'intermediate'
+      PARENT_TEST_ENV_OVERRIDE: parent-image-2

nodepool/tests/unit/test_builder.py

@@ -24,6 +24,7 @@ from pathlib import Path
 from nodepool import builder, exceptions, tests
 from nodepool.driver.fake import provider as fakeprovider
 from nodepool import zk
+from nodepool.config import Config
 from nodepool.nodeutils import iterate_timeout
 
 
@@ -98,6 +99,89 @@ class TestNodepoolBuilderDibImage(tests.BaseTestCase):
         self.assertRaises(exceptions.BuilderError, image.to_path, '/imagedir/')
 
 
+class TestNodepoolBuilderImageInheritance(tests.BaseTestCase):
+    def test_parent_job(self):
+        config = Config()
+        diskimages = [
+            {
+                'name': 'parent',
+                'dib-cmd': 'parent-dib-cmd',
+                'elements': ['a', 'b'],
+                'env-vars': {
+                    'A': 'foo',
+                    'B': 'bar',
+                },
+                'release': 21,
+            },
+            {
+                'name': 'child',
+                'parent': 'parent',
+                'dib-cmd': 'override-dib-cmd',
+                'elements': ['c'],
+                'env-vars': {
+                    'A': 'override_foo',
+                    'C': 'moo'
+                },
+            },
+
+        ]
+        config.setDiskImages(diskimages)
+        parsed = config.diskimages['child']
+        self.assertEqual(parsed.dib_cmd, 'override-dib-cmd')
+        self.assertEqual(parsed.release, '21')
+        self.assertEqual(parsed.elements, 'a b c')
+        self.assertDictEqual({
+            'A': 'override_foo',
+            'B': 'bar',
+            'C': 'moo',
+        }, parsed.env_vars)
+
+    def test_abstract_jobs(self):
+        config = Config()
+        diskimages = [
+            {
+                'name': 'abstract',
+                'abstract': True,
+                'elements': ['a', 'b'],
+                'env-vars': {
+                    'A': 'foo',
+                    'B': 'bar',
+                },
+            },
+            {
+                'name': 'another-abstract',
+                'abstract': True,
+                'parent': 'abstract',
+                'elements': ['c'],
+                'env-vars': {
+                    'A': 'override_abstract',
+                    'C': 'moo'
+                },
+            },
+            {
+                'name': 'job',
+                'parent': 'another-abstract',
+                'elements': ['d'],
+                'dib-cmd': 'override-dib-cmd',
+                'env-vars': {
+                    'A': 'override_foo_again',
+                    'D': 'zoo'
+                },
+            },
+
+        ]
+        config.setDiskImages(diskimages)
+        parsed = config.diskimages['job']
+        self.assertEqual(parsed.dib_cmd, 'override-dib-cmd')
+        self.assertEqual(parsed.elements, 'a b c d')
+        self.assertDictEqual({
+            'A': 'override_foo_again',
+            'B': 'bar',
+            'C': 'moo',
+            'D': 'zoo',
+        }, parsed.env_vars)
+
+
 class TestNodePoolBuilder(tests.DBTestCase):
 
     def test_start_stop(self):
@@ -399,6 +483,12 @@ class TestNodePoolBuilder(tests.DBTestCase):
         self.assertReportedStat('nodepool.dib_image_build.'
                                 'fake-image-vhd.vhd.size', '4096', 'g')
 
+    def test_diskimage_build_parents(self):
+        configfile = self.setup_config('node_diskimage_parents.yaml')
+        self.useBuilder(configfile)
+        self.waitForBuild('parent-image-1', '0000000001')
+        self.waitForBuild('parent-image-2', '0000000001')
+
     @mock.patch('select.poll')
     def test_diskimage_build_timeout(self, mock_poll):
         configfile = self.setup_config('diskimage_build_timeout.yaml')

nodepool/tests/unit/test_config_validator.py

@@ -66,6 +66,15 @@ class TestConfigValidation(tests.BaseTestCase):
         ret = validator.validate()
         self.assertEqual(ret, 1)
 
+    def test_missing_parent_diskimage(self):
+        config = os.path.join(os.path.dirname(tests.__file__),
+                              'fixtures', 'config_validate',
+                              'missing_parent_diskimage.yaml')
+
+        validator = ConfigValidator(config)
+        ret = validator.validate()
+        self.assertEqual(ret, 1)
+
     def test_schema(self):
         config = os.path.join(os.path.dirname(tests.__file__),
                               'fixtures', 'config_validate',

releasenotes/notes/diskimages-parent-182d518232b5649b.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Entries in the `diskimages` section can now specify a parent image
+    to inherit configuration values from.  You can also specify images
+    for configuration use only as `abstract` to consolidate
+    common values.