Last resort fallback to find a partition

Falls back to attempt to use findfs to locate
a UUID or PARTUUID match as opposed to trying to
list and enumerate through lsblk output.

Can confirm that tinycore 8.x's findfs binary works
expected.

Story: 2006724
Task: 37141

Change-Id: I4d488e4a1ab680eb1353b158c3339cb30b056ada

ironic_python_agent/extensions/image.py

@@ -75,6 +75,9 @@ def _get_partition(device, uuid):
                 part[key] = val.strip()
             # Ignore non partition
             if part.get('TYPE') != 'part':
+                # NOTE(TheJulia): This techincally creates an edge failure
+                # case where a filesystem on a whole block device sans
+                # partitioning would behave differently.
                 continue
 
             if part.get('UUID') == uuid:
@@ -86,6 +89,28 @@ def _get_partition(device, uuid):
                           "%(dev)s", {'uuid': uuid, 'dev': device})
                 return '/dev/' + part.get('KNAME')
         else:
+            # NOTE(TheJulia): We may want to consider moving towards using
+            # findfs in the future, if we're comfortable with the execution
+            # and interaction. There is value in either way though.
+            try:
+                findfs, stderr = utils.execute('findfs', 'UUID=%s' % uuid)
+                return findfs.strip()
+            except processutils.ProcessExecutionError as e:
+                LOG.debug('First fallback detection attempt for locating '
+                          'partition via UUID %(uuid)s failed. '
+                          'Error: %(err)s',
+                          {'uuid': uuid,
+                           'err': e})
+                try:
+                    findfs, stderr = utils.execute(
+                        'findfs', 'PARTUUID=%s' % uuid)
+                    return findfs.strip()
+                except processutils.ProcessExecutionError as e:
+                    LOG.debug('Secondary fallback detection attempt for '
+                              'locating partition via UUID %(uuid)s failed. '
+                              'Error: %(err)s',
+                              {'uuid': uuid,
+                               'err': e})
             error_msg = ("No partition with UUID %(uuid)s found on "
                          "device %(dev)s" % {'uuid': uuid, 'dev': device})
             LOG.error(error_msg)

ironic_python_agent/tests/unit/extensions/test_image.py

@@ -368,7 +368,10 @@ class TestImageExtension(base.IronicAgentTest):
         lsblk_output = ('''KNAME="test" UUID="" TYPE="disk"
         KNAME="test1" UUID="256a39e3-ca3c-4fb8-9cc2-b32eec441f47" TYPE="part"
         KNAME="test2" UUID="" TYPE="part"''')
-        mock_execute.side_effect = (None, None, [lsblk_output])
+        mock_execute.side_effect = (
+            None, None, [lsblk_output],
+            processutils.ProcessExecutionError('boom'),
+            processutils.ProcessExecutionError('kaboom'))
 
         self.assertRaises(errors.DeviceNotFound,
                           image._get_partition, self.fake_dev,
@@ -381,6 +384,31 @@ class TestImageExtension(base.IronicAgentTest):
         mock_execute.assert_has_calls(expected)
         self.assertFalse(mock_dispatch.called)
 
+    @mock.patch.object(hardware, 'is_md_device', autospec=True)
+    def test__get_partition_fallback_partuuid(self, mock_is_md_device,
+                                              mock_execute, mock_dispatch):
+        mock_is_md_device.side_effect = [False]
+        lsblk_output = ('''KNAME="test" UUID="" TYPE="disk"
+        KNAME="test1" UUID="256a39e3-ca3c-4fb8-9cc2-b32eec441f47" TYPE="part"
+        KNAME="test2" UUID="" TYPE="part"''')
+        findfs_output = ('/dev/loop0\n', None)
+        mock_execute.side_effect = (
+            None, None, [lsblk_output],
+            processutils.ProcessExecutionError('boom'),
+            findfs_output)
+
+        result = image._get_partition(self.fake_dev, self.fake_root_uuid)
+        self.assertEqual('/dev/loop0', result)
+        expected = [mock.call('partx', '-u', self.fake_dev, attempts=3,
+                              delay_on_retry=True),
+                    mock.call('udevadm', 'settle'),
+                    mock.call('lsblk', '-PbioKNAME,UUID,PARTUUID,TYPE',
+                              self.fake_dev),
+                    mock.call('findfs', 'UUID=%s' % self.fake_root_uuid),
+                    mock.call('findfs', 'PARTUUID=%s' % self.fake_root_uuid)]
+        mock_execute.assert_has_calls(expected)
+        self.assertFalse(mock_dispatch.called)
+
     @mock.patch.object(hardware, 'is_md_device', autospec=True)
     def test__get_partition_command_fail(self, mock_is_md_device,
                                          mock_execute, mock_dispatch):

releasenotes/notes/fallback-to-findfs-59abde55221e1e84.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixes an issue with the tinyIPA CI testing image by providing a fallback
+    root volume uuid detection method via the ``findfs`` utility, which is
+    also already packaged in most distributions with ``lsblk``.
+
+    This fallback was necesary as the ``lsblk`` command in ``TinyCore`` Linux,
+    upon which TinyIPA is built, does not return data as expected for
+    volume UUID values.