Merge lp:~mvo/ubuntu-system-image/machine-id-fallback into lp:~registry/ubuntu-system-image/client

[Michael Vogt]

This branch adds support for both /etc/machine-id and /var/lib/dbus/machine-id as the later is taking over (see also freedesktop bug https://bugs.freedesktop.org/show_bug.cgi?id=85572 - waiting for final confirmation from upstream though).

[Barry Warsaw (barry)]

Thanks Michael. I had to port this branch to s-i 3.0, which has changed quite a few things as to make this a non-trivial merge. But I copied your implementation in spirit so you get credit. :)

review: Approve

=== modified file 'systemimage/helpers.py'
--- systemimage/helpers.py	2014-09-16 20:06:56 +0000
+++ systemimage/helpers.py	2014-11-04 17:13:40 +0000
@@ -47,7 +47,8 @@
 
 
 LAST_UPDATE_FILE = '/userdata/.last_update'
-UNIQUE_MACHINE_ID_FILE = '/var/lib/dbus/machine-id'
+# systemd is taking over
+UNIQUE_MACHINE_ID_FILES = ['/var/lib/dbus/machine-id', '/etc/machine-id']
 DEFAULT_DIRMODE = 0o02700
 MiB = 1 << 20
 EMPTYSTRING = ''
@@ -275,8 +276,11 @@
 def phased_percentage(*, reset=False):
     global _pp_cache
     if _pp_cache is None:
-        with open(UNIQUE_MACHINE_ID_FILE, 'rb') as fp:
-            data = fp.read()
+        for f in UNIQUE_MACHINE_ID_FILES:
+            if os.path.exists(f):
+                with open(f, 'rb') as fp:
+                    data = fp.read()
+                break
         now = str(time.time()).encode('us-ascii')
         r = random.Random()
         r.seed(data + now)

=== modified file 'systemimage/tests/test_helpers.py'
--- systemimage/tests/test_helpers.py	2014-09-16 20:06:56 +0000
+++ systemimage/tests/test_helpers.py	2014-11-04 17:13:40 +0000
@@ -276,25 +276,26 @@
 class TestPhasedPercentage(unittest.TestCase):
     def setUp(self):
         phased_percentage(reset=True)
+        self.tmpdir = tempfile.mkdtemp()
+        self.machine_id = os.path.join(self.tmpdir, 'machine-id')
+        with open(self.machine_id, 'wb') as fp:
+            fp.write(b'0123456789abcdef\n')
 
     def tearDown(self):
         phased_percentage(reset=True)
+        shutil.rmtree(self.tmpdir)
 
     def test_phased_percentage(self):
         # This function returns a percentage between 0 and 100.  If this value
         # is greater than a similar value in the index.json's 'image' section,
         # that image is completely ignored.
         with ExitStack() as stack:
-            tmpdir = stack.enter_context(temporary_directory())
-            path = os.path.join(tmpdir, 'machine-id')
             stack.enter_context(patch(
-                'systemimage.helpers.UNIQUE_MACHINE_ID_FILE',
-                path))
+                'systemimage.helpers.UNIQUE_MACHINE_ID_FILES',
+                [self.machine_id]))
             stack.enter_context(patch(
                 'systemimage.helpers.time.time',
                 return_value=1380659512.983512))
-            with open(path, 'wb') as fp:
-                fp.write(b'0123456789abcdef\n')
             self.assertEqual(phased_percentage(), 81)
             # The value is cached, so it's always the same for the life of the
             # process, at least until we reset it.
@@ -303,25 +304,34 @@
     def test_phased_percentage_reset(self):
         # Test the reset API.
         with ExitStack() as stack:
-            tmpdir = stack.enter_context(temporary_directory())
-            path = os.path.join(tmpdir, 'machine-id')
             stack.enter_context(patch(
-                'systemimage.helpers.UNIQUE_MACHINE_ID_FILE',
-                path))
+                'systemimage.helpers.UNIQUE_MACHINE_ID_FILES',
+                [self.machine_id]))
             stack.enter_context(patch(
                 'systemimage.helpers.time.time',
                 return_value=1380659512.983512))
-            with open(path, 'wb') as fp:
-                fp.write(b'0123456789abcdef\n')
             self.assertEqual(phased_percentage(), 81)
             # The value is cached, so it's always the same for the life of the
             # process, at least until we reset it.
-            with open(path, 'wb') as fp:
+            with open(self.machine_id, 'wb') as fp:
                 fp.write(b'x0123456789abcde\n')
             self.assertEqual(phased_percentage(reset=True), 81)
             # The next one will have a different value.
             self.assertEqual(phased_percentage(), 17)
 
+    def test_phased_percentage_unique_fallback(self):
+        # ensure that the fallback for
+        #  systemimage.helpers.UNIQUE_MACHINE_ID_FILES
+        # works
+        with ExitStack() as stack:
+            stack.enter_context(patch(
+                'systemimage.helpers.UNIQUE_MACHINE_ID_FILES',
+                ['/xxx/does-not-exists', self.machine_id]))
+            stack.enter_context(patch(
+                'systemimage.helpers.time.time',
+                return_value=1380659512.983512))
+            self.assertEqual(phased_percentage(), 81)
+
 
 class TestSignature(unittest.TestCase):
     def test_calculate_signature(self):