Propagate qemu-img errors to compute manager

When qemu-img is called with oslo_concurrency.process_utils.execute
the ProcessExecutionError was raised when qemu-img either fails to
execute or has a non-zero exit code. This error did not propagate
up to the compute manager with any meaningful information meaning
that if an instance build fails the error message is the generic
"There are not enough hosts available".

This change captures ProcessExecutionError and re-raises the
exception as either InvalidDiskInfo (in qemu_img_info) or
ImageUnacceptable (in convert_image and fetch_to_raw) and makes the
manager accept this as a cause for a BuildAbortException on the
logic that if the image is bad, things are dire, let's bail.

Based on the code in qemu_img_info it appears there was a
misunderstanding of how process_utils.execute behaves so it seems
likely this problem is present elsewhere in the code. This change
attempts to only address the issue as it shows up on the new
instance path described in the related bug.

Conflicts:
	nova/virt/images.py

Change-Id: I4fa1c258db58c70dfbf0178b7bb13978fda3a11f
Closes-Bug: #1436166
(cherry picked from commit 9a4ecfd96d)

nova/compute/manager.py

@@ -2045,7 +2045,8 @@ class ComputeManager(manager.Manager):
         except (exception.FlavorDiskTooSmall,
                 exception.FlavorMemoryTooSmall,
                 exception.ImageNotActive,
-                exception.ImageUnacceptable) as e:
+                exception.ImageUnacceptable,
+                exception.InvalidDiskInfo) as e:
             self._notify_about_instance_usage(context, instance,
                     'create.error', fault=e)
             raise exception.BuildAbortException(instance_uuid=instance.uuid,

nova/tests/unit/compute/test_compute_mgr.py

@@ -3510,6 +3510,10 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
             exception.ImageUnacceptable(image_id=self.image.get('id'),
                                         reason=""))
 
+    def test_build_and_run_invalid_disk_info_exception(self):
+        self._test_build_and_run_spawn_exceptions(
+            exception.InvalidDiskInfo(reason=""))
+
     def _test_build_and_run_spawn_exceptions(self, exc):
         with contextlib.nested(
                 mock.patch.object(self.compute.driver, 'spawn',

nova/tests/unit/virt/test_images.py

@@ -31,7 +31,7 @@ class QemuTestCase(test.NoDBTestCase):
 
     @mock.patch.object(os.path, 'exists', return_value=True)
     def test_qemu_info_with_errors(self, path_exists):
-        self.assertRaises(processutils.ProcessExecutionError,
+        self.assertRaises(exception.InvalidDiskInfo,
                           images.qemu_img_info,
                           '/fake/path')
 
@@ -43,3 +43,26 @@ class QemuTestCase(test.NoDBTestCase):
         image_info = images.qemu_img_info('/fake/path')
         self.assertTrue(image_info)
         self.assertTrue(str(image_info))
+
+    @mock.patch.object(utils, 'execute',
+                       side_effect=processutils.ProcessExecutionError)
+    def test_convert_image_with_errors(self, mocked_execute):
+        self.assertRaises(exception.ImageUnacceptable,
+                          images.convert_image,
+                          '/path/that/does/not/exist',
+                          '/other/path/that/does/not/exist',
+                          'qcow2',
+                          'raw')
+
+    @mock.patch.object(images, 'convert_image',
+                       side_effect=exception.ImageUnacceptable)
+    @mock.patch.object(images, 'qemu_img_info')
+    @mock.patch.object(images, 'fetch')
+    def test_fetch_to_raw_errors(self, convert_image, qemu_img_info, fetch):
+        qemu_img_info.backing_file = None
+        qemu_img_info.file_format = 'qcow2'
+        qemu_img_info.virtual_size = 20
+        self.assertRaisesRegex(exception.ImageUnacceptable,
+                               'Image href123 is unacceptable.*',
+                               images.fetch_to_raw,
+                               None, 'href123', '/no/path', None, None)

nova/virt/images.py

@@ -21,6 +21,7 @@ Handling of VM disk images.
 
 import os
 
+from oslo_concurrency import processutils
 from oslo_config import cfg
 from oslo_log import log as logging
 from oslo_utils import fileutils
@@ -59,7 +60,13 @@ def qemu_img_info(path, format=None):
     cmd = ('env', 'LC_ALL=C', 'LANG=C', 'qemu-img', 'info', path)
     if format is not None:
         cmd = cmd + ('-f', format)
-    out, err = utils.execute(*cmd)
+    try:
+        out, err = utils.execute(*cmd)
+    except processutils.ProcessExecutionError as exp:
+        msg = (_("qemu-img failed to execute on %(path)s : %(exp)s") %
+                {'path': path, 'exp': exp})
+        raise exception.InvalidDiskInfo(reason=msg)
+
     if not out:
         msg = (_("Failed to run qemu-img info on %(path)s : %(error)s") %
                {'path': path, 'error': err})
@@ -93,7 +100,12 @@ def _convert_image(source, dest, in_format, out_format, run_as_root):
     cmd = ('qemu-img', 'convert', '-O', out_format, source, dest)
     if in_format is not None:
         cmd = cmd + ('-f', in_format)
-    utils.execute(*cmd, run_as_root=run_as_root)
+    try:
+        utils.execute(*cmd, run_as_root=run_as_root)
+    except processutils.ProcessExecutionError as exp:
+        msg = (_("Unable to convert image to %(format)s: %(exp)s") %
+               {'format': out_format, 'exp': exp})
+        raise exception.ImageUnacceptable(image_id=source, reason=msg)
 
 
 def fetch(context, image_href, path, _user_id, _project_id, max_size=0):
@@ -147,7 +159,14 @@ def fetch_to_raw(context, image_href, path, user_id, project_id, max_size=0):
             staged = "%s.converted" % path
             LOG.debug("%s was %s, converting to raw" % (image_href, fmt))
             with fileutils.remove_path_on_error(staged):
-                convert_image(path_tmp, staged, fmt, 'raw')
+                try:
+                    convert_image(path_tmp, staged, fmt, 'raw')
+                except exception.ImageUnacceptable as exp:
+                    # re-raise to include image_href
+                    raise exception.ImageUnacceptable(image_id=image_href,
+                        reason=_("Unable to convert image to raw: %(exp)s")
+                        % {'exp': exp})
+
                 os.unlink(path_tmp)
 
                 data = qemu_img_info(staged)