Merge ~blake-rouse/maas:fix-1841807 into maas:master

[Blake Rouse]

Fixes LP: #1841807 - Handle the case where the RPC connection can be lost in a list-boot-images API call.

There is a case where the RPC connection can be lost for multiple reasons during an RPC call to a rack controller. The error path was not handling this case, but was handling other cases. This updates that error path to handle the connection lost case so the API output is consistent and not an improper error or API return code.

[MAAS Lander (maas-lander)]

UNIT TESTS
-b fix-1841807 lp:~blake-rouse/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: SUCCESS
COMMIT: ee25f48bffd2a7f9a71c0631f65c25af47059c0b

review: Approve

[Alberto Donato (ack)]

LGTM, +1

review: Approve

[MAAS Lander (maas-lander)]

LANDING
-b fix-1841807 lp:~blake-rouse/maas/+git/maas into -b master lp:~maas-committers/maas

STATUS: FAILED BUILD
LOG: http://maas-ci-jenkins.internal:8080/job/maas/job/branch-tester/6376/consoleText

diff --git a/src/maasserver/models/node.py b/src/maasserver/models/node.py
index d8fa3d9..c4fe307 100644
--- a/src/maasserver/models/node.py
+++ b/src/maasserver/models/node.py
@@ -256,7 +256,10 @@ from twisted.internet.defer import (
     inlineCallbacks,
     succeed,
 )
-from twisted.internet.error import ConnectionDone
+from twisted.internet.error import (
+    ConnectionClosed,
+    ConnectionDone,
+)
 from twisted.internet.threads import deferToThread
 from twisted.python.failure import Failure
 from twisted.python.threadable import isInIOThread
@@ -6370,7 +6373,7 @@ class RackController(Controller):
                         status = "syncing"
                     else:
                         status = "out-of-sync"
-        except (NoConnectionsAvailable, TimeoutError):
+        except (NoConnectionsAvailable, TimeoutError, ConnectionClosed):
             status = 'unknown'
         return status
 
@@ -6401,7 +6404,7 @@ class RackController(Controller):
             } for (name, arch), subarches in downloaded_boot_images.items()]
             status = self.get_image_sync_status(boot_images)
             return {'images': images, 'connected': True, 'status': status}
-        except (NoConnectionsAvailable, TimeoutError):
+        except (NoConnectionsAvailable, ConnectionClosed, TimeoutError):
             return {'images': [], 'connected': False, 'status': 'unknown'}
 
     def is_import_boot_images_running(self):
diff --git a/src/maasserver/models/tests/test_node.py b/src/maasserver/models/tests/test_node.py
index 66b7374..0765582 100644
--- a/src/maasserver/models/tests/test_node.py
+++ b/src/maasserver/models/tests/test_node.py
@@ -251,7 +251,10 @@ from testtools.matchers import (
     Not,
 )
 from twisted.internet import defer
-from twisted.internet.error import ConnectionDone
+from twisted.internet.error import (
+    ConnectionClosed,
+    ConnectionDone,
+)
 import yaml
 
 
@@ -11727,6 +11730,16 @@ class TestRackController(MAASTransactionServerTestCase):
         self.assertEquals('unknown', images['status'])
         self.assertEquals('unknown', rack_controller.get_image_sync_status())
 
+    def test_list_boot_images_when_connection_closed(self):
+        rack_controller = factory.make_RackController()
+        self.patch(
+            boot_images, 'get_boot_images').side_effect = ConnectionClosed()
+        images = rack_controller.list_boot_images()
+        self.assertEquals(False, images['connected'])
+        self.assertItemsEqual([], images['images'])
+        self.assertEquals('unknown', images['status'])
+        self.assertEquals('unknown', rack_controller.get_image_sync_status())
+
     def test_list_boot_images_region_importing(self):
         rack_controller = factory.make_RackController()
         self.patch(