don't print cached dispersion if it's a lie

Change-Id: I551fcaf274876861feb12848749590f220842d68

3 files changed, 28 insertions, 4 deletions

diff --git a/swift/cli/ringbuilder.py b/swift/cli/ringbuilder.py
index 3bf073550..65ad12e51 100755
--- a/swift/cli/ringbuilder.py
+++ b/swift/cli/ringbuilder.py
@@ -248,10 +248,12 @@ swift-ring-builder <builder_file>
             dev_count = len([dev for dev in builder.devs
                              if dev is not None])
             balance = builder.get_balance()
+        dispersion_trailer = '' if builder.dispersion is None else (
+            ', %.02f dispersion' % (builder.dispersion))
         print '%d partitions, %.6f replicas, %d regions, %d zones, ' \
-              '%d devices, %.02f balance, %.02f dispersion' % (
+              '%d devices, %.02f balance%s' % (
                   builder.parts, builder.replicas, regions, zones, dev_count,
-                  balance, builder.dispersion)
+                  balance, dispersion_trailer)
         print 'The minimum number of hours before a partition can be ' \
               'reassigned is %s' % builder.min_part_hours
         print 'The overload factor is %.6f' % builder.overload
@@ -637,7 +639,7 @@ swift-ring-builder <builder_file> rebalance [options]
                   )
             print '-' * 79
             exit(EXIT_ERROR)
-        if not parts:
+        if not (parts or options.force):
             print 'No partitions could be reassigned.'
             print 'Either none need to be or none can be due to ' \
                   'min_part_hours [%s].' % builder.min_part_hours
diff --git a/swift/common/ring/builder.py b/swift/common/ring/builder.py
index 11324ec43..a0d0d5200 100644
--- a/swift/common/ring/builder.py
+++ b/swift/common/ring/builder.py
@@ -147,7 +147,7 @@ class RingBuilder(object):
             self._last_part_moves = builder['_last_part_moves']
             self._last_part_gather_start = builder['_last_part_gather_start']
             self._dispersion_graph = builder.get('_dispersion_graph', {})
-            self.dispersion = builder.get('dispersion', 0.0)
+            self.dispersion = builder.get('dispersion')
             self._remove_devs = builder['_remove_devs']
         self._ring = None
 
diff --git a/test/unit/cli/test_ringbuilder.py b/test/unit/cli/test_ringbuilder.py
index 2fb231f9d..82abeb954 100644
--- a/test/unit/cli/test_ringbuilder.py
+++ b/test/unit/cli/test_ringbuilder.py
@@ -381,6 +381,28 @@ class TestRebalanceCommand(unittest.TestCase):
         out, err = self.run_srb("rebalance")
         self.assertTrue("rebalance/repush" in out)
 
+    def test_cached_dispersion_value(self):
+        self.run_srb("create", 8, 3, 24)
+        self.run_srb("add",
+                     "r1z1-10.1.1.1:2345/sda", 100.0,
+                     "r1z1-10.1.1.1:2345/sdb", 100.0,
+                     "r1z1-10.1.1.1:2345/sdc", 100.0,
+                     "r1z1-10.1.1.1:2345/sdd", 100.0)
+        self.run_srb('rebalance')
+        out, err = self.run_srb()  # list devices
+        self.assertTrue('dispersion' in out)
+        # remove cached dispersion value
+        builder = RingBuilder.load(self.tempfile)
+        builder.dispersion = None
+        builder.save(self.tempfile)
+        # now dispersion output is supressed
+        out, err = self.run_srb()  # list devices
+        self.assertFalse('dispersion' in out)
+        # but will show up after rebalance
+        self.run_srb('rebalance', '-f')
+        out, err = self.run_srb()  # list devices
+        self.assertTrue('dispersion' in out)
+
 
 if __name__ == '__main__':
     unittest.main()