sharder: make gap and overlap warning logs shorter

Previously, when the audit process detected gaps and/or overlaps in a
DB's shard ranges, it would log a warning that included a list of all
impacted shard ranges. The log message can grow long when there are
gaps or overlaps involving many shard ranges: so long that syslog
might raise an OSError (Message too long).

This patch shortens these log warning messages to only include a count
of the number of gaps and/or overlaps. The count may still be useful
to observe how a problem has developed over time. The detailed
information is better accessed using the swift-manage-shard-ranges
repair command.

Change-Id: I055c40395807708de60882f53652d9533a495d09
Signed-off-by: Alistair Coles <alistairncoles@gmail.com>

swift/container/sharder.py

@@ -1296,9 +1296,8 @@ class ContainerSharder(ContainerSharderConf, ContainerReplicator):
             paths_with_gaps = find_paths_with_gaps(shard_ranges)
             if paths_with_gaps:
                 warnings.append(
-                    'missing range(s): %s' %
-                    ' '.join(['%s-%s' % (gap.lower, gap.upper)
-                              for (_, gap, _) in paths_with_gaps]))
+                    'missing range(s): %s (use swift-manage-shard-ranges '
+                    'repair)' % len(paths_with_gaps))
 
         for state in ShardRange.STATES:
             if state == ShardRange.SHRINKING:
@@ -1322,13 +1321,9 @@ class ContainerSharder(ContainerSharderConf, ContainerReplicator):
                 self._increment_stat('audit_root', 'has_overlap')
                 self._update_stat('audit_root', 'num_overlap',
                                   step=len(overlaps))
-                all_overlaps = ', '.join(
-                    [' '.join(['%s-%s' % (sr.lower, sr.upper)
-                               for sr in overlapping_ranges])
-                     for overlapping_ranges in sorted(list(overlaps))])
                 warnings.append(
-                    'overlapping ranges in state %r: %s' %
-                    (ShardRange.STATES[state], all_overlaps))
+                    'overlapping ranges: %s (use swift-manage-shard-ranges '
+                    'repair)' % len(overlaps))
 
         # We've seen a case in production where the roots own_shard_range
         # epoch is reset to None, and state set to ACTIVE (like re-defaulted)

test/unit/container/test_sharder.py

@@ -6110,13 +6110,13 @@ class TestSharder(BaseTestSharder):
         self.assertFalse(sharder.logger.get_lines_for_level('error'))
         mocked.assert_not_called()
 
-        def assert_overlap_warning(line, state_text):
+        def assert_overlap_warning(line):
             self.assertIn('Audit failed for root', line)
             self.assertIn(broker.db_file, line)
             self.assertIn(broker.path, line)
             self.assertIn(
-                'overlapping ranges in state %r: k-t s-y, y-z y-z'
-                % state_text, line)
+                'overlapping ranges: 2 (use swift-manage-shard-ranges repair)',
+                line)
             # check for no duplicates in reversed order
             self.assertNotIn('s-z k-t', line)
 
@@ -6124,7 +6124,7 @@ class TestSharder(BaseTestSharder):
                           'has_overlap': 1, 'num_overlap': 2}
         shard_bounds = (('a', 'j'), ('k', 't'), ('s', 'y'),
                         ('y', 'z'), ('y', 'z'))
-        for state, state_text in ShardRange.STATES.items():
+        for state in ShardRange.STATES:
             if state in (ShardRange.SHRINKING,
                          ShardRange.SHARDED,
                          ShardRange.SHRUNK):
@@ -6137,7 +6137,7 @@ class TestSharder(BaseTestSharder):
                         sharder, '_audit_shard_container') as mocked:
                     sharder._audit_container(broker)
             lines = sharder.logger.get_lines_for_level('warning')
-            assert_overlap_warning(lines[0], state_text)
+            assert_overlap_warning(lines[0])
             self.assertFalse(lines[1:])
             self.assertFalse(sharder.logger.get_lines_for_level('error'))
             self._assert_stats(expected_stats, sharder, 'audit_root')
@@ -6183,7 +6183,9 @@ class TestSharder(BaseTestSharder):
 
         def assert_missing_warning(line):
             self.assertIn('Audit failed for root', line)
-            self.assertIn('missing range(s): -a j-k z-', line)
+            self.assertIn(
+                'missing range(s): 3 (use swift-manage-shard-ranges repair)',
+                line)
             self.assertIn('path: %s, db: %s' % (broker.path, broker.db_file),
                           line)
 
@@ -6200,7 +6202,7 @@ class TestSharder(BaseTestSharder):
                         sharder._audit_container(broker)
                 lines = sharder.logger.get_lines_for_level('warning')
                 assert_missing_warning(lines[0])
-                assert_overlap_warning(lines[0], 'active')
+                assert_overlap_warning(lines[0])
                 self.assertFalse(lines[1:])
                 self.assertFalse(sharder.logger.get_lines_for_level('error'))
                 self._assert_stats(expected_stats, sharder, 'audit_root')