Randomize SOA refresh interval

Change-Id: I4271d428fbb0d81faaa9c06c41d00d9584e0cd90

designate/__init__.py

@@ -54,7 +54,9 @@ cfg.CONF.register_opts([
     cfg.IntOpt('default-ttl', default=3600),
 
     # Default SOA Values
-    cfg.IntOpt('default-soa-refresh', default=3600),
+    cfg.IntOpt('default-soa-refresh-min', default=3500,
+               deprecated_name='default-soa-refresh'),
+    cfg.IntOpt('default-soa-refresh-max', default=3600),
     cfg.IntOpt('default-soa-retry', default=600),
     cfg.IntOpt('default-soa-expire', default=86400),
     cfg.IntOpt('default-soa-minimum', default=3600),

designate/central/service.py

@@ -843,6 +843,20 @@ class Service(service.RPCService, service.Service):
         return self.storage.count_tenants(context)
 
     # Zone Methods
+
+    def _generate_soa_refresh_interval(self):
+        """Generate a random refresh interval to stagger AXFRs across multiple
+        zones and resolvers
+        maximum val: default_soa_refresh_min
+        minimum val: default_soa_refresh_max
+        """
+        assert cfg.CONF.default_soa_refresh_min is not None
+        assert cfg.CONF.default_soa_refresh_max is not None
+        dispersion = (cfg.CONF.default_soa_refresh_max -
+                      cfg.CONF.default_soa_refresh_min) * random.random()
+        refresh_time = cfg.CONF.default_soa_refresh_min + dispersion
+        return int(refresh_time)
+
     @notification('dns.domain.create')
     @notification('dns.zone.create')
     @synchronized_zone(new_zone=True)
@@ -914,6 +928,9 @@ class Service(service.RPCService, service.Service):
         if zone.type == 'SECONDARY' and zone.serial is None:
             zone.serial = 1
 
+        # randomize the zone refresh time
+        zone.refresh = self._generate_soa_refresh_interval()
+
         zone = self._create_zone_in_storage(context, zone)
 
         self.pool_manager_api.create_zone(context, zone)

designate/storage/impl_sqlalchemy/tables.py

@@ -44,6 +44,10 @@ ZONE_TASK_TYPES = ['IMPORT', 'EXPORT']
 
 metadata = MetaData()
 
+# TODO(Federico) some default column values are not needed because we
+# explicitely set the value on record insertion. Having default values could
+# hide bugs.
+
 
 def default_shard(context, id_col):
     return int(context.current_parameters[id_col][0:3], 16)
@@ -96,7 +100,8 @@ zones = Table('zones', metadata,
     Column('transferred_at', DateTime, default=None),
     Column('ttl', Integer, default=CONF.default_ttl, nullable=False),
     Column('serial', Integer, default=timeutils.utcnow_ts, nullable=False),
-    Column('refresh', Integer, default=CONF.default_soa_refresh,
+    # The refresh interval is randomized by _generate_soa_refresh_interval
+    Column('refresh', Integer, default=CONF.default_soa_refresh_min,
            nullable=False),
     Column('retry', Integer, default=CONF.default_soa_retry, nullable=False),
     Column('expire', Integer, default=CONF.default_soa_expire, nullable=False),

designate/tests/test_central/test_service.py

@@ -517,6 +517,11 @@ class CentralServiceTest(CentralTestCase):
         with testtools.ExpectedException(exceptions.OverQuota):
             self.create_zone()
 
+    def test_create_zone_with_refresh_time_dispersion(self):
+        random.seed(42)
+        zone = self.create_zone()
+        self.assertEqual(3563, zone['refresh'])
+
     def test_create_subzone(self):
         # Create the Parent Zone using fixture 0
         parent_zone = self.create_zone(fixture=0)

doc/source/gmr.rst

@@ -4,7 +4,7 @@
  Guru Meditation Reports
 =========================
 
-A Guru Meditation Reports(GMR) is generated by the Designate services when
+A Guru Meditation Report (GMR) is generated by the Designate services when
 service processes receiving SIGUSR2 signal. The report is a general-purpose
 debug report for developers and system admins which contains the current state
 of a running Designate service process.
@@ -309,7 +309,8 @@ GMR Example
       debug = True
       default-soa-expire = 86400
       default-soa-minimum = 3600
-      default-soa-refresh = 3600
+      default-soa-refresh-min = 3500
+      default-soa-refresh-max = 3600
       default-soa-retry = 600
       default-ttl = 3600
       default_log_levels =

releasenotes/notes/soa_refresh_interval_randomization-fcc1d0d63124699b.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - Randomize SOA refresh interval to stagger AXFRs across multiple zones and
+    resolvers.
+    Introduce the new configuration parameters default-soa-refresh-min and
+    default-soa-refresh-max
+deprecations:
+  - default-soa-refresh configuration option