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Avoid unnecessary updates of the members ZNode. (#2115)

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When deciding whether the ZNode should be updated we rely on the cached version of the cluster, which is updated only when members ZNodes are deleted/created or the `/status`, `/sync`, `/failover`, `/config`, or `/history` ZNodes are updated.

I.e. after the update of the current member ZNode succeeded the cache becomes stale and all further updates are always performed even if the value didn't change. In order to solve it, we introduce the new attribute in the Zookeeper class and will use it for memorizing the actual value and for later comparison.
This commit is contained in:
Alexander Kukushkin
2021-11-12 15:00:54 +01:00
committed by GitHub
parent fd1e0f1c1b
commit 00d125c512
2 changed files with 10 additions and 5 deletions
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patroni/dcs/zookeeper.py
+9 -5
View File
@@ -105,6 +105,7 @@ class ZooKeeper(AbstractDCS):
self._fetch_cluster = True
self._fetch_status = True
self.__last_member_data = None
self._orig_kazoo_connect = self._client._connection._connect
self._client._connection._connect = self._kazoo_connect
@@ -348,11 +349,11 @@ class ZooKeeper(AbstractDCS):
def touch_member(self, data, permanent=False):
cluster = self.cluster
member = cluster and cluster.get_member(self._name, fallback_to_leader=False)
encoded_data = json.dumps(data, separators=(',', ':')).encode('utf-8')
member_data = self.__last_member_data or member and member.data
if member and (self._client.client_id is not None and member.session != self._client.client_id[0] or
not (deep_compare(member.data.get('tags', {}), data.get('tags', {})) and
member.data.get('version') == data.get('version') and
member.data.get('checkpoint_after_promote') == data.get('checkpoint_after_promote'))):
not (deep_compare(member_data.get('tags', {}), data.get('tags', {})) and
member_data.get('version') == data.get('version') and
member_data.get('checkpoint_after_promote') == data.get('checkpoint_after_promote'))):
try:
self._client.delete_async(self.member_path).get(timeout=1)
except NoNodeError:
@@ -361,13 +362,15 @@ class ZooKeeper(AbstractDCS):
return False
member = None
encoded_data = json.dumps(data, separators=(',', ':')).encode('utf-8')
if member:
if deep_compare(data, member.data):
if deep_compare(data, member_data):
return True
else:
try:
self._client.create_async(self.member_path, encoded_data, makepath=True,
ephemeral=not permanent).get(timeout=1)
self.__last_member_data = data
return True
except Exception as e:
if not isinstance(e, NodeExistsError):
@@ -375,6 +378,7 @@ class ZooKeeper(AbstractDCS):
return False
try:
self._client.set_async(self.member_path, encoded_data).get(timeout=1)
self.__last_member_data = data
return True
except Exception:
logger.exception('touch_member')
tests/test_zookeeper.py
+1
View File
@@ -213,6 +213,7 @@ class TestZooKeeper(unittest.TestCase):
self.zk.touch_member({'retry': 'retry'})
self.zk._fetch_cluster = True
self.zk.get_cluster()
self.zk.touch_member({'retry': 'retry'})
self.zk.touch_member({'conn_url': 'postgres://repuser:rep-pass@localhost:5434/postgres',
'api_url': 'http://127.0.0.1:8009/patroni'})