Abstract CitusHandler and decouple it from configuration (#2950)

the main issue was that the configuration for Citus handler and for DCS existed in two places, while ideally AbstractDCS should not know many details about what kind of MPP is in use.

To solve the problem we first dynamically create an object implementing AbstractMPP interfaces, which is a configuration for DCS. Later this object is used to instantiate the class implementing AbstractMPPHandler interface.

This is just a starting point, which does some heavy lifting. As a next steps all kind of variables named after Citus in files different from patroni/postgres/mpp/citus.py should be renamed.

In other words this commit takes over the most complex part of #2940, which was never implemented.

Co-authored-by: zhjwpku <[email protected]>

tests/test_kubernetes.py

@@ -8,9 +8,11 @@ import unittest
 import urllib3
 
 from mock import Mock, PropertyMock, mock_open, patch
+from patroni.dcs import get_dcs
 from patroni.dcs.kubernetes import Cluster, k8s_client, k8s_config, K8sConfig, K8sConnectionFailed, \
     K8sException, K8sObject, Kubernetes, KubernetesError, KubernetesRetriableException, \
     Retry, RetryFailedError, SERVICE_HOST_ENV_NAME, SERVICE_PORT_ENV_NAME
+from patroni.postgresql.mpp import get_mpp
 from threading import Thread
 from . import MockResponse, SleepException
 
@@ -225,11 +227,12 @@ class BaseTestKubernetes(unittest.TestCase):
     @patch.object(k8s_client.CoreV1Api, 'list_namespaced_pod', mock_list_namespaced_pod, create=True)
     @patch.object(k8s_client.CoreV1Api, 'list_namespaced_config_map', mock_list_namespaced_config_map, create=True)
     def setUp(self, config=None):
-        config = config or {}
-        config.update(ttl=30, scope='test', name='p-0', loop_wait=10, group=0,
-                      retry_timeout=10, labels={'f': 'b'}, bypass_api_service=True)
-        self.k = Kubernetes(config)
-        self.k._citus_group = None
+        config = {'ttl': 30, 'scope': 'test', 'name': 'p-0', 'loop_wait': 10, 'retry_timeout': 10,
+                  'kubernetes': {'labels': {'f': 'b'}, 'bypass_api_service': True, **(config or {})},
+                  'citus': {'group': 0, 'database': 'postgres'}}
+        self.k = get_dcs(config)
+        self.assertIsInstance(self.k, Kubernetes)
+        self.k._mpp = get_mpp({})
         self.assertRaises(AttributeError, self.k._pods._build_cache)
         self.k._pods._is_ready = True
         self.assertRaises(TypeError, self.k._kinds._build_cache)
@@ -254,7 +257,7 @@ class TestKubernetesConfigMaps(BaseTestKubernetes):
             self.assertRaises(KubernetesError, self.k.get_cluster)
 
     def test__get_citus_cluster(self):
-        self.k._citus_group = '0'
+        self.k._mpp = get_mpp({'citus': {'group': 0, 'database': 'postgres'}})
         cluster = self.k.get_cluster()
         self.assertIsInstance(cluster, Cluster)
         self.assertIsInstance(cluster.workers[1], Cluster)
@@ -466,7 +469,7 @@ class TestCacheBuilder(BaseTestKubernetes):
     @patch('patroni.dcs.kubernetes.ObjectCache._watch', mock_watch)
     @patch.object(urllib3.HTTPResponse, 'read_chunked')
     def test__build_cache(self, mock_read_chunked):
-        self.k._citus_group = '0'
+        self.k._mpp = get_mpp({'citus': {'group': 0, 'database': 'postgres'}})
         mock_read_chunked.return_value = [json.dumps(
             {'type': 'MODIFIED', 'object': {'metadata': {
                 'name': self.k.config_path, 'resourceVersion': '2', 'annotations': {self.k._CONFIG: 'foo'}}}}