From 03d9226633759aadbaa79ca09aaa7754ffac7338 Mon Sep 17 00:00:00 2001
From: Polina Bungina <bungina@gmail.com>
Date: Tue, 12 Sep 2023 14:02:17 +0200
Subject: [PATCH] Implement Failover.is_failover/switchover properties

---
 patroni/dcs/__init__.py | 9 ++++++++-
 patroni/ha.py           | 8 ++++----
 patroni/utils.py        | 5 +++--
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/patroni/dcs/__init__.py b/patroni/dcs/__init__.py
index 4cef65ea..a3d4dbdd 100644
--- a/patroni/dcs/__init__.py
+++ b/patroni/dcs/__init__.py
@@ -451,7 +451,7 @@ class Leader(NamedTuple):
 
 
 class Failover(NamedTuple):
-    """Immutable object (namedtuple) representing configuration information required for failover/switchover capability.
+    """Immutable object (namedtuple) which represents failover key.
 
     :ivar version: version of the object.
     :ivar leader: name of the leader. If value isn't empty we treat it as a switchover from the specified node.
@@ -547,6 +547,13 @@ class Failover(NamedTuple):
         """
         return int(bool(self.leader)) + int(bool(self.candidate))
 
+    @property
+    def is_switchover(self) -> bool:
+        return bool(self.leader)
+
+    @property
+    def is_failover(self) -> bool:
+        return not self.is_switchover
 
 class ClusterConfig(NamedTuple):
     """Immutable object (namedtuple) which represents cluster configuration.
diff --git a/patroni/ha.py b/patroni/ha.py
index a3b94db9..387c2230 100644
--- a/patroni/ha.py
+++ b/patroni/ha.py
@@ -234,7 +234,7 @@ class Ha(object):
         """
         if not self.cluster.failover:
             return 'failover'
-        return 'switchover' if self.cluster.failover.leader else 'manual failover'
+        return 'switchover' if self.cluster.failover.is_switchover else 'manual failover'
 
     def load_cluster_from_dcs(self) -> None:
         cluster = self.dcs.get_cluster()
@@ -1044,7 +1044,7 @@ class Ha(object):
             return False
 
         # try to pick some other members for switchover and check that they are healthy
-        if failover.leader:
+        if failover.is_switchover:
             if self.state_handler.name == failover.leader:  # I was the leader
                 # exclude desired member which is unhealthy if it was specified
                 if self.is_failover_possible(exclude_failover_candidate=bool(failover.candidate)):
@@ -1101,7 +1101,7 @@ class Ha(object):
 
         if self.cluster.failover:
             # When doing a switchover in synchronous mode only synchronous nodes and former leader are allowed to race
-            if self.cluster.failover.leader and self.sync_mode_is_active() \
+            if self.cluster.failover.is_switchover and self.sync_mode_is_active() \
                     and not self.cluster.sync.matches(self.state_handler.name, True):
                 return False
             return self.manual_failover_process_no_leader() or False
@@ -2022,7 +2022,7 @@ class Ha(object):
         def is_eligible(node: Member) -> bool:
             # in synchronous mode we allow failover (not switchover!) to async node
             if self.sync_mode_is_active() and not self.cluster.sync.matches(node.name)\
-                    and not (failover and not failover.leader):
+                    and not (failover and failover.is_failover):
                 return False
             # Don't spend time on "nofailover" nodes checking.
             # We also don't need nodes which we can't query with the api in the list.
diff --git a/patroni/utils.py b/patroni/utils.py
index 881a2245..4c816bbf 100644
--- a/patroni/utils.py
+++ b/patroni/utils.py
@@ -839,8 +839,9 @@ def cluster_as_json(cluster: 'Cluster', global_config: Optional['GlobalConfig']
         ret['pause'] = True
     if cluster.failover and cluster.failover.scheduled_at:
         ret['scheduled_switchover'] = {'at': cluster.failover.scheduled_at.isoformat()}
-        if cluster.failover.leader:
-            ret['scheduled_switchover']['from'] = cluster.failover.leader
+        if TYPE_CHECKING:  # pragma: no cover
+            assert cluster.failover.leader
+        ret['scheduled_switchover']['from'] = cluster.failover.leader
         if cluster.failover.candidate:
             ret['scheduled_switchover']['to'] = cluster.failover.candidate
     return ret