Account of primary coming up in the middle of a failover

Author: davissp14

pkg/flypg/zombie.go

@@ -79,7 +79,11 @@ func ZombieDiagnosis(myHostname string, total int, inactive int, active int, con
 	// Calculate our references
 	myCount := total - inactive - totalConflicts
 
+	// We have to fence the primary in case the active cluster is in the middle of a failover.
 	if myCount >= quorum {
+		if totalConflicts > 0 {
+			return "", ErrZombieDiagnosisUndecided
+		}
 		return myHostname, nil
 	}
 

pkg/flypg/zombie_test.go

@@ -157,11 +157,11 @@ func TestZombieDiagnosis(t *testing.T) {
 		}
 
 		primary, err := ZombieDiagnosis(hostname, total, inactive, active, conflictMap)
-		if err != nil {
+		if !errors.Is(err, ErrZombieDiagnosisUndecided) {
 			t.Fatal(err)
 		}
 
-		if primary != hostname {
+		if primary != "" {
 			t.Fatalf("expected %s, got %q", hostname, primary)
 		}
 	})