make TestLeaderPriority stable

Signed-off-by: Ryan Leung <[email protected]>

tests/server/member/member_test.go

@@ -161,21 +161,32 @@ func TestLeaderPriority(t *testing.T) {
 
 	re.NotEmpty(cluster.WaitLeader())
 
-	leader1, err := cluster.GetServer("pd1").GetEtcdLeader()
+	leader, err := cluster.GetServer("pd1").GetEtcdLeader()
 	re.NoError(err)
-	server1 := cluster.GetServer(leader1)
-	addr := server1.GetConfig().ClientUrls
+	server := cluster.GetServer(leader)
+	addr := server.GetConfig().ClientUrls
 	// PD leader should sync with etcd leader.
 	testutil.Eventually(re, func() bool {
-		return cluster.GetLeader() == leader1
+		leader, err := cluster.GetServer("pd1").GetEtcdLeader()
+		if err != nil {
+			return false
+		}
+		return cluster.GetLeader() == leader
 	})
 	// Bind a lower priority to current leader.
-	post(t, re, addr+"/pd/api/v1/members/name/"+leader1, `{"leader-priority": -1}`)
-	// Wait etcd leader change.
-	leader2 := waitEtcdLeaderChange(re, server1, leader1)
+	post(t, re, addr+"/pd/api/v1/members/name/"+leader, `{"leader-priority": -1}`)
+
+	oldLeader := leader
 	// PD leader should sync with etcd leader again.
 	testutil.Eventually(re, func() bool {
-		return cluster.GetLeader() == leader2
+		// Wait etcd leader change.
+		newLeader := waitEtcdLeaderChange(re, server, oldLeader)
+		if cluster.GetLeader() == newLeader {
+			return true
+		}
+		// prevent the etcd leader from changing again before pd is elected as leader
+		oldLeader = newLeader
+		return false
 	})
 }