Close connections to unused nodes

cluster.go

@@ -28,18 +28,19 @@ type ClusterOptions struct {
 	// Default is 16.
 	MaxRedirects int
 
-	// Enables read queries for a connection to a Redis Cluster slave node.
+	// Enables read-only commands on slave nodes.
 	ReadOnly bool
-
+	// Allows routing read-only commands to the closest master or slave node.
-	// Enables routing read-only queries to the closest master or slave node.
 	RouteByLatency bool
 
 	// Following options are copied from Options struct.
 
 	OnConnect func(*Conn) error
 
-	MaxRetries int
+	MaxRetries      int
-	Password   string
+	MinRetryBackoff time.Duration
+	MaxRetryBackoff time.Duration
+	Password        string
 
 	DialTimeout  time.Duration
 	ReadTimeout  time.Duration
@@ -62,6 +63,19 @@ func (opt *ClusterOptions) init() {
 	if opt.RouteByLatency {
 		opt.ReadOnly = true
 	}
+
+	switch opt.MinRetryBackoff {
+	case -1:
+		opt.MinRetryBackoff = 0
+	case 0:
+		opt.MinRetryBackoff = 8 * time.Millisecond
+	}
+	switch opt.MaxRetryBackoff {
+	case -1:
+		opt.MaxRetryBackoff = 0
+	case 0:
+		opt.MaxRetryBackoff = 512 * time.Millisecond
+	}
 }
 
 func (opt *ClusterOptions) clientOptions() *Options {
@@ -70,9 +84,11 @@ func (opt *ClusterOptions) clientOptions() *Options {
 	return &Options{
 		OnConnect: opt.OnConnect,
 
-		MaxRetries: opt.MaxRetries,
+		MaxRetries:      opt.MaxRetries,
-		Password:   opt.Password,
+		MinRetryBackoff: opt.MinRetryBackoff,
-		ReadOnly:   opt.ReadOnly,
+		MaxRetryBackoff: opt.MaxRetryBackoff,
+		Password:        opt.Password,
+		ReadOnly:        opt.ReadOnly,
 
 		DialTimeout:  opt.DialTimeout,
 		ReadTimeout:  opt.ReadTimeout,
@@ -91,7 +107,9 @@ func (opt *ClusterOptions) clientOptions() *Options {
 type clusterNode struct {
 	Client  *Client
 	Latency time.Duration
-	loading time.Time
+
+	loading    time.Time
+	generation uint32
 }
 
 func newClusterNode(clOpt *ClusterOptions, addr string) *clusterNode {
@@ -122,6 +140,17 @@ func (n *clusterNode) Loading() bool {
 	return !n.loading.IsZero() && time.Since(n.loading) < time.Minute
 }
 
+func (n *clusterNode) Generation() uint32 {
+	return n.generation
+}
+
+func (n *clusterNode) SetGeneration(gen uint32) {
+	if gen < n.generation {
+		panic("gen < n.generation")
+	}
+	n.generation = gen
+}
+
 //------------------------------------------------------------------------------
 
 type clusterNodes struct {
@@ -131,6 +160,8 @@ type clusterNodes struct {
 	addrs  []string
 	nodes  map[string]*clusterNode
 	closed bool
+
+	generation uint32
 }
 
 func newClusterNodes(opt *ClusterOptions) *clusterNodes {
@@ -161,6 +192,39 @@ func (c *clusterNodes) Close() error {
 	return firstErr
 }
 
+func (c *clusterNodes) NextGeneration() uint32 {
+	c.generation++
+	return c.generation
+}
+
+// GC removes unused nodes.
+func (c *clusterNodes) GC(generation uint32) error {
+	var collected []*clusterNode
+	c.mu.Lock()
+	for i := 0; i < len(c.addrs); {
+		addr := c.addrs[i]
+		node := c.nodes[addr]
+		if node.Generation() >= generation {
+			i++
+			continue
+		}
+
+		c.addrs = append(c.addrs[:i], c.addrs[i+1:]...)
+		delete(c.nodes, addr)
+		collected = append(collected, node)
+	}
+	c.mu.Unlock()
+
+	var firstErr error
+	for _, node := range collected {
+		if err := node.Client.Close(); err != nil && firstErr == nil {
+			firstErr = err
+		}
+	}
+
+	return firstErr
+}
+
 func (c *clusterNodes) All() ([]*clusterNode, error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
@@ -176,7 +240,7 @@ func (c *clusterNodes) All() ([]*clusterNode, error) {
 	return nodes, nil
 }
 
-func (c *clusterNodes) Get(addr string) (*clusterNode, error) {
+func (c *clusterNodes) GetOrCreate(addr string) (*clusterNode, error) {
 	var node *clusterNode
 	var ok bool
 
@@ -223,7 +287,7 @@ func (c *clusterNodes) Random() (*clusterNode, error) {
 	var nodeErr error
 	for i := 0; i <= c.opt.MaxRedirects; i++ {
 		n := rand.Intn(len(addrs))
-		node, err := c.Get(addrs[n])
+		node, err := c.GetOrCreate(addrs[n])
 		if err != nil {
 			return nil, err
 		}
@@ -239,30 +303,45 @@ func (c *clusterNodes) Random() (*clusterNode, error) {
 //------------------------------------------------------------------------------
 
 type clusterState struct {
-	nodes *clusterNodes
+	nodes   *clusterNodes
+	masters []*clusterNode
+	slaves  []*clusterNode
+
 	slots [][]*clusterNode
+
+	generation uint32
 }
 
 func newClusterState(nodes *clusterNodes, slots []ClusterSlot, origin string) (*clusterState, error) {
 	c := clusterState{
-		nodes: nodes,
+		nodes:      nodes,
+		generation: nodes.NextGeneration(),
+
 		slots: make([][]*clusterNode, hashtag.SlotNumber),
 	}
 
 	isLoopbackOrigin := isLoopbackAddr(origin)
 	for _, slot := range slots {
 		var nodes []*clusterNode
-		for _, slotNode := range slot.Nodes {
+		for i, slotNode := range slot.Nodes {
 			addr := slotNode.Addr
 			if !isLoopbackOrigin && isLoopbackAddr(addr) {
 				addr = origin
 			}
 
-			node, err := c.nodes.Get(addr)
+			node, err := c.nodes.GetOrCreate(addr)
 			if err != nil {
 				return nil, err
 			}
+
+			node.SetGeneration(c.generation)
 			nodes = append(nodes, node)
+
+			if i == 0 {
+				c.masters = appendNode(c.masters, node)
+			} else {
+				c.slaves = appendNode(c.slaves, node)
+			}
 		}
 
 		for i := slot.Start; i <= slot.End; i++ {
@@ -348,7 +427,7 @@ type ClusterClient struct {
 	cmdsInfoOnce internal.Once
 	cmdsInfo     map[string]*CommandInfo
 
-	// Reports where slots reloading is in progress.
+	// Reports whether slots reloading is in progress.
 	reloading uint32
 }
 
@@ -365,12 +444,12 @@ func NewClusterClient(opt *ClusterOptions) *ClusterClient {
 
 	// Add initial nodes.
 	for _, addr := range opt.Addrs {
-		_, _ = c.nodes.Get(addr)
+		_, _ = c.nodes.GetOrCreate(addr)
 	}
 
 	// Preload cluster slots.
 	for i := 0; i < 10; i++ {
-		state, err := c.reloadSlots()
+		state, err := c.reloadState()
 		if err == nil {
 			c._state.Store(state)
 			break
@@ -394,7 +473,7 @@ func (c *ClusterClient) state() *clusterState {
 	if v != nil {
 		return v.(*clusterState)
 	}
-	c.lazyReloadSlots()
+	c.lazyReloadState()
 	return nil
 }
 
@@ -476,6 +555,10 @@ func (c *ClusterClient) Process(cmd Cmder) error {
 
 	var ask bool
 	for attempt := 0; attempt <= c.opt.MaxRedirects; attempt++ {
+		if attempt > 0 {
+			time.Sleep(node.Client.retryBackoff(attempt))
+		}
+
 		if ask {
 			pipe := node.Client.Pipeline()
 			pipe.Process(NewCmd("ASKING"))
@@ -487,13 +570,14 @@ func (c *ClusterClient) Process(cmd Cmder) error {
 			err = node.Client.Process(cmd)
 		}
 
-		// If there is no (real) error - we are done.
+		// If there is no error - we are done.
 		if err == nil {
 			return nil
 		}
 
 		// If slave is loading - read from master.
 		if c.opt.ReadOnly && internal.IsLoadingError(err) {
+			// TODO: race
 			node.loading = time.Now()
 			continue
 		}
@@ -516,11 +600,11 @@ func (c *ClusterClient) Process(cmd Cmder) error {
 			if state != nil && slot >= 0 {
 				master, _ := state.slotMasterNode(slot)
 				if moved && (master == nil || master.Client.getAddr() != addr) {
-					c.lazyReloadSlots()
+					c.lazyReloadState()
 				}
 			}
 
-			node, err = c.nodes.Get(addr)
+			node, err = c.nodes.GetOrCreate(addr)
 			if err != nil {
 				cmd.setErr(err)
 				return err
@@ -535,39 +619,6 @@ func (c *ClusterClient) Process(cmd Cmder) error {
 	return cmd.Err()
 }
 
-// ForEachNode concurrently calls the fn on each ever known node in the cluster.
-// It returns the first error if any.
-func (c *ClusterClient) ForEachNode(fn func(client *Client) error) error {
-	nodes, err := c.nodes.All()
-	if err != nil {
-		return err
-	}
-
-	var wg sync.WaitGroup
-	errCh := make(chan error, 1)
-	for _, node := range nodes {
-		wg.Add(1)
-		go func(node *clusterNode) {
-			defer wg.Done()
-			err := fn(node.Client)
-			if err != nil {
-				select {
-				case errCh <- err:
-				default:
-				}
-			}
-		}(node)
-	}
-	wg.Wait()
-
-	select {
-	case err := <-errCh:
-		return err
-	default:
-		return nil
-	}
-}
-
 // ForEachMaster concurrently calls the fn on each master node in the cluster.
 // It returns the first error if any.
 func (c *ClusterClient) ForEachMaster(fn func(client *Client) error) error {
@@ -577,19 +628,8 @@ func (c *ClusterClient) ForEachMaster(fn func(client *Client) error) error {
 	}
 
 	var wg sync.WaitGroup
-	visited := make(map[*clusterNode]struct{})
 	errCh := make(chan error, 1)
-	for _, nodes := range state.slots {
+	for _, master := range state.masters {
-		if len(nodes) == 0 {
-			continue
-		}
-
-		master := nodes[0]
-		if _, ok := visited[master]; ok {
-			continue
-		}
-		visited[master] = struct{}{}
-
 		wg.Add(1)
 		go func(node *clusterNode) {
 			defer wg.Done()
@@ -612,16 +652,88 @@ func (c *ClusterClient) ForEachMaster(fn func(client *Client) error) error {
 	}
 }
 
+// ForEachSlave concurrently calls the fn on each slave node in the cluster.
+// It returns the first error if any.
+func (c *ClusterClient) ForEachSlave(fn func(client *Client) error) error {
+	state := c.state()
+	if state == nil {
+		return errNilClusterState
+	}
+
+	var wg sync.WaitGroup
+	errCh := make(chan error, 1)
+	for _, slave := range state.slaves {
+		wg.Add(1)
+		go func(node *clusterNode) {
+			defer wg.Done()
+			err := fn(node.Client)
+			if err != nil {
+				select {
+				case errCh <- err:
+				default:
+				}
+			}
+		}(slave)
+	}
+	wg.Wait()
+
+	select {
+	case err := <-errCh:
+		return err
+	default:
+		return nil
+	}
+}
+
+// ForEachNode concurrently calls the fn on each known node in the cluster.
+// It returns the first error if any.
+func (c *ClusterClient) ForEachNode(fn func(client *Client) error) error {
+	state := c.state()
+	if state == nil {
+		return errNilClusterState
+	}
+
+	var wg sync.WaitGroup
+	errCh := make(chan error, 1)
+	worker := func(node *clusterNode) {
+		defer wg.Done()
+		err := fn(node.Client)
+		if err != nil {
+			select {
+			case errCh <- err:
+			default:
+			}
+		}
+	}
+
+	for _, node := range state.masters {
+		wg.Add(1)
+		go worker(node)
+	}
+	for _, node := range state.slaves {
+		wg.Add(1)
+		go worker(node)
+	}
+
+	wg.Wait()
+	select {
+	case err := <-errCh:
+		return err
+	default:
+		return nil
+	}
+}
+
 // PoolStats returns accumulated connection pool stats.
 func (c *ClusterClient) PoolStats() *PoolStats {
 	var acc PoolStats
 
-	nodes, err := c.nodes.All()
+	state := c.state()
-	if err != nil {
+	if state == nil {
 		return &acc
 	}
 
-	for _, node := range nodes {
+	for _, node := range state.masters {
 		s := node.Client.connPool.Stats()
 		acc.Requests += s.Requests
 		acc.Hits += s.Hits
@@ -629,33 +741,51 @@ func (c *ClusterClient) PoolStats() *PoolStats {
 		acc.TotalConns += s.TotalConns
 		acc.FreeConns += s.FreeConns
 	}
+
+	for _, node := range state.slaves {
+		s := node.Client.connPool.Stats()
+		acc.Requests += s.Requests
+		acc.Hits += s.Hits
+		acc.Timeouts += s.Timeouts
+		acc.TotalConns += s.TotalConns
+		acc.FreeConns += s.FreeConns
+	}
+
 	return &acc
 }
 
-func (c *ClusterClient) lazyReloadSlots() {
+func (c *ClusterClient) lazyReloadState() {
 	if !atomic.CompareAndSwapUint32(&c.reloading, 0, 1) {
 		return
 	}
 
 	go func() {
-		for i := 0; i < 1000; i++ {
+		defer atomic.StoreUint32(&c.reloading, 0)
-			state, err := c.reloadSlots()
+
+		var state *clusterState
+		for {
+			var err error
+			state, err = c.reloadState()
 			if err == pool.ErrClosed {
-				break
+				return
 			}
-			if err == nil {
+
-				c._state.Store(state)
+			if err != nil {
-				break
+				time.Sleep(time.Millisecond)
+				continue
 			}
-			time.Sleep(time.Millisecond)
+
+			c._state.Store(state)
+			break
 		}
 
 		time.Sleep(3 * time.Second)
-		atomic.StoreUint32(&c.reloading, 0)
+		c.nodes.GC(state.generation)
 	}()
 }
 
-func (c *ClusterClient) reloadSlots() (*clusterState, error) {
+// Not thread-safe.
+func (c *ClusterClient) reloadState() (*clusterState, error) {
 	node, err := c.nodes.Random()
 	if err != nil {
 		return nil, err
@@ -799,9 +929,9 @@ func (c *ClusterClient) pipelineReadCmds(
 func (c *ClusterClient) checkMovedErr(cmd Cmder, failedCmds map[*clusterNode][]Cmder) error {
 	moved, ask, addr := internal.IsMovedError(cmd.Err())
 	if moved {
-		c.lazyReloadSlots()
+		c.lazyReloadState()
 
-		node, err := c.nodes.Get(addr)
+		node, err := c.nodes.GetOrCreate(addr)
 		if err != nil {
 			return err
 		}
@@ -809,7 +939,7 @@ func (c *ClusterClient) checkMovedErr(cmd Cmder, failedCmds map[*clusterNode][]C
 		failedCmds[node] = append(failedCmds[node], cmd)
 	}
 	if ask {
-		node, err := c.nodes.Get(addr)
+		node, err := c.nodes.GetOrCreate(addr)
 		if err != nil {
 			return err
 		}
@@ -1029,3 +1159,12 @@ func isLoopbackAddr(addr string) bool {
 
 	return ip.IsLoopback()
 }
+
+func appendNode(nodes []*clusterNode, node *clusterNode) []*clusterNode {
+	for _, n := range nodes {
+		if n == node {
+			return nodes
+		}
+	}
+	return append(nodes, node)
+}

cluster_test.go

@@ -75,7 +75,7 @@ func startCluster(scenario *clusterScenario) error {
 		scenario.nodeIds[pos] = info[:40]
 	}
 
-	// Meet cluster nodes
+	// Meet cluster nodes.
 	for _, client := range scenario.clients {
 		err := client.ClusterMeet("127.0.0.1", scenario.ports[0]).Err()
 		if err != nil {
@@ -83,7 +83,7 @@ func startCluster(scenario *clusterScenario) error {
 		}
 	}
 
-	// Bootstrap masters
+	// Bootstrap masters.
 	slots := []int{0, 5000, 10000, 16384}
 	for pos, master := range scenario.masters() {
 		err := master.ClusterAddSlotsRange(slots[pos], slots[pos+1]-1).Err()
@@ -92,7 +92,7 @@ func startCluster(scenario *clusterScenario) error {
 		}
 	}
 
-	// Bootstrap slaves
+	// Bootstrap slaves.
 	for idx, slave := range scenario.slaves() {
 		masterId := scenario.nodeIds[idx]
 
@@ -115,7 +115,7 @@ func startCluster(scenario *clusterScenario) error {
 		}
 	}
 
-	// Wait until all nodes have consistent info
+	// Wait until all nodes have consistent info.
 	for _, client := range scenario.clients {
 		err := eventually(func() error {
 			res, err := client.ClusterSlots().Result()
@@ -189,62 +189,6 @@ var _ = Describe("ClusterClient", func() {
 	var client *redis.ClusterClient
 
 	assertClusterClient := func() {
-		It("should CLUSTER SLOTS", func() {
-			res, err := client.ClusterSlots().Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(res).To(HaveLen(3))
-
-			wanted := []redis.ClusterSlot{
-				{0, 4999, []redis.ClusterNode{{"", "127.0.0.1:8220"}, {"", "127.0.0.1:8223"}}},
-				{5000, 9999, []redis.ClusterNode{{"", "127.0.0.1:8221"}, {"", "127.0.0.1:8224"}}},
-				{10000, 16383, []redis.ClusterNode{{"", "127.0.0.1:8222"}, {"", "127.0.0.1:8225"}}},
-			}
-			Expect(assertSlotsEqual(res, wanted)).NotTo(HaveOccurred())
-		})
-
-		It("should CLUSTER NODES", func() {
-			res, err := client.ClusterNodes().Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(len(res)).To(BeNumerically(">", 400))
-		})
-
-		It("should CLUSTER INFO", func() {
-			res, err := client.ClusterInfo().Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(res).To(ContainSubstring("cluster_known_nodes:6"))
-		})
-
-		It("should CLUSTER KEYSLOT", func() {
-			hashSlot, err := client.ClusterKeySlot("somekey").Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(hashSlot).To(Equal(int64(hashtag.Slot("somekey"))))
-		})
-
-		It("should CLUSTER COUNT-FAILURE-REPORTS", func() {
-			n, err := client.ClusterCountFailureReports(cluster.nodeIds[0]).Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(n).To(Equal(int64(0)))
-		})
-
-		It("should CLUSTER COUNTKEYSINSLOT", func() {
-			n, err := client.ClusterCountKeysInSlot(10).Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(n).To(Equal(int64(0)))
-		})
-
-		It("should CLUSTER SAVECONFIG", func() {
-			res, err := client.ClusterSaveConfig().Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(res).To(Equal("OK"))
-		})
-
-		It("should CLUSTER SLAVES", func() {
-			nodesList, err := client.ClusterSlaves(cluster.nodeIds[0]).Result()
-			Expect(err).NotTo(HaveOccurred())
-			Expect(nodesList).Should(ContainElement(ContainSubstring("slave")))
-			Expect(nodesList).Should(HaveLen(1))
-		})
-
 		It("should GET/SET/DEL", func() {
 			val, err := client.Get("A").Result()
 			Expect(err).To(Equal(redis.Nil))
@@ -254,55 +198,24 @@ var _ = Describe("ClusterClient", func() {
 			Expect(err).NotTo(HaveOccurred())
 			Expect(val).To(Equal("OK"))
 
-			val, err = client.Get("A").Result()
+			Eventually(func() string {
-			Expect(err).NotTo(HaveOccurred())
+				return client.Get("A").Val()
-			Expect(val).To(Equal("VALUE"))
+			}).Should(Equal("VALUE"))
 
 			cnt, err := client.Del("A").Result()
 			Expect(err).NotTo(HaveOccurred())
 			Expect(cnt).To(Equal(int64(1)))
 		})
 
-		It("returns pool stats", func() {
-			Expect(client.PoolStats()).To(BeAssignableToTypeOf(&redis.PoolStats{}))
-		})
-
-		It("removes idle connections", func() {
-			stats := client.PoolStats()
-			Expect(stats.TotalConns).NotTo(BeZero())
-			Expect(stats.FreeConns).NotTo(BeZero())
-
-			time.Sleep(2 * time.Second)
-
-			stats = client.PoolStats()
-			Expect(stats.TotalConns).To(BeZero())
-			Expect(stats.FreeConns).To(BeZero())
-		})
-
 		It("follows redirects", func() {
 			Expect(client.Set("A", "VALUE", 0).Err()).NotTo(HaveOccurred())
 
 			slot := hashtag.Slot("A")
-			Expect(client.SwapSlotNodes(slot)).To(Equal([]string{"127.0.0.1:8224", "127.0.0.1:8221"}))
+			client.SwapSlotNodes(slot)
 
-			val, err := client.Get("A").Result()
+			Eventually(func() string {
-			Expect(err).NotTo(HaveOccurred())
+				return client.Get("A").Val()
-			Expect(val).To(Equal("VALUE"))
+			}).Should(Equal("VALUE"))
-		})
-
-		It("returns an error when there are no attempts left", func() {
-			opt := redisClusterOptions()
-			opt.MaxRedirects = -1
-			client := cluster.clusterClient(opt)
-
-			slot := hashtag.Slot("A")
-			Expect(client.SwapSlotNodes(slot)).To(Equal([]string{"127.0.0.1:8224", "127.0.0.1:8221"}))
-
-			err := client.Get("A").Err()
-			Expect(err).To(HaveOccurred())
-			Expect(err.Error()).To(ContainSubstring("MOVED"))
-
-			Expect(client.Close()).NotTo(HaveOccurred())
 		})
 
 		It("distributes keys", func() {
@@ -311,9 +224,14 @@ var _ = Describe("ClusterClient", func() {
 				Expect(err).NotTo(HaveOccurred())
 			}
 
-			wanted := []string{"keys=31", "keys=29", "keys=40"}
+			for _, master := range cluster.masters() {
-			for i, master := range cluster.masters() {
+				Eventually(func() string {
-				Expect(master.Info().Val()).To(ContainSubstring(wanted[i]))
+					return master.Info("keyspace").Val()
+				}, 5*time.Second).Should(Or(
+					ContainSubstring("keys=31"),
+					ContainSubstring("keys=29"),
+					ContainSubstring("keys=40"),
+				))
 			}
 		})
 
@@ -330,9 +248,14 @@ var _ = Describe("ClusterClient", func() {
 				Expect(err).NotTo(HaveOccurred())
 			}
 
-			wanted := []string{"keys=31", "keys=29", "keys=40"}
+			for _, master := range cluster.masters() {
-			for i, master := range cluster.masters() {
+				Eventually(func() string {
-				Expect(master.Info().Val()).To(ContainSubstring(wanted[i]))
+					return master.Info("keyspace").Val()
+				}, 5*time.Second).Should(Or(
+					ContainSubstring("keys=31"),
+					ContainSubstring("keys=29"),
+					ContainSubstring("keys=40"),
+				))
 			}
 		})
 
@@ -447,7 +370,7 @@ var _ = Describe("ClusterClient", func() {
 				})
 			}
 
-			Describe("Pipeline", func() {
+			Describe("with Pipeline", func() {
 				BeforeEach(func() {
 					pipe = client.Pipeline().(*redis.Pipeline)
 				})
@@ -459,7 +382,7 @@ var _ = Describe("ClusterClient", func() {
 				assertPipeline()
 			})
 
-			Describe("TxPipeline", func() {
+			Describe("with TxPipeline", func() {
 				BeforeEach(func() {
 					pipe = client.TxPipeline().(*redis.Pipeline)
 				})
@@ -476,22 +399,70 @@ var _ = Describe("ClusterClient", func() {
 			pubsub := client.Subscribe("mychannel")
 			defer pubsub.Close()
 
-			msgi, err := pubsub.ReceiveTimeout(time.Second)
+			Eventually(func() error {
-			Expect(err).NotTo(HaveOccurred())
+				_, err := client.Publish("mychannel", "hello").Result()
-			subscr := msgi.(*redis.Subscription)
+				if err != nil {
-			Expect(subscr.Kind).To(Equal("subscribe"))
+					return err
-			Expect(subscr.Channel).To(Equal("mychannel"))
+				}
-			Expect(subscr.Count).To(Equal(1))
 
-			n, err := client.Publish("mychannel", "hello").Result()
+				msg, err := pubsub.ReceiveTimeout(time.Second)
-			Expect(err).NotTo(HaveOccurred())
+				if err != nil {
-			Expect(n).To(Equal(int64(1)))
+					return err
+				}
 
-			msgi, err = pubsub.ReceiveTimeout(time.Second)
+				_, ok := msg.(*redis.Message)
-			Expect(err).NotTo(HaveOccurred())
+				if !ok {
-			msg := msgi.(*redis.Message)
+					return fmt.Errorf("got %T, wanted *redis.Message", msg)
-			Expect(msg.Channel).To(Equal("mychannel"))
+				}
-			Expect(msg.Payload).To(Equal("hello"))
+
+				return nil
+			}, 30*time.Second).ShouldNot(HaveOccurred())
+		})
+	}
+
+	Describe("ClusterClient", func() {
+		BeforeEach(func() {
+			opt = redisClusterOptions()
+			client = cluster.clusterClient(opt)
+
+			_ = client.ForEachMaster(func(master *redis.Client) error {
+				return master.FlushDB().Err()
+			})
+		})
+
+		AfterEach(func() {
+			Expect(client.Close()).NotTo(HaveOccurred())
+		})
+
+		It("returns pool stats", func() {
+			Expect(client.PoolStats()).To(BeAssignableToTypeOf(&redis.PoolStats{}))
+		})
+
+		It("removes idle connections", func() {
+			stats := client.PoolStats()
+			Expect(stats.TotalConns).NotTo(BeZero())
+			Expect(stats.FreeConns).NotTo(BeZero())
+
+			time.Sleep(2 * time.Second)
+
+			stats = client.PoolStats()
+			Expect(stats.TotalConns).To(BeZero())
+			Expect(stats.FreeConns).To(BeZero())
+		})
+
+		It("returns an error when there are no attempts left", func() {
+			opt := redisClusterOptions()
+			opt.MaxRedirects = -1
+			client := cluster.clusterClient(opt)
+
+			slot := hashtag.Slot("A")
+			client.SwapSlotNodes(slot)
+
+			err := client.Get("A").Err()
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("MOVED"))
+
+			Expect(client.Close()).NotTo(HaveOccurred())
 		})
 
 		It("calls fn for every master node", func() {
@@ -510,9 +481,67 @@ var _ = Describe("ClusterClient", func() {
 				Expect(keys).To(HaveLen(0))
 			}
 		})
-	}
 
-	Describe("default ClusterClient", func() {
+		It("should CLUSTER SLOTS", func() {
+			res, err := client.ClusterSlots().Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(res).To(HaveLen(3))
+
+			wanted := []redis.ClusterSlot{
+				{0, 4999, []redis.ClusterNode{{"", "127.0.0.1:8220"}, {"", "127.0.0.1:8223"}}},
+				{5000, 9999, []redis.ClusterNode{{"", "127.0.0.1:8221"}, {"", "127.0.0.1:8224"}}},
+				{10000, 16383, []redis.ClusterNode{{"", "127.0.0.1:8222"}, {"", "127.0.0.1:8225"}}},
+			}
+			Expect(assertSlotsEqual(res, wanted)).NotTo(HaveOccurred())
+		})
+
+		It("should CLUSTER NODES", func() {
+			res, err := client.ClusterNodes().Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(len(res)).To(BeNumerically(">", 400))
+		})
+
+		It("should CLUSTER INFO", func() {
+			res, err := client.ClusterInfo().Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(res).To(ContainSubstring("cluster_known_nodes:6"))
+		})
+
+		It("should CLUSTER KEYSLOT", func() {
+			hashSlot, err := client.ClusterKeySlot("somekey").Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(hashSlot).To(Equal(int64(hashtag.Slot("somekey"))))
+		})
+
+		It("should CLUSTER COUNT-FAILURE-REPORTS", func() {
+			n, err := client.ClusterCountFailureReports(cluster.nodeIds[0]).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(n).To(Equal(int64(0)))
+		})
+
+		It("should CLUSTER COUNTKEYSINSLOT", func() {
+			n, err := client.ClusterCountKeysInSlot(10).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(n).To(Equal(int64(0)))
+		})
+
+		It("should CLUSTER SAVECONFIG", func() {
+			res, err := client.ClusterSaveConfig().Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(res).To(Equal("OK"))
+		})
+
+		It("should CLUSTER SLAVES", func() {
+			nodesList, err := client.ClusterSlaves(cluster.nodeIds[0]).Result()
+			Expect(err).NotTo(HaveOccurred())
+			Expect(nodesList).Should(ContainElement(ContainSubstring("slave")))
+			Expect(nodesList).Should(HaveLen(1))
+		})
+
+		assertClusterClient()
+	})
+
+	Describe("ClusterClient failover", func() {
 		BeforeEach(func() {
 			opt = redisClusterOptions()
 			client = cluster.clusterClient(opt)
@@ -520,6 +549,10 @@ var _ = Describe("ClusterClient", func() {
 			_ = client.ForEachMaster(func(master *redis.Client) error {
 				return master.FlushDB().Err()
 			})
+
+			_ = client.ForEachSlave(func(slave *redis.Client) error {
+				return slave.ClusterFailover().Err()
+			})
 		})
 
 		AfterEach(func() {

export_test.go

@@ -28,8 +28,9 @@ func (c *ClusterClient) SlotAddrs(slot int) []string {
 }
 
 // SwapSlot swaps a slot's master/slave address for testing MOVED redirects.
-func (c *ClusterClient) SwapSlotNodes(slot int) []string {
+func (c *ClusterClient) SwapSlotNodes(slot int) {
 	nodes := c.state().slots[slot]
-	nodes[0], nodes[1] = nodes[1], nodes[0]
+	if len(nodes) == 2 {
-	return c.SlotAddrs(slot)
+		nodes[0], nodes[1] = nodes[1], nodes[0]
+	}
 }

internal/internal.go

@@ -5,19 +5,20 @@ import (
 	"time"
 )
 
-const retryBackoff = 8 * time.Millisecond
-
 // Retry backoff with jitter sleep to prevent overloaded conditions during intervals
 // https://www.awsarchitectureblog.com/2015/03/backoff.html
-func RetryBackoff(retry int, maxRetryBackoff time.Duration) time.Duration {
+func RetryBackoff(retry int, minBackoff, maxBackoff time.Duration) time.Duration {
 	if retry < 0 {
 		retry = 0
 	}
 
-	backoff := retryBackoff << uint(retry)
+	backoff := minBackoff << uint(retry)
-	if backoff > maxRetryBackoff {
+	if backoff > maxBackoff || backoff < minBackoff {
-		backoff = maxRetryBackoff
+		backoff = maxBackoff
 	}
 
+	if backoff == 0 {
+		return 0
+	}
 	return time.Duration(rand.Int63n(int64(backoff)))
 }

internal/internal_test.go

@@ -2,15 +2,16 @@ package internal
 
 import (
 	"testing"
-	. "github.com/onsi/gomega"
 	"time"
+
+	. "github.com/onsi/gomega"
 )
 
 func TestRetryBackoff(t *testing.T) {
 	RegisterTestingT(t)
-	
+
-	for i := -1; i<= 8; i++ {
+	for i := -1; i <= 16; i++ {
-		backoff := RetryBackoff(i, 512*time.Millisecond)
+		backoff := RetryBackoff(i, time.Millisecond, 512*time.Millisecond)
 		Expect(backoff >= 0).To(BeTrue())
 		Expect(backoff <= 512*time.Millisecond).To(BeTrue())
 	}

options.go

@@ -37,9 +37,11 @@ type Options struct {
 	// Maximum number of retries before giving up.
 	// Default is to not retry failed commands.
 	MaxRetries int
-
+	// Minimum backoff between each retry.
+	// Default is 8 milliseconds; -1 disables backoff.
+	MinRetryBackoff time.Duration
 	// Maximum backoff between each retry.
-	// Default is 512 seconds; -1 disables backoff.
+	// Default is 512 milliseconds; -1 disables backoff.
 	MaxRetryBackoff time.Duration
 
 	// Dial timeout for establishing new connections.
@@ -118,6 +120,13 @@ func (opt *Options) init() {
 	if opt.IdleCheckFrequency == 0 {
 		opt.IdleCheckFrequency = time.Minute
 	}
+
+	switch opt.MinRetryBackoff {
+	case -1:
+		opt.MinRetryBackoff = 0
+	case 0:
+		opt.MinRetryBackoff = 8 * time.Millisecond
+	}
 	switch opt.MaxRetryBackoff {
 	case -1:
 		opt.MaxRetryBackoff = 0

redis.go

@@ -107,13 +107,6 @@ func (c *baseClient) initConn(cn *pool.Conn) error {
 	return nil
 }
 
-func (c *baseClient) Process(cmd Cmder) error {
-	if c.process != nil {
-		return c.process(cmd)
-	}
-	return c.defaultProcess(cmd)
-}
-
 // WrapProcess replaces the process func. It takes a function createWrapper
 // which is supplied by the user. createWrapper takes the old process func as
 // an input and returns the new wrapper process func. createWrapper should
@@ -122,10 +115,17 @@ func (c *baseClient) WrapProcess(fn func(oldProcess func(cmd Cmder) error) func(
 	c.process = fn(c.defaultProcess)
 }
 
+func (c *baseClient) Process(cmd Cmder) error {
+	if c.process != nil {
+		return c.process(cmd)
+	}
+	return c.defaultProcess(cmd)
+}
+
 func (c *baseClient) defaultProcess(cmd Cmder) error {
-	for i := 0; i <= c.opt.MaxRetries; i++ {
+	for attempt := 0; attempt <= c.opt.MaxRetries; attempt++ {
-		if i > 0 {
+		if attempt > 0 {
-			time.Sleep(internal.RetryBackoff(i, c.opt.MaxRetryBackoff))
+			time.Sleep(c.retryBackoff(attempt))
 		}
 
 		cn, _, err := c.getConn()
@@ -160,6 +160,10 @@ func (c *baseClient) defaultProcess(cmd Cmder) error {
 	return cmd.Err()
 }
 
+func (c *baseClient) retryBackoff(attempt int) time.Duration {
+	return internal.RetryBackoff(attempt, c.opt.MinRetryBackoff, c.opt.MaxRetryBackoff)
+}
+
 func (c *baseClient) cmdTimeout(cmd Cmder) time.Duration {
 	if timeout := cmd.readTimeout(); timeout != nil {
 		return *timeout