Add Sentinel RouteBy

CHANGELOG.md

@@ -4,10 +4,14 @@
 
 ## v8 (unreleased)
 
+- Documentation at https://redis.uptrace.dev/
+
 - All commands require `context.Context` as a first argument, e.g. `rdb.Ping(ctx)`. If you are not
   using `context.Context` yet, the simplest option is to define global package variable
   `var ctx = context.TODO()` and use it when `ctx` is required.
 
+- Added `redis.NewFailoverClusterClient` that supports routing read-only commands to a slave node.
+
 - Added `redisext.OpenTemetryHook` that adds
   [Redis OpenTelemetry instrumentation](https://redis.uptrace.dev/tracing/).
 

bench_test.go

@@ -305,31 +305,6 @@ func BenchmarkClusterSetString(b *testing.B) {
 	})
 }
 
-func BenchmarkClusterReloadState(b *testing.B) {
-	if testing.Short() {
-		b.Skip("skipping in short mode")
-	}
-
-	ctx := context.Background()
-	cluster := newClusterScenario()
-	if err := startCluster(ctx, cluster); err != nil {
-		b.Fatal(err)
-	}
-	defer cluster.Close()
-
-	client := cluster.newClusterClient(ctx, redisClusterOptions())
-	defer client.Close()
-
-	b.ResetTimer()
-
-	for i := 0; i < b.N; i++ {
-		err := client.ReloadState(ctx)
-		if err != nil {
-			b.Fatal(err)
-		}
-	}
-}
-
 var clusterSink *redis.ClusterClient
 
 func BenchmarkClusterWithContext(b *testing.B) {

cluster.go

@@ -727,9 +727,8 @@ func (c *ClusterClient) Options() *ClusterOptions {
 
 // ReloadState reloads cluster state. If available it calls ClusterSlots func
 // to get cluster slots information.
-func (c *ClusterClient) ReloadState(ctx context.Context) error {
-	_, err := c.state.Reload(ctx)
-	return err
+func (c *ClusterClient) ReloadState(ctx context.Context) {
+	c.state.LazyReload(ctx)
 }
 
 // Close closes the cluster client, releasing any open resources.
@@ -1638,7 +1637,7 @@ func (c *ClusterClient) cmdNode(
 		return nil, err
 	}
 
-	if c.opt.ReadOnly && cmdInfo != nil && cmdInfo.ReadOnly {
+	if (c.opt.RouteByLatency || c.opt.RouteRandomly) && cmdInfo != nil && cmdInfo.ReadOnly {
 		return c.slotReadOnlyNode(state, slot)
 	}
 	return state.slotMasterNode(slot)

example_test.go

@@ -114,10 +114,7 @@ func ExampleNewClusterClient_manualSetup() {
 
 	// ReloadState reloads cluster state. It calls ClusterSlots func
 	// to get cluster slots information.
-	err := rdb.ReloadState(ctx)
-	if err != nil {
-		panic(err)
-	}
+	rdb.ReloadState(ctx)
 }
 
 func ExampleNewRing() {

sentinel.go

@@ -26,6 +26,13 @@ type FailoverOptions struct {
 	// Sentinel password from "requirepass <password>" (if enabled) in Sentinel configuration
 	SentinelPassword string
 
+	// Allows routing read-only commands to the closest master or slave node.
+	// This option only works with NewFailoverClusterClient.
+	RouteByLatency bool
+	// Allows routing read-only commands to the random master or slave node.
+	// This option only works with NewFailoverClusterClient.
+	RouteRandomly bool
+
 	// Route all commands to slave read-only nodes.
 	SlaveOnly bool
 
@@ -124,6 +131,10 @@ func (opt *FailoverOptions) clusterOptions() *ClusterOptions {
 		Password: opt.Password,
 
 		MaxRedirects: opt.MaxRetries,
+
+		RouteByLatency: opt.RouteByLatency,
+		RouteRandomly:  opt.RouteRandomly,
+
 		MinRetryBackoff: opt.MinRetryBackoff,
 		MaxRetryBackoff: opt.MaxRetryBackoff,
 
@@ -146,6 +157,13 @@ func (opt *FailoverOptions) clusterOptions() *ClusterOptions {
 // for automatic failover. It's safe for concurrent use by multiple
 // goroutines.
 func NewFailoverClient(failoverOpt *FailoverOptions) *Client {
+	if failoverOpt.RouteByLatency {
+		panic("to route commands by latency, use NewFailoverClusterClient")
+	}
+	if failoverOpt.RouteRandomly {
+		panic("to route commands randomly, use NewFailoverClusterClient")
+	}
+
 	sentinelAddrs := make([]string, len(failoverOpt.SentinelAddrs))
 	copy(sentinelAddrs, failoverOpt.SentinelAddrs)
 
@@ -378,7 +396,9 @@ type sentinelFailover struct {
 	opt *FailoverOptions
 
 	sentinelAddrs []string
+
 	onFailover func(ctx context.Context, addr string)
+	onUpdate   func(ctx context.Context)
 
 	mu          sync.RWMutex
 	_masterAddr string
@@ -409,7 +429,7 @@ func (c *sentinelFailover) closeSentinel() error {
 }
 
 func (c *sentinelFailover) RandomSlaveAddr(ctx context.Context) (string, error) {
-	addresses, err := c.slaveAddresses(ctx)
+	addresses, err := c.slaveAddrs(ctx)
 	if err != nil {
 		return "", err
 	}
@@ -464,7 +484,7 @@ func (c *sentinelFailover) MasterAddr(ctx context.Context) (string, error) {
 	return "", errors.New("redis: all sentinels are unreachable")
 }
 
-func (c *sentinelFailover) slaveAddresses(ctx context.Context) ([]string, error) {
+func (c *sentinelFailover) slaveAddrs(ctx context.Context) ([]string, error) {
 	c.mu.RLock()
 	sentinel := c.sentinel
 	c.mu.RUnlock()
@@ -502,7 +522,7 @@ func (c *sentinelFailover) slaveAddresses(ctx context.Context) ([]string, error)
 		c.sentinelAddrs[0], c.sentinelAddrs[i] = c.sentinelAddrs[i], c.sentinelAddrs[0]
 		c.setSentinel(ctx, sentinel)
 
-		addrs := parseSlaveAddresses(slaves)
+		addrs := parseSlaveAddrs(slaves)
 		return addrs, nil
 	}
 
@@ -526,12 +546,11 @@ func (c *sentinelFailover) getSlaveAddrs(ctx context.Context, sentinel *Sentinel
 			c.opt.MasterName, err)
 		return []string{}
 	}
-
-	return parseSlaveAddresses(addrs)
+	return parseSlaveAddrs(addrs)
 }
 
-func parseSlaveAddresses(addrs []interface{}) []string {
-	nodes := []string{}
+func parseSlaveAddrs(addrs []interface{}) []string {
+	nodes := make([]string, 0, len(addrs))
 
 	for _, node := range addrs {
 		ip := ""
@@ -551,12 +570,14 @@ func parseSlaveAddresses(addrs []interface{}) []string {
 			}
 			lastkey = key.(string)
 		}
+
 		for _, flag := range flags {
 			switch flag {
 			case "s_down", "o_down", "disconnected":
 				isDown = true
 			}
 		}
+
 		if !isDown {
 			nodes = append(nodes, net.JoinHostPort(ip, port))
 		}
@@ -584,7 +605,9 @@ func (c *sentinelFailover) trySwitchMaster(ctx context.Context, addr string) {
 
 	internal.Logger.Printf(ctx, "sentinel: new master=%q addr=%q",
 		c.opt.MasterName, addr)
-	go c.onFailover(ctx, addr)
+	if c.onFailover != nil {
+		c.onFailover(ctx, addr)
+	}
 }
 
 func (c *sentinelFailover) setSentinel(ctx context.Context, sentinel *SentinelClient) {
@@ -594,7 +617,7 @@ func (c *sentinelFailover) setSentinel(ctx context.Context, sentinel *SentinelCl
 	c.sentinel = sentinel
 	c.discoverSentinels(ctx)
 
-	c.pubsub = sentinel.Subscribe(ctx, "+switch-master")
+	c.pubsub = sentinel.Subscribe(ctx, "+switch-master", "+slave-reconf-done")
 	go c.listen(c.pubsub)
 }
 
@@ -621,13 +644,13 @@ func (c *sentinelFailover) discoverSentinels(ctx context.Context) {
 }
 
 func (c *sentinelFailover) listen(pubsub *PubSub) {
-	ch := pubsub.Channel()
-	for {
-		msg, ok := <-ch
-		if !ok {
-			break
+	ctx := context.TODO()
+	if c.onUpdate != nil {
+		c.onUpdate(ctx)
 	}
 
+	ch := pubsub.Channel()
+	for msg := range ch {
 		if msg.Channel == "+switch-master" {
 			parts := strings.Split(msg.Payload, " ")
 			if parts[0] != c.opt.MasterName {
@@ -637,6 +660,10 @@ func (c *sentinelFailover) listen(pubsub *PubSub) {
 			addr := net.JoinHostPort(parts[3], parts[4])
 			c.trySwitchMaster(pubsub.getContext(), addr)
 		}
+
+		if c.onUpdate != nil {
+			c.onUpdate(ctx)
+		}
 	}
 }
 
@@ -651,6 +678,8 @@ func contains(slice []string, str string) bool {
 
 //------------------------------------------------------------------------------
 
+// NewFailoverClusterClient returns a client that supports routing read-only commands
+// to a slave node.
 func NewFailoverClusterClient(failoverOpt *FailoverOptions) *ClusterClient {
 	sentinelAddrs := make([]string, len(failoverOpt.SentinelAddrs))
 	copy(sentinelAddrs, failoverOpt.SentinelAddrs)
@@ -671,7 +700,7 @@ func NewFailoverClusterClient(failoverOpt *FailoverOptions) *ClusterClient {
 			Addr: masterAddr,
 		}}
 
-		slaveAddrs, err := failover.slaveAddresses(ctx)
+		slaveAddrs, err := failover.slaveAddrs(ctx)
 		if err != nil {
 			return nil, err
 		}
@@ -693,8 +722,8 @@ func NewFailoverClusterClient(failoverOpt *FailoverOptions) *ClusterClient {
 	}
 
 	c := NewClusterClient(opt)
-	failover.onFailover = func(ctx context.Context, addr string) {
-		_ = c.ReloadState(ctx)
+	failover.onUpdate = func(ctx context.Context) {
+		c.ReloadState(ctx)
 	}
 
 	return c

sentinel_test.go

@@ -113,6 +113,8 @@ var _ = Describe("NewFailoverClusterClient", func() {
 		client = redis.NewFailoverClusterClient(&redis.FailoverOptions{
 			MasterName:    sentinelName,
 			SentinelAddrs: sentinelAddrs,
+
+			RouteRandomly: true,
 		})
 		Expect(client.FlushDB(ctx).Err()).NotTo(HaveOccurred())
 
@@ -152,10 +154,12 @@ var _ = Describe("NewFailoverClusterClient", func() {
 		err := client.Set(ctx, "foo", "master", 0).Err()
 		Expect(err).NotTo(HaveOccurred())
 
+		for i := 0; i < 100; i++ {
 			// Verify.
 			val, err := client.Get(ctx, "foo").Result()
 			Expect(err).NotTo(HaveOccurred())
 			Expect(val).To(Equal("master"))
+		}
 
 		// Create subscription.
 		ch := client.Subscribe(ctx, "foo").Channel()