From 3ccdcfc14c70d0993e3a822590e1091836320549 Mon Sep 17 00:00:00 2001
From: Jeremy Xu <jeremyxu2010@gmail.com>
Date: Sun, 24 Mar 2019 13:46:35 +0800
Subject: [PATCH] support external redis sentinel cluster

Signed-off-by: Jeremy Xu <jeremyxu2010@gmail.com>
---
 configuration/configuration.go                |   3 +
 registry/handlers/app.go                      |  65 ++-
 registry/handlers/app_test.go                 |  57 ++-
 vendor.conf                                   |   1 +
 vendor/github.com/FZambia/sentinel/LICENSE    | 201 +++++++++
 vendor/github.com/FZambia/sentinel/README.md  |  39 ++
 .../github.com/FZambia/sentinel/sentinel.go   | 426 ++++++++++++++++++
 7 files changed, 777 insertions(+), 15 deletions(-)
 create mode 100644 vendor/github.com/FZambia/sentinel/LICENSE
 create mode 100644 vendor/github.com/FZambia/sentinel/README.md
 create mode 100644 vendor/github.com/FZambia/sentinel/sentinel.go

diff --git a/configuration/configuration.go b/configuration/configuration.go
index 34884dd2c..fb1c63879 100644
--- a/configuration/configuration.go
+++ b/configuration/configuration.go
@@ -165,6 +165,9 @@ type Configuration struct {
 		// Addr specifies the the redis instance available to the application.
 		Addr string `yaml:"addr,omitempty"`
 
+		// SentinelMasterSet specifies the the redis sentinel master set name.
+		SentinelMasterSet string `yaml:"sentinelMasterSet,omitempty"`
+
 		// Password string to use when making a connection.
 		Password string `yaml:"password,omitempty"`
 
diff --git a/registry/handlers/app.go b/registry/handlers/app.go
index 057e4e4e8..62fba3fa9 100644
--- a/registry/handlers/app.go
+++ b/registry/handlers/app.go
@@ -3,6 +3,7 @@ package handlers
 import (
 	"context"
 	cryptorand "crypto/rand"
+	"errors"
 	"expvar"
 	"fmt"
 	"math/rand"
@@ -15,6 +16,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/FZambia/sentinel"
+
 	"github.com/docker/distribution"
 	"github.com/docker/distribution/configuration"
 	dcontext "github.com/docker/distribution/context"
@@ -24,7 +27,7 @@ import (
 	"github.com/docker/distribution/notifications"
 	"github.com/docker/distribution/reference"
 	"github.com/docker/distribution/registry/api/errcode"
-	"github.com/docker/distribution/registry/api/v2"
+	v2 "github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/auth"
 	registrymiddleware "github.com/docker/distribution/registry/middleware/registry"
 	repositorymiddleware "github.com/docker/distribution/registry/middleware/repository"
@@ -498,6 +501,44 @@ func (app *App) configureRedis(configuration *configuration.Configuration) {
 		return
 	}
 
+	var getRedisAddr func() (string, error)
+	var testOnBorrow func(c redis.Conn, t time.Time) error
+	if configuration.Redis.SentinelMasterSet != "" {
+		sntnl := &sentinel.Sentinel{
+			Addrs:      strings.Split(configuration.Redis.Addr, ","),
+			MasterName: configuration.Redis.SentinelMasterSet,
+			Dial: func(addr string) (redis.Conn, error) {
+				c, err := redis.DialTimeout("tcp", addr,
+					configuration.Redis.DialTimeout,
+					configuration.Redis.ReadTimeout,
+					configuration.Redis.WriteTimeout)
+				if err != nil {
+					return nil, err
+				}
+				return c, nil
+			},
+		}
+		getRedisAddr = func() (string, error) {
+			return sntnl.MasterAddr()
+		}
+		testOnBorrow = func(c redis.Conn, t time.Time) error {
+			if !sentinel.TestRole(c, "master") {
+				return errors.New("role check failed")
+			}
+			return nil
+		}
+
+	} else {
+		getRedisAddr = func() (string, error) {
+			return configuration.Redis.Addr, nil
+		}
+		testOnBorrow = func(c redis.Conn, t time.Time) error {
+			// TODO(stevvooe): We can probably do something more interesting
+			// here with the health package.
+			_, err := c.Do("PING")
+			return err
+		}
+	}
 	pool := &redis.Pool{
 		Dial: func() (redis.Conn, error) {
 			// TODO(stevvooe): Yet another use case for contextual timing.
@@ -513,8 +554,11 @@ func (app *App) configureRedis(configuration *configuration.Configuration) {
 				}
 			}
 
-			conn, err := redis.DialTimeout("tcp",
-				configuration.Redis.Addr,
+			redisAddr, err := getRedisAddr()
+			if err != nil {
+				return nil, err
+			}
+			conn, err := redis.DialTimeout("tcp", redisAddr,
 				configuration.Redis.DialTimeout,
 				configuration.Redis.ReadTimeout,
 				configuration.Redis.WriteTimeout)
@@ -546,16 +590,11 @@ func (app *App) configureRedis(configuration *configuration.Configuration) {
 			done(nil)
 			return conn, nil
 		},
-		MaxIdle:     configuration.Redis.Pool.MaxIdle,
-		MaxActive:   configuration.Redis.Pool.MaxActive,
-		IdleTimeout: configuration.Redis.Pool.IdleTimeout,
-		TestOnBorrow: func(c redis.Conn, t time.Time) error {
-			// TODO(stevvooe): We can probably do something more interesting
-			// here with the health package.
-			_, err := c.Do("PING")
-			return err
-		},
-		Wait: false, // if a connection is not available, proceed without cache.
+		MaxIdle:      configuration.Redis.Pool.MaxIdle,
+		MaxActive:    configuration.Redis.Pool.MaxActive,
+		IdleTimeout:  configuration.Redis.Pool.IdleTimeout,
+		TestOnBorrow: testOnBorrow,
+		Wait:         false, // if a connection is not available, proceed without cache.
 	}
 
 	app.redis = pool
diff --git a/registry/handlers/app_test.go b/registry/handlers/app_test.go
index f95b441f9..602e98705 100644
--- a/registry/handlers/app_test.go
+++ b/registry/handlers/app_test.go
@@ -11,7 +11,7 @@ import (
 	"github.com/docker/distribution/configuration"
 	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/registry/api/errcode"
-	"github.com/docker/distribution/registry/api/v2"
+	v2 "github.com/docker/distribution/registry/api/v2"
 	"github.com/docker/distribution/registry/auth"
 	_ "github.com/docker/distribution/registry/auth/silly"
 	"github.com/docker/distribution/registry/storage"
@@ -140,7 +140,29 @@ func TestAppDispatcher(t *testing.T) {
 // TestNewApp covers the creation of an application via NewApp with a
 // configuration.
 func TestNewApp(t *testing.T) {
-	ctx := context.Background()
+
+	config := configuration.Configuration{
+		Storage: configuration.Storage{
+			"testdriver": nil,
+			"maintenance": configuration.Parameters{"uploadpurging": map[interface{}]interface{}{
+				"enabled": false,
+			}},
+		},
+		Auth: configuration.Auth{
+			// For now, we simply test that new auth results in a viable
+			// application.
+			"silly": {
+				"realm":   "realm-test",
+				"service": "service-test",
+			},
+		},
+	}
+	runAppWithConfig(t, config)
+}
+
+// TestNewApp covers the creation of an application via NewApp with a
+// configuration(with redis).
+func TestNewAppWithRedis(t *testing.T) {
 	config := configuration.Configuration{
 		Storage: configuration.Storage{
 			"testdriver": nil,
@@ -157,7 +179,38 @@ func TestNewApp(t *testing.T) {
 			},
 		},
 	}
+	config.Redis.Addr = "127.0.0.1:6379"
+	config.Redis.DB = 0
+	runAppWithConfig(t, config)
+}
 
+// TestNewApp covers the creation of an application via NewApp with a
+// configuration(with redis sentinel cluster).
+func TestNewAppWithRedisSentinelCluster(t *testing.T) {
+	config := configuration.Configuration{
+		Storage: configuration.Storage{
+			"testdriver": nil,
+			"maintenance": configuration.Parameters{"uploadpurging": map[interface{}]interface{}{
+				"enabled": false,
+			}},
+		},
+		Auth: configuration.Auth{
+			// For now, we simply test that new auth results in a viable
+			// application.
+			"silly": {
+				"realm":   "realm-test",
+				"service": "service-test",
+			},
+		},
+	}
+	config.Redis.Addr = "192.168.0.11:26379,192.168.0.12:26379"
+	config.Redis.DB = 0
+	config.Redis.SentinelMasterSet = "mymaster"
+	runAppWithConfig(t, config)
+}
+
+func runAppWithConfig(t *testing.T, config configuration.Configuration) {
+	ctx := context.Background()
 	// Mostly, with this test, given a sane configuration, we are simply
 	// ensuring that NewApp doesn't panic. We might want to tweak this
 	// behavior.
diff --git a/vendor.conf b/vendor.conf
index 12f71672f..0baad5561 100644
--- a/vendor.conf
+++ b/vendor.conf
@@ -49,3 +49,4 @@ gopkg.in/yaml.v2 v2.2.1
 rsc.io/letsencrypt e770c10b0f1a64775ae91d240407ce00d1a5bdeb https://github.com/dmcgowan/letsencrypt.git
 github.com/opencontainers/go-digest a6d0ee40d4207ea02364bd3b9e8e77b9159ba1eb
 github.com/opencontainers/image-spec ab7389ef9f50030c9b245bc16b981c7ddf192882
+github.com/FZambia/sentinel 5585739eb4b6478aa30161866ccf9ce0ef5847c7 https://github.com/jeremyxu2010/sentinel.git
diff --git a/vendor/github.com/FZambia/sentinel/LICENSE b/vendor/github.com/FZambia/sentinel/LICENSE
new file mode 100644
index 000000000..8dada3eda
--- /dev/null
+++ b/vendor/github.com/FZambia/sentinel/LICENSE
@@ -0,0 +1,201 @@
+                                 Apache License
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+                        http://www.apache.org/licenses/
+
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diff --git a/vendor/github.com/FZambia/sentinel/README.md b/vendor/github.com/FZambia/sentinel/README.md
new file mode 100644
index 000000000..f544c54ef
--- /dev/null
+++ b/vendor/github.com/FZambia/sentinel/README.md
@@ -0,0 +1,39 @@
+go-sentinel
+===========
+
+Redis Sentinel support for [redigo](https://github.com/gomodule/redigo) library.
+
+Documentation
+-------------
+
+- [API Reference](http://godoc.org/github.com/FZambia/sentinel)
+
+Alternative solution
+--------------------
+
+You can alternatively configure Haproxy between your application and Redis to proxy requests to Redis master instance if you only need HA:
+
+```
+listen redis
+    server redis-01 127.0.0.1:6380 check port 6380 check inter 2s weight 1 inter 2s downinter 5s rise 10 fall 2
+    server redis-02 127.0.0.1:6381 check port 6381 check inter 2s weight 1 inter 2s downinter 5s rise 10 fall 2 backup
+    bind *:6379
+    mode tcp
+    option tcpka
+    option tcplog
+    option tcp-check
+    tcp-check send PING\r\n
+    tcp-check expect string +PONG
+    tcp-check send info\ replication\r\n
+    tcp-check expect string role:master
+    tcp-check send QUIT\r\n
+    tcp-check expect string +OK
+    balance roundrobin
+```
+
+This way you don't need to use this library.
+
+License
+-------
+
+Library is available under the [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0.html). 
diff --git a/vendor/github.com/FZambia/sentinel/sentinel.go b/vendor/github.com/FZambia/sentinel/sentinel.go
new file mode 100644
index 000000000..79209e9f0
--- /dev/null
+++ b/vendor/github.com/FZambia/sentinel/sentinel.go
@@ -0,0 +1,426 @@
+package sentinel
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/garyburd/redigo/redis"
+)
+
+// Sentinel provides a way to add high availability (HA) to Redis Pool using
+// preconfigured addresses of Sentinel servers and name of master which Sentinels
+// monitor. It works with Redis >= 2.8.12 (mostly because of ROLE command that
+// was introduced in that version, it's possible though to support old versions
+// using INFO command).
+//
+// Example of the simplest usage to contact master "mymaster":
+//
+//  func newSentinelPool() *redis.Pool {
+//  	sntnl := &sentinel.Sentinel{
+//  		Addrs:      []string{":26379", ":26380", ":26381"},
+//  		MasterName: "mymaster",
+//  		Dial: func(addr string) (redis.Conn, error) {
+//  			timeout := 500 * time.Millisecond
+//  			c, err := redis.DialTimeout("tcp", addr, timeout, timeout, timeout)
+//  			if err != nil {
+//  				return nil, err
+//  			}
+//  			return c, nil
+//  		},
+//  	}
+//  	return &redis.Pool{
+//  		MaxIdle:     3,
+//  		MaxActive:   64,
+//  		Wait:        true,
+//  		IdleTimeout: 240 * time.Second,
+//  		Dial: func() (redis.Conn, error) {
+//  			masterAddr, err := sntnl.MasterAddr()
+//  			if err != nil {
+//  				return nil, err
+//  			}
+//  			c, err := redis.Dial("tcp", masterAddr)
+//  			if err != nil {
+//  				return nil, err
+//  			}
+//  			return c, nil
+//  		},
+//  		TestOnBorrow: func(c redis.Conn, t time.Time) error {
+//  			if !sentinel.TestRole(c, "master") {
+//  				return errors.New("Role check failed")
+//  			} else {
+//  				return nil
+//  			}
+//  		},
+//  	}
+//  }
+type Sentinel struct {
+	// Addrs is a slice with known Sentinel addresses.
+	Addrs []string
+
+	// MasterName is a name of Redis master Sentinel servers monitor.
+	MasterName string
+
+	// Dial is a user supplied function to connect to Sentinel on given address. This
+	// address will be chosen from Addrs slice.
+	// Note that as per the redis-sentinel client guidelines, a timeout is mandatory
+	// while connecting to Sentinels, and should not be set to 0.
+	Dial func(addr string) (redis.Conn, error)
+
+	// Pool is a user supplied function returning custom connection pool to Sentinel.
+	// This can be useful to tune options if you are not satisfied with what default
+	// Sentinel pool offers. See defaultPool() method for default pool implementation.
+	// In most cases you only need to provide Dial function and let this be nil.
+	Pool func(addr string) *redis.Pool
+
+	mu    sync.RWMutex
+	pools map[string]*redis.Pool
+	addr  string
+}
+
+// NoSentinelsAvailable is returned when all sentinels in the list are exhausted
+// (or none configured), and contains the last error returned by Dial (which
+// may be nil)
+type NoSentinelsAvailable struct {
+	lastError error
+}
+
+func (ns NoSentinelsAvailable) Error() string {
+	if ns.lastError != nil {
+		return fmt.Sprintf("redigo: no sentinels available; last error: %s", ns.lastError.Error())
+	}
+	return fmt.Sprintf("redigo: no sentinels available")
+}
+
+// putToTop puts Sentinel address to the top of address list - this means
+// that all next requests will use Sentinel on this address first.
+//
+// From Sentinel guidelines:
+//
+// The first Sentinel replying to the client request should be put at the
+// start of the list, so that at the next reconnection, we'll try first
+// the Sentinel that was reachable in the previous connection attempt,
+// minimizing latency.
+//
+// Lock must be held by caller.
+func (s *Sentinel) putToTop(addr string) {
+	addrs := s.Addrs
+	if addrs[0] == addr {
+		// Already on top.
+		return
+	}
+	newAddrs := []string{addr}
+	for _, a := range addrs {
+		if a == addr {
+			continue
+		}
+		newAddrs = append(newAddrs, a)
+	}
+	s.Addrs = newAddrs
+}
+
+// putToBottom puts Sentinel address to the bottom of address list.
+// We call this method internally when see that some Sentinel failed to answer
+// on application request so next time we start with another one.
+//
+// Lock must be held by caller.
+func (s *Sentinel) putToBottom(addr string) {
+	addrs := s.Addrs
+	if addrs[len(addrs)-1] == addr {
+		// Already on bottom.
+		return
+	}
+	newAddrs := []string{}
+	for _, a := range addrs {
+		if a == addr {
+			continue
+		}
+		newAddrs = append(newAddrs, a)
+	}
+	newAddrs = append(newAddrs, addr)
+	s.Addrs = newAddrs
+}
+
+// defaultPool returns a connection pool to one Sentinel. This allows
+// us to call concurrent requests to Sentinel using connection Do method.
+func (s *Sentinel) defaultPool(addr string) *redis.Pool {
+	return &redis.Pool{
+		MaxIdle:     3,
+		MaxActive:   10,
+		Wait:        true,
+		IdleTimeout: 240 * time.Second,
+		Dial: func() (redis.Conn, error) {
+			return s.Dial(addr)
+		},
+		TestOnBorrow: func(c redis.Conn, t time.Time) error {
+			_, err := c.Do("PING")
+			return err
+		},
+	}
+}
+
+func (s *Sentinel) get(addr string) redis.Conn {
+	pool := s.poolForAddr(addr)
+	return pool.Get()
+}
+
+func (s *Sentinel) poolForAddr(addr string) *redis.Pool {
+	s.mu.Lock()
+	if s.pools == nil {
+		s.pools = make(map[string]*redis.Pool)
+	}
+	pool, ok := s.pools[addr]
+	if ok {
+		s.mu.Unlock()
+		return pool
+	}
+	s.mu.Unlock()
+	newPool := s.newPool(addr)
+	s.mu.Lock()
+	p, ok := s.pools[addr]
+	if ok {
+		s.mu.Unlock()
+		return p
+	}
+	s.pools[addr] = newPool
+	s.mu.Unlock()
+	return newPool
+}
+
+func (s *Sentinel) newPool(addr string) *redis.Pool {
+	if s.Pool != nil {
+		return s.Pool(addr)
+	}
+	return s.defaultPool(addr)
+}
+
+// close connection pool to Sentinel.
+// Lock must be hold by caller.
+func (s *Sentinel) close() {
+	if s.pools != nil {
+		for _, pool := range s.pools {
+			pool.Close()
+		}
+	}
+	s.pools = nil
+}
+
+func (s *Sentinel) doUntilSuccess(f func(redis.Conn) (interface{}, error)) (interface{}, error) {
+	s.mu.RLock()
+	addrs := s.Addrs
+	s.mu.RUnlock()
+
+	var lastErr error
+
+	for _, addr := range addrs {
+		conn := s.get(addr)
+		reply, err := f(conn)
+		conn.Close()
+		if err != nil {
+			lastErr = err
+			s.mu.Lock()
+			pool, ok := s.pools[addr]
+			if ok {
+				pool.Close()
+				delete(s.pools, addr)
+			}
+			s.putToBottom(addr)
+			s.mu.Unlock()
+			continue
+		}
+		s.putToTop(addr)
+		return reply, nil
+	}
+
+	return nil, NoSentinelsAvailable{lastError: lastErr}
+}
+
+// MasterAddr returns an address of current Redis master instance.
+func (s *Sentinel) MasterAddr() (string, error) {
+	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
+		return queryForMaster(c, s.MasterName)
+	})
+	if err != nil {
+		return "", err
+	}
+	return res.(string), nil
+}
+
+// SlaveAddrs returns a slice with known slave addresses of current master instance.
+func (s *Sentinel) SlaveAddrs() ([]string, error) {
+	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
+		return queryForSlaveAddrs(c, s.MasterName)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return res.([]string), nil
+}
+
+// Slave represents a Redis slave instance which is known by Sentinel.
+type Slave struct {
+	ip    string
+	port  string
+	flags string
+}
+
+// Addr returns an address of slave.
+func (s *Slave) Addr() string {
+	return net.JoinHostPort(s.ip, s.port)
+}
+
+// Available returns if slave is in working state at moment based on information in slave flags.
+func (s *Slave) Available() bool {
+	return !strings.Contains(s.flags, "disconnected") && !strings.Contains(s.flags, "s_down")
+}
+
+// Slaves returns a slice with known slaves of master instance.
+func (s *Sentinel) Slaves() ([]*Slave, error) {
+	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
+		return queryForSlaves(c, s.MasterName)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return res.([]*Slave), nil
+}
+
+// SentinelAddrs returns a slice of known Sentinel addresses Sentinel server aware of.
+func (s *Sentinel) SentinelAddrs() ([]string, error) {
+	res, err := s.doUntilSuccess(func(c redis.Conn) (interface{}, error) {
+		return queryForSentinels(c, s.MasterName)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return res.([]string), nil
+}
+
+// Discover allows to update list of known Sentinel addresses. From docs:
+//
+// A client may update its internal list of Sentinel nodes following this procedure:
+// 1) Obtain a list of other Sentinels for this master using the command SENTINEL sentinels <master-name>.
+// 2) Add every ip:port pair not already existing in our list at the end of the list.
+func (s *Sentinel) Discover() error {
+	addrs, err := s.SentinelAddrs()
+	if err != nil {
+		return err
+	}
+	s.mu.Lock()
+	for _, addr := range addrs {
+		if !stringInSlice(addr, s.Addrs) {
+			s.Addrs = append(s.Addrs, addr)
+		}
+	}
+	s.mu.Unlock()
+	return nil
+}
+
+// Close closes current connection to Sentinel.
+func (s *Sentinel) Close() error {
+	s.mu.Lock()
+	s.close()
+	s.mu.Unlock()
+	return nil
+}
+
+// TestRole wraps GetRole in a test to verify if the role matches an expected
+// role string. If there was any error in querying the supplied connection,
+// the function returns false. Works with Redis >= 2.8.12.
+// It's not goroutine safe, but if you call this method on pooled connections
+// then you are OK.
+func TestRole(c redis.Conn, expectedRole string) bool {
+	role, err := getRole(c)
+	if err != nil || role != expectedRole {
+		return false
+	}
+	return true
+}
+
+// getRole is a convenience function supplied to query an instance (master or
+// slave) for its role. It attempts to use the ROLE command introduced in
+// redis 2.8.12.
+func getRole(c redis.Conn) (string, error) {
+	res, err := c.Do("ROLE")
+	if err != nil {
+		return "", err
+	}
+	rres, ok := res.([]interface{})
+	if ok {
+		return redis.String(rres[0], nil)
+	}
+	return "", errors.New("redigo: can not transform ROLE reply to string")
+}
+
+func queryForMaster(conn redis.Conn, masterName string) (string, error) {
+	res, err := redis.Strings(conn.Do("SENTINEL", "get-master-addr-by-name", masterName))
+	if err != nil {
+		return "", err
+	}
+	if len(res) < 2 {
+		return "", errors.New("redigo: malformed get-master-addr-by-name reply")
+	}
+	masterAddr := net.JoinHostPort(res[0], res[1])
+	return masterAddr, nil
+}
+
+func queryForSlaveAddrs(conn redis.Conn, masterName string) ([]string, error) {
+	slaves, err := queryForSlaves(conn, masterName)
+	if err != nil {
+		return nil, err
+	}
+	slaveAddrs := make([]string, 0)
+	for _, slave := range slaves {
+		slaveAddrs = append(slaveAddrs, slave.Addr())
+	}
+	return slaveAddrs, nil
+}
+
+func queryForSlaves(conn redis.Conn, masterName string) ([]*Slave, error) {
+	res, err := redis.Values(conn.Do("SENTINEL", "slaves", masterName))
+	if err != nil {
+		return nil, err
+	}
+	slaves := make([]*Slave, 0)
+	for _, a := range res {
+		sm, err := redis.StringMap(a, err)
+		if err != nil {
+			return slaves, err
+		}
+		slave := &Slave{
+			ip:    sm["ip"],
+			port:  sm["port"],
+			flags: sm["flags"],
+		}
+		slaves = append(slaves, slave)
+	}
+	return slaves, nil
+}
+
+func queryForSentinels(conn redis.Conn, masterName string) ([]string, error) {
+	res, err := redis.Values(conn.Do("SENTINEL", "sentinels", masterName))
+	if err != nil {
+		return nil, err
+	}
+	sentinels := make([]string, 0)
+	for _, a := range res {
+		sm, err := redis.StringMap(a, err)
+		if err != nil {
+			return sentinels, err
+		}
+		sentinels = append(sentinels, fmt.Sprintf("%s:%s", sm["ip"], sm["port"]))
+	}
+	return sentinels, nil
+}
+
+func stringInSlice(str string, slice []string) bool {
+	for _, s := range slice {
+		if s == str {
+			return true
+		}
+	}
+	return false
+}
