Use Rendezvous in Ring. Thanks @rafaeleyng for initial idea and implementation

.prettierrc

@@ -0,0 +1,4 @@
+semi: false
+singleQuote: true
+proseWrap: always
+printWidth: 80

CHANGELOG.md

@@ -2,37 +2,63 @@
 
 ## v8 (unreleased)
 
-- All commands accept `context.Context` as first argument.
+- 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 package variable `var ctx = context.TODO()` and use it
+  when `ctx` is expected.
+- Ring uses Rendezvous Hashing by default which provides better distribution.
+  This means that existing keys must be moved to a new location or key will be
+  inaccessible / lost. To use old hashing scheme:
+
+```go
+import "github.com/golang/groupcache/consistenthash"
+
+ring := redis.NewRing(&redis.RingOptions{
+    NewConsistentHash: func() {
+        return consistenthash.New(100, crc32.ChecksumIEEE)
+    },
+})
+```
+
 - Basic support for OpenTelemetry instrumentation.
 
 ## v7.3
 
-- New option `Options.Username` which causes client to use `AuthACL`. Be aware if your connection URL contains username.
+- New option `Options.Username` which causes client to use `AuthACL`. Be aware
+  if your connection URL contains username.
 
 ## v7.2
 
-- Existing `HMSet` is renamed to `HSet` and old deprecated `HMSet` is restored for Redis 3 users.
+- Existing `HMSet` is renamed to `HSet` and old deprecated `HMSet` is restored
+  for Redis 3 users.
 
 ## v7.1
 
-- Existing `Cmd.String` is renamed to `Cmd.Text`. New `Cmd.String` implements `fmt.Stringer` interface.
+- Existing `Cmd.String` is renamed to `Cmd.Text`. New `Cmd.String` implements
+  `fmt.Stringer` interface.
 
 ## v7
 
-- _Important_. Tx.Pipeline now returns a non-transactional pipeline. Use Tx.TxPipeline for a transactional pipeline.
+- _Important_. Tx.Pipeline now returns a non-transactional pipeline. Use
-- WrapProcess is replaced with more convenient AddHook that has access to context.Context.
+  Tx.TxPipeline for a transactional pipeline.
+- WrapProcess is replaced with more convenient AddHook that has access to
+  context.Context.
 - WithContext now can not be used to create a shallow copy of the client.
 - New methods ProcessContext, DoContext, and ExecContext.
 - Client respects Context.Deadline when setting net.Conn deadline.
-- Client listens on Context.Done while waiting for a connection from the pool and returns an error when context context is cancelled.
+- Client listens on Context.Done while waiting for a connection from the pool
-- Add PubSub.ChannelWithSubscriptions that sends `*Subscription` in addition to `*Message` to allow detecting reconnections.
+  and returns an error when context context is cancelled.
-- `time.Time` is now marshalled in RFC3339 format. `rdb.Get("foo").Time()` helper is added to parse the time.
+- Add PubSub.ChannelWithSubscriptions that sends `*Subscription` in addition to
+  `*Message` to allow detecting reconnections.
+- `time.Time` is now marshalled in RFC3339 format. `rdb.Get("foo").Time()`
+  helper is added to parse the time.
 - `SetLimiter` is removed and added `Options.Limiter` instead.
 - `HMSet` is deprecated as of Redis v4.
 
 ## v6.15
 
-- Cluster and Ring pipelines process commands for each node in its own goroutine.
+- Cluster and Ring pipelines process commands for each node in its own
+  goroutine.
 
 ## 6.14
 
@@ -40,16 +66,23 @@
 - Added Options.MaxConnAge.
 - PoolStats.FreeConns is renamed to PoolStats.IdleConns.
 - Add Client.Do to simplify creating custom commands.
-- Add Cmd.String, Cmd.Int, Cmd.Int64, Cmd.Uint64, Cmd.Float64, and Cmd.Bool helpers.
+- Add Cmd.String, Cmd.Int, Cmd.Int64, Cmd.Uint64, Cmd.Float64, and Cmd.Bool
+  helpers.
 - Lower memory usage.
 
 ## v6.13
 
-- Ring got new options called `HashReplicas` and `Hash`. It is recommended to set `HashReplicas = 1000` for better keys distribution between shards.
+- Ring got new options called `HashReplicas` and `Hash`. It is recommended to
-- Cluster client was optimized to use much less memory when reloading cluster state.
+  set `HashReplicas = 1000` for better keys distribution between shards.
-- PubSub.ReceiveMessage is re-worked to not use ReceiveTimeout so it does not lose data when timeout occurres. In most cases it is recommended to use PubSub.Channel instead.
+- Cluster client was optimized to use much less memory when reloading cluster
+  state.
+- PubSub.ReceiveMessage is re-worked to not use ReceiveTimeout so it does not
+  lose data when timeout occurres. In most cases it is recommended to use
+  PubSub.Channel instead.
 - Dialer.KeepAlive is set to 5 minutes by default.
 
 ## v6.12
 
-- ClusterClient got new option called `ClusterSlots` which allows to build cluster of normal Redis Servers that don't have cluster mode enabled. See https://godoc.org/github.com/go-redis/redis#example-NewClusterClient--ManualSetup
+- ClusterClient got new option called `ClusterSlots` which allows to build
+  cluster of normal Redis Servers that don't have cluster mode enabled. See
+  https://godoc.org/github.com/go-redis/redis#example-NewClusterClient--ManualSetup

go.mod

@@ -1,6 +1,8 @@
 module github.com/go-redis/redis/v8
 
 require (
+	github.com/cespare/xxhash v1.1.0
+	github.com/dgryski/go-rendezvous v0.0.0-20180401054734-3692eb46c031
 	github.com/onsi/ginkgo v1.10.1
 	github.com/onsi/gomega v1.7.0
 	go.opentelemetry.io/otel v0.5.0

go.sum

@@ -2,14 +2,19 @@ cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMT
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/DataDog/sketches-go v0.0.0-20190923095040-43f19ad77ff7 h1:qELHH0AWCvf98Yf+CNIJx9vOZOfHFDDzgDRYsnNk/vs=
 github.com/DataDog/sketches-go v0.0.0-20190923095040-43f19ad77ff7/go.mod h1:Q5DbzQ+3AkgGwymQO7aZFNP7ns2lZKGtvRBzRXfdi60=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/benbjohnson/clock v1.0.0 h1:78Jk/r6m4wCi6sndMpty7A//t4dw/RW5fV4ZgDVfX1w=
 github.com/benbjohnson/clock v1.0.0/go.mod h1:bGMdMPoPVvcYyt1gHDf4J2KE153Yf9BuiUKYMaxlTDM=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
+github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dgryski/go-rendezvous v0.0.0-20180401054734-3692eb46c031 h1:GqrUYGzmGuc00lpc+K0wwrqshfkKLwgYFJiCyOZFMVE=
+github.com/dgryski/go-rendezvous v0.0.0-20180401054734-3692eb46c031/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.1-0.20191026205805-5f8ba28d4473/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
@@ -45,6 +50,7 @@ github.com/opentracing/opentracing-go v1.1.1-0.20190913142402-a7454ce5950e/go.mo
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=

internal/consistenthash/consistenthash.go

@@ -1,81 +0,0 @@
-/*
-Copyright 2013 Google Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-     http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-// Package consistenthash provides an implementation of a ring hash.
-package consistenthash
-
-import (
-	"hash/crc32"
-	"sort"
-	"strconv"
-)
-
-type Hash func(data []byte) uint32
-
-type Map struct {
-	hash     Hash
-	replicas int
-	keys     []int // Sorted
-	hashMap  map[int]string
-}
-
-func New(replicas int, fn Hash) *Map {
-	m := &Map{
-		replicas: replicas,
-		hash:     fn,
-		hashMap:  make(map[int]string),
-	}
-	if m.hash == nil {
-		m.hash = crc32.ChecksumIEEE
-	}
-	return m
-}
-
-// Returns true if there are no items available.
-func (m *Map) IsEmpty() bool {
-	return len(m.keys) == 0
-}
-
-// Adds some keys to the hash.
-func (m *Map) Add(keys ...string) {
-	for _, key := range keys {
-		for i := 0; i < m.replicas; i++ {
-			hash := int(m.hash([]byte(strconv.Itoa(i) + key)))
-			m.keys = append(m.keys, hash)
-			m.hashMap[hash] = key
-		}
-	}
-	sort.Ints(m.keys)
-}
-
-// Gets the closest item in the hash to the provided key.
-func (m *Map) Get(key string) string {
-	if m.IsEmpty() {
-		return ""
-	}
-
-	hash := int(m.hash([]byte(key)))
-
-	// Binary search for appropriate replica.
-	idx := sort.Search(len(m.keys), func(i int) bool { return m.keys[i] >= hash })
-
-	// Means we have cycled back to the first replica.
-	if idx == len(m.keys) {
-		idx = 0
-	}
-
-	return m.hashMap[m.keys[idx]]
-}

internal/consistenthash/consistenthash_test.go

@@ -1,110 +0,0 @@
-/*
-Copyright 2013 Google Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-     http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package consistenthash
-
-import (
-	"fmt"
-	"strconv"
-	"testing"
-)
-
-func TestHashing(t *testing.T) {
-
-	// Override the hash function to return easier to reason about values. Assumes
-	// the keys can be converted to an integer.
-	hash := New(3, func(key []byte) uint32 {
-		i, err := strconv.Atoi(string(key))
-		if err != nil {
-			panic(err)
-		}
-		return uint32(i)
-	})
-
-	// Given the above hash function, this will give replicas with "hashes":
-	// 2, 4, 6, 12, 14, 16, 22, 24, 26
-	hash.Add("6", "4", "2")
-
-	testCases := map[string]string{
-		"2":  "2",
-		"11": "2",
-		"23": "4",
-		"27": "2",
-	}
-
-	for k, v := range testCases {
-		if hash.Get(k) != v {
-			t.Errorf("Asking for %s, should have yielded %s", k, v)
-		}
-	}
-
-	// Adds 8, 18, 28
-	hash.Add("8")
-
-	// 27 should now map to 8.
-	testCases["27"] = "8"
-
-	for k, v := range testCases {
-		if hash.Get(k) != v {
-			t.Errorf("Asking for %s, should have yielded %s", k, v)
-		}
-	}
-
-}
-
-func TestConsistency(t *testing.T) {
-	hash1 := New(1, nil)
-	hash2 := New(1, nil)
-
-	hash1.Add("Bill", "Bob", "Bonny")
-	hash2.Add("Bob", "Bonny", "Bill")
-
-	if hash1.Get("Ben") != hash2.Get("Ben") {
-		t.Errorf("Fetching 'Ben' from both hashes should be the same")
-	}
-
-	hash2.Add("Becky", "Ben", "Bobby")
-
-	if hash1.Get("Ben") != hash2.Get("Ben") ||
-		hash1.Get("Bob") != hash2.Get("Bob") ||
-		hash1.Get("Bonny") != hash2.Get("Bonny") {
-		t.Errorf("Direct matches should always return the same entry")
-	}
-
-}
-
-func BenchmarkGet8(b *testing.B)   { benchmarkGet(b, 8) }
-func BenchmarkGet32(b *testing.B)  { benchmarkGet(b, 32) }
-func BenchmarkGet128(b *testing.B) { benchmarkGet(b, 128) }
-func BenchmarkGet512(b *testing.B) { benchmarkGet(b, 512) }
-
-func benchmarkGet(b *testing.B, shards int) {
-
-	hash := New(50, nil)
-
-	var buckets []string
-	for i := 0; i < shards; i++ {
-		buckets = append(buckets, fmt.Sprintf("shard-%d", i))
-	}
-
-	hash.Add(buckets...)
-
-	b.ResetTimer()
-
-	for i := 0; i < b.N; i++ {
-		hash.Get(buckets[i&(shards-1)])
-	}
-}

ring.go

@@ -10,55 +10,61 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/cespare/xxhash"
+	"github.com/dgryski/go-rendezvous"
+
 	"github.com/go-redis/redis/v8/internal"
-	"github.com/go-redis/redis/v8/internal/consistenthash"
 	"github.com/go-redis/redis/v8/internal/hashtag"
 	"github.com/go-redis/redis/v8/internal/pool"
 )
 
-// Hash is type of hash function used in consistent hash.
-type Hash consistenthash.Hash
-
 var errRingShardsDown = errors.New("redis: all ring shards are down")
 
+//------------------------------------------------------------------------------
+
+type ConsistentHash interface {
+	Get(string) string
+}
+
+type rendezvousWrapper struct {
+	*rendezvous.Rendezvous
+}
+
+func (w rendezvousWrapper) Get(key string) string {
+	return w.Lookup(key)
+}
+
+func newRendezvous(shards []string) ConsistentHash {
+	return rendezvousWrapper{rendezvous.New(shards, xxhash.Sum64String)}
+}
+
+//------------------------------------------------------------------------------
+
 // RingOptions are used to configure a ring client and should be
 // passed to NewRing.
 type RingOptions struct {
 	// Map of name => host:port addresses of ring shards.
 	Addrs map[string]string
 
+	// NewClient creates a shard client with provided name and options.
+	NewClient func(name string, opt *Options) *Client
+
 	// Frequency of PING commands sent to check shards availability.
 	// Shard is considered down after 3 subsequent failed checks.
 	HeartbeatFrequency time.Duration
 
-	// Hash function used in consistent hash.
+	// NewConsistentHash returns a consistent hash that is used
-	// Default is crc32.ChecksumIEEE.
+	// to distribute keys across the shards.
-	Hash Hash
-
-	// Number of replicas in consistent hash.
-	// Default is 100 replicas.
 	//
-	// Higher number of replicas will provide less deviation, that is keys will be
+	// See https://medium.com/@dgryski/consistent-hashing-algorithmic-tradeoffs-ef6b8e2fcae8
-	// distributed to nodes more evenly.
+	// for consistent hashing algorithmic tradeoffs.
-	//
+	NewConsistentHash func(shards []string) ConsistentHash
-	// Following is deviation for common nreplicas:
-	//  --------------------------------------------------------
-	//  | nreplicas | standard error | 99% confidence interval |
-	//  |     10    |     0.3152     |      (0.37, 1.98)       |
-	//  |    100    |     0.0997     |      (0.76, 1.28)       |
-	//  |   1000    |     0.0316     |      (0.92, 1.09)       |
-	//  --------------------------------------------------------
-	//
-	//  See https://arxiv.org/abs/1406.2294 for reference
-	HashReplicas int
-
-	// NewClient creates a shard client with provided name and options.
-	NewClient func(name string, opt *Options) *Client
 
 	// Following options are copied from Options struct.
 
 	OnConnect func(*Conn) error
 
+	Username string
 	DB       int
 	Password string
 
@@ -79,12 +85,18 @@ type RingOptions struct {
 }
 
 func (opt *RingOptions) init() {
+	if opt.NewClient == nil {
+		opt.NewClient = func(name string, opt *Options) *Client {
+			return NewClient(opt)
+		}
+	}
+
 	if opt.HeartbeatFrequency == 0 {
 		opt.HeartbeatFrequency = 500 * time.Millisecond
 	}
 
-	if opt.HashReplicas == 0 {
+	if opt.NewConsistentHash == nil {
-		opt.HashReplicas = 100
+		opt.NewConsistentHash = newRendezvous
 	}
 
 	switch opt.MinRetryBackoff {
@@ -127,6 +139,15 @@ type ringShard struct {
 	down   int32
 }
 
+func newRingShard(opt *RingOptions, name, addr string) *ringShard {
+	clopt := opt.clientOptions()
+	clopt.Addr = addr
+
+	return &ringShard{
+		Client: opt.NewClient(name, clopt),
+	}
+}
+
 func (shard *ringShard) String() string {
 	var state string
 	if shard.IsUp() {
@@ -167,41 +188,59 @@ func (shard *ringShard) Vote(up bool) bool {
 type ringShards struct {
 	opt *RingOptions
 
-	mu     sync.RWMutex
+	mu       sync.RWMutex
-	hash   *consistenthash.Map
+	hash     ConsistentHash
-	shards map[string]*ringShard // read only
+	shards   map[string]*ringShard // read only
-	list   []*ringShard          // read only
+	list     []*ringShard          // read only
-	len    int
+	numShard int
-	closed bool
+	closed   bool
 }
 
 func newRingShards(opt *RingOptions) *ringShards {
-	return &ringShards{
+	shards := make(map[string]*ringShard, len(opt.Addrs))
+	list := make([]*ringShard, 0, len(shards))
+
+	for name, addr := range opt.Addrs {
+		shard := newRingShard(opt, name, addr)
+		shards[name] = shard
+
+		list = append(list, shard)
+	}
+
+	c := &ringShards{
 		opt: opt,
 
-		hash:   newConsistentHash(opt),
+		shards: shards,
-		shards: make(map[string]*ringShard),
+		list:   list,
 	}
-}
+	c.rebalance()
 
-func (c *ringShards) Add(name string, cl *Client) {
+	return c
-	shard := &ringShard{Client: cl}
-	c.hash.Add(name)
-	c.shards[name] = shard
-	c.list = append(c.list, shard)
 }
 
 func (c *ringShards) List() []*ringShard {
+	var list []*ringShard
+
 	c.mu.RLock()
-	list := c.list
+	if !c.closed {
+		list = c.list
+	}
 	c.mu.RUnlock()
+
 	return list
 }
 
 func (c *ringShards) Hash(key string) string {
+	key = hashtag.Key(key)
+
+	var hash string
+
 	c.mu.RLock()
-	hash := c.hash.Get(key)
+	if c.numShard > 0 {
+		hash = c.hash.Get(key)
+	}
 	c.mu.RUnlock()
+
 	return hash
 }
 
@@ -215,6 +254,11 @@ func (c *ringShards) GetByKey(key string) (*ringShard, error) {
 		return nil, pool.ErrClosed
 	}
 
+	if c.numShard == 0 {
+		c.mu.RUnlock()
+		return nil, errRingShardsDown
+	}
+
 	hash := c.hash.Get(key)
 	if hash == "" {
 		c.mu.RUnlock()
@@ -227,13 +271,13 @@ func (c *ringShards) GetByKey(key string) (*ringShard, error) {
 	return shard, nil
 }
 
-func (c *ringShards) GetByHash(name string) (*ringShard, error) {
+func (c *ringShards) GetByName(shardName string) (*ringShard, error) {
-	if name == "" {
+	if shardName == "" {
 		return c.Random()
 	}
 
 	c.mu.RLock()
-	shard := c.shards[name]
+	shard := c.shards[shardName]
 	c.mu.RUnlock()
 	return shard, nil
 }
@@ -247,23 +291,14 @@ func (c *ringShards) Heartbeat(frequency time.Duration) {
 	ticker := time.NewTicker(frequency)
 	defer ticker.Stop()
 
-	ctx := context.TODO()
+	ctx := context.Background()
 	for range ticker.C {
 		var rebalance bool
 
-		c.mu.RLock()
+		for _, shard := range c.List() {
-
-		if c.closed {
-			c.mu.RUnlock()
-			break
-		}
-
-		shards := c.list
-		c.mu.RUnlock()
-
-		for _, shard := range shards {
 			err := shard.Client.Ping(ctx).Err()
-			if shard.Vote(err == nil || err == pool.ErrPoolTimeout) {
+			isUp := err == nil || err == pool.ErrPoolTimeout
+			if shard.Vote(isUp) {
 				internal.Logger.Printf("ring shard state changed: %s", shard)
 				rebalance = true
 			}
@@ -281,24 +316,25 @@ func (c *ringShards) rebalance() {
 	shards := c.shards
 	c.mu.RUnlock()
 
-	hash := newConsistentHash(c.opt)
+	liveShards := make([]string, 0, len(shards))
-	var shardsNum int
+
 	for name, shard := range shards {
 		if shard.IsUp() {
-			hash.Add(name)
+			liveShards = append(liveShards, name)
-			shardsNum++
 		}
 	}
 
+	hash := c.opt.NewConsistentHash(liveShards)
+
 	c.mu.Lock()
 	c.hash = hash
-	c.len = shardsNum
+	c.numShard = len(liveShards)
 	c.mu.Unlock()
 }
 
 func (c *ringShards) Len() int {
 	c.mu.RLock()
-	l := c.len
+	l := c.numShard
 	c.mu.RUnlock()
 	return l
 }
@@ -364,29 +400,15 @@ func NewRing(opt *RingOptions) *Ring {
 		},
 		ctx: context.Background(),
 	}
+
 	ring.cmdsInfoCache = newCmdsInfoCache(ring.cmdsInfo)
 	ring.cmdable = ring.Process
 
-	for name, addr := range opt.Addrs {
-		shard := newRingShard(opt, name, addr)
-		ring.shards.Add(name, shard)
-	}
-
 	go ring.shards.Heartbeat(opt.HeartbeatFrequency)
 
 	return &ring
 }
 
-func newRingShard(opt *RingOptions, name, addr string) *Client {
-	clopt := opt.clientOptions()
-	clopt.Addr = addr
-
-	if opt.NewClient != nil {
-		return opt.NewClient(name, clopt)
-	}
-	return NewClient(clopt)
-}
-
 func (c *Ring) Context() context.Context {
 	return c.ctx
 }
@@ -623,7 +645,7 @@ func (c *Ring) generalProcessPipeline(
 		cmdInfo := c.cmdInfo(cmd.Name())
 		hash := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo))
 		if hash != "" {
-			hash = c.shards.Hash(hashtag.Key(hash))
+			hash = c.shards.Hash(hash)
 		}
 		cmdsMap[hash] = append(cmdsMap[hash], cmd)
 	}
@@ -646,7 +668,7 @@ func (c *Ring) processShardPipeline(
 	ctx context.Context, hash string, cmds []Cmder, tx bool,
 ) error {
 	//TODO: retry?
-	shard, err := c.shards.GetByHash(hash)
+	shard, err := c.shards.GetByName(hash)
 	if err != nil {
 		setCmdsErr(cmds, err)
 		return err
@@ -700,7 +722,3 @@ func (c *Ring) Watch(ctx context.Context, fn func(*Tx) error, keys ...string) er
 
 	return shards[0].Client.Watch(ctx, fn, keys...)
 }
-
-func newConsistentHash(opt *RingOptions) *consistenthash.Map {
-	return consistenthash.New(opt.HashReplicas, consistenthash.Hash(opt.Hash))
-}

ring_test.go

@@ -54,8 +54,8 @@ var _ = Describe("Redis Ring", func() {
 		setRingKeys()
 
 		// Both shards should have some keys now.
-		Expect(ringShard1.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=57"))
+		Expect(ringShard1.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=56"))
-		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=43"))
+		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=44"))
 	})
 
 	It("distributes keys when using EVAL", func() {
@@ -71,8 +71,8 @@ var _ = Describe("Redis Ring", func() {
 			Expect(err).NotTo(HaveOccurred())
 		}
 
-		Expect(ringShard1.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=57"))
+		Expect(ringShard1.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=56"))
-		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=43"))
+		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=44"))
 	})
 
 	It("uses single shard when one of the shards is down", func() {
@@ -100,7 +100,7 @@ var _ = Describe("Redis Ring", func() {
 		setRingKeys()
 
 		// RingShard2 should have its keys.
-		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=43"))
+		Expect(ringShard2.Info(ctx, "keyspace").Val()).To(ContainSubstring("keys=44"))
 	})
 
 	It("supports hash tags", func() {
@@ -131,8 +131,8 @@ var _ = Describe("Redis Ring", func() {
 			}
 
 			// Both shards should have some keys now.
-			Expect(ringShard1.Info(ctx).Val()).To(ContainSubstring("keys=57"))
+			Expect(ringShard1.Info(ctx).Val()).To(ContainSubstring("keys=56"))
-			Expect(ringShard2.Info(ctx).Val()).To(ContainSubstring("keys=43"))
+			Expect(ringShard2.Info(ctx).Val()).To(ContainSubstring("keys=44"))
 		})
 
 		It("is consistent with ring", func() {
@@ -427,22 +427,22 @@ var _ = Describe("Ring watch", func() {
 	It("should discard", func() {
 		err := ring.Watch(ctx, func(tx *redis.Tx) error {
 			cmds, err := tx.TxPipelined(ctx, func(pipe redis.Pipeliner) error {
-				pipe.Set(ctx, "key1", "hello1", 0)
+				pipe.Set(ctx, "{shard}key1", "hello1", 0)
 				pipe.Discard()
-				pipe.Set(ctx, "key2", "hello2", 0)
+				pipe.Set(ctx, "{shard}key2", "hello2", 0)
 				return nil
 			})
 			Expect(err).NotTo(HaveOccurred())
 			Expect(cmds).To(HaveLen(1))
 			return err
-		}, "key1", "key2")
+		}, "{shard}key1", "{shard}key2")
 		Expect(err).NotTo(HaveOccurred())
 
-		get := ring.Get(ctx, "key1")
+		get := ring.Get(ctx, "{shard}key1")
 		Expect(get.Err()).To(Equal(redis.Nil))
 		Expect(get.Val()).To(Equal(""))
 
-		get = ring.Get(ctx, "key2")
+		get = ring.Get(ctx, "{shard}key2")
 		Expect(get.Err()).NotTo(HaveOccurred())
 		Expect(get.Val()).To(Equal("hello2"))
 	})