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ring.go
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ring.go
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package redis
import (
"context"
"crypto/tls"
"errors"
"fmt"
"net"
"strconv"
"sync"
"sync/atomic"
"time"
"github.com/cespare/xxhash/v2"
"github.com/dgryski/go-rendezvous" //nolint
"github.com/redis/go-redis/v9/internal"
"github.com/redis/go-redis/v9/internal/hashtag"
"github.com/redis/go-redis/v9/internal/pool"
"github.com/redis/go-redis/v9/internal/rand"
)
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 options.
NewClient func(opt *Options) *Client
// ClientName will execute the `CLIENT SETNAME ClientName` command for each conn.
ClientName string
// Frequency of PING commands sent to check shards availability.
// Shard is considered down after 3 subsequent failed checks.
HeartbeatFrequency time.Duration
// NewConsistentHash returns a consistent hash that is used
// to distribute keys across the shards.
//
// See https://medium.com/@dgryski/consistent-hashing-algorithmic-tradeoffs-ef6b8e2fcae8
// for consistent hashing algorithmic tradeoffs.
NewConsistentHash func(shards []string) ConsistentHash
// Following options are copied from Options struct.
Dialer func(ctx context.Context, network, addr string) (net.Conn, error)
OnConnect func(ctx context.Context, cn *Conn) error
Protocol int
Username string
Password string
DB int
MaxRetries int
MinRetryBackoff time.Duration
MaxRetryBackoff time.Duration
DialTimeout time.Duration
ReadTimeout time.Duration
WriteTimeout time.Duration
ContextTimeoutEnabled bool
// PoolFIFO uses FIFO mode for each node connection pool GET/PUT (default LIFO).
PoolFIFO bool
PoolSize int
PoolTimeout time.Duration
MinIdleConns int
MaxIdleConns int
MaxActiveConns int
ConnMaxIdleTime time.Duration
ConnMaxLifetime time.Duration
TLSConfig *tls.Config
Limiter Limiter
DisableIndentity bool
IdentitySuffix string
UnstableResp3 bool
}
func (opt *RingOptions) init() {
if opt.NewClient == nil {
opt.NewClient = func(opt *Options) *Client {
return NewClient(opt)
}
}
if opt.HeartbeatFrequency == 0 {
opt.HeartbeatFrequency = 500 * time.Millisecond
}
if opt.NewConsistentHash == nil {
opt.NewConsistentHash = newRendezvous
}
if opt.MaxRetries == -1 {
opt.MaxRetries = 0
} else if opt.MaxRetries == 0 {
opt.MaxRetries = 3
}
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 *RingOptions) clientOptions() *Options {
return &Options{
ClientName: opt.ClientName,
Dialer: opt.Dialer,
OnConnect: opt.OnConnect,
Protocol: opt.Protocol,
Username: opt.Username,
Password: opt.Password,
DB: opt.DB,
MaxRetries: -1,
DialTimeout: opt.DialTimeout,
ReadTimeout: opt.ReadTimeout,
WriteTimeout: opt.WriteTimeout,
ContextTimeoutEnabled: opt.ContextTimeoutEnabled,
PoolFIFO: opt.PoolFIFO,
PoolSize: opt.PoolSize,
PoolTimeout: opt.PoolTimeout,
MinIdleConns: opt.MinIdleConns,
MaxIdleConns: opt.MaxIdleConns,
MaxActiveConns: opt.MaxActiveConns,
ConnMaxIdleTime: opt.ConnMaxIdleTime,
ConnMaxLifetime: opt.ConnMaxLifetime,
TLSConfig: opt.TLSConfig,
Limiter: opt.Limiter,
DisableIndentity: opt.DisableIndentity,
IdentitySuffix: opt.IdentitySuffix,
UnstableResp3: opt.UnstableResp3,
}
}
//------------------------------------------------------------------------------
type ringShard struct {
Client *Client
down int32
addr string
}
func newRingShard(opt *RingOptions, addr string) *ringShard {
clopt := opt.clientOptions()
clopt.Addr = addr
return &ringShard{
Client: opt.NewClient(clopt),
addr: addr,
}
}
func (shard *ringShard) String() string {
var state string
if shard.IsUp() {
state = "up"
} else {
state = "down"
}
return fmt.Sprintf("%s is %s", shard.Client, state)
}
func (shard *ringShard) IsDown() bool {
const threshold = 3
return atomic.LoadInt32(&shard.down) >= threshold
}
func (shard *ringShard) IsUp() bool {
return !shard.IsDown()
}
// Vote votes to set shard state and returns true if state was changed.
func (shard *ringShard) Vote(up bool) bool {
if up {
changed := shard.IsDown()
atomic.StoreInt32(&shard.down, 0)
return changed
}
if shard.IsDown() {
return false
}
atomic.AddInt32(&shard.down, 1)
return shard.IsDown()
}
//------------------------------------------------------------------------------
type ringSharding struct {
opt *RingOptions
mu sync.RWMutex
shards *ringShards
closed bool
hash ConsistentHash
numShard int
onNewNode []func(rdb *Client)
// ensures exclusive access to SetAddrs so there is no need
// to hold mu for the duration of potentially long shard creation
setAddrsMu sync.Mutex
}
type ringShards struct {
m map[string]*ringShard
list []*ringShard
}
func newRingSharding(opt *RingOptions) *ringSharding {
c := &ringSharding{
opt: opt,
}
c.SetAddrs(opt.Addrs)
return c
}
func (c *ringSharding) OnNewNode(fn func(rdb *Client)) {
c.mu.Lock()
c.onNewNode = append(c.onNewNode, fn)
c.mu.Unlock()
}
// SetAddrs replaces the shards in use, such that you can increase and
// decrease number of shards, that you use. It will reuse shards that
// existed before and close the ones that will not be used anymore.
func (c *ringSharding) SetAddrs(addrs map[string]string) {
c.setAddrsMu.Lock()
defer c.setAddrsMu.Unlock()
cleanup := func(shards map[string]*ringShard) {
for addr, shard := range shards {
if err := shard.Client.Close(); err != nil {
internal.Logger.Printf(context.Background(), "shard.Close %s failed: %s", addr, err)
}
}
}
c.mu.RLock()
if c.closed {
c.mu.RUnlock()
return
}
existing := c.shards
c.mu.RUnlock()
shards, created, unused := c.newRingShards(addrs, existing)
c.mu.Lock()
if c.closed {
cleanup(created)
c.mu.Unlock()
return
}
c.shards = shards
c.rebalanceLocked()
c.mu.Unlock()
cleanup(unused)
}
func (c *ringSharding) newRingShards(
addrs map[string]string, existing *ringShards,
) (shards *ringShards, created, unused map[string]*ringShard) {
shards = &ringShards{m: make(map[string]*ringShard, len(addrs))}
created = make(map[string]*ringShard) // indexed by addr
unused = make(map[string]*ringShard) // indexed by addr
if existing != nil {
for _, shard := range existing.list {
unused[shard.addr] = shard
}
}
for name, addr := range addrs {
if shard, ok := unused[addr]; ok {
shards.m[name] = shard
delete(unused, addr)
} else {
shard := newRingShard(c.opt, addr)
shards.m[name] = shard
created[addr] = shard
for _, fn := range c.onNewNode {
fn(shard.Client)
}
}
}
for _, shard := range shards.m {
shards.list = append(shards.list, shard)
}
return
}
func (c *ringSharding) List() []*ringShard {
var list []*ringShard
c.mu.RLock()
if !c.closed {
list = c.shards.list
}
c.mu.RUnlock()
return list
}
func (c *ringSharding) Hash(key string) string {
key = hashtag.Key(key)
var hash string
c.mu.RLock()
defer c.mu.RUnlock()
if c.numShard > 0 {
hash = c.hash.Get(key)
}
return hash
}
func (c *ringSharding) GetByKey(key string) (*ringShard, error) {
key = hashtag.Key(key)
c.mu.RLock()
defer c.mu.RUnlock()
if c.closed {
return nil, pool.ErrClosed
}
if c.numShard == 0 {
return nil, errRingShardsDown
}
shardName := c.hash.Get(key)
if shardName == "" {
return nil, errRingShardsDown
}
return c.shards.m[shardName], nil
}
func (c *ringSharding) GetByName(shardName string) (*ringShard, error) {
if shardName == "" {
return c.Random()
}
c.mu.RLock()
defer c.mu.RUnlock()
return c.shards.m[shardName], nil
}
func (c *ringSharding) Random() (*ringShard, error) {
return c.GetByKey(strconv.Itoa(rand.Int()))
}
// Heartbeat monitors state of each shard in the ring.
func (c *ringSharding) Heartbeat(ctx context.Context, frequency time.Duration) {
ticker := time.NewTicker(frequency)
defer ticker.Stop()
for {
select {
case <-ticker.C:
var rebalance bool
for _, shard := range c.List() {
err := shard.Client.Ping(ctx).Err()
isUp := err == nil || err == pool.ErrPoolTimeout
if shard.Vote(isUp) {
internal.Logger.Printf(ctx, "ring shard state changed: %s", shard)
rebalance = true
}
}
if rebalance {
c.mu.Lock()
c.rebalanceLocked()
c.mu.Unlock()
}
case <-ctx.Done():
return
}
}
}
// rebalanceLocked removes dead shards from the Ring.
// Requires c.mu locked.
func (c *ringSharding) rebalanceLocked() {
if c.closed {
return
}
if c.shards == nil {
return
}
liveShards := make([]string, 0, len(c.shards.m))
for name, shard := range c.shards.m {
if shard.IsUp() {
liveShards = append(liveShards, name)
}
}
c.hash = c.opt.NewConsistentHash(liveShards)
c.numShard = len(liveShards)
}
func (c *ringSharding) Len() int {
c.mu.RLock()
defer c.mu.RUnlock()
return c.numShard
}
func (c *ringSharding) Close() error {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return nil
}
c.closed = true
var firstErr error
for _, shard := range c.shards.list {
if err := shard.Client.Close(); err != nil && firstErr == nil {
firstErr = err
}
}
c.hash = nil
c.shards = nil
c.numShard = 0
return firstErr
}
//------------------------------------------------------------------------------
// Ring is a Redis client that uses consistent hashing to distribute
// keys across multiple Redis servers (shards). It's safe for
// concurrent use by multiple goroutines.
//
// Ring monitors the state of each shard and removes dead shards from
// the ring. When a shard comes online it is added back to the ring. This
// gives you maximum availability and partition tolerance, but no
// consistency between different shards or even clients. Each client
// uses shards that are available to the client and does not do any
// coordination when shard state is changed.
//
// Ring should be used when you need multiple Redis servers for caching
// and can tolerate losing data when one of the servers dies.
// Otherwise you should use Redis Cluster.
type Ring struct {
cmdable
hooksMixin
opt *RingOptions
sharding *ringSharding
cmdsInfoCache *cmdsInfoCache
heartbeatCancelFn context.CancelFunc
}
func NewRing(opt *RingOptions) *Ring {
opt.init()
hbCtx, hbCancel := context.WithCancel(context.Background())
ring := Ring{
opt: opt,
sharding: newRingSharding(opt),
heartbeatCancelFn: hbCancel,
}
ring.cmdsInfoCache = newCmdsInfoCache(ring.cmdsInfo)
ring.cmdable = ring.Process
ring.initHooks(hooks{
process: ring.process,
pipeline: func(ctx context.Context, cmds []Cmder) error {
return ring.generalProcessPipeline(ctx, cmds, false)
},
txPipeline: func(ctx context.Context, cmds []Cmder) error {
return ring.generalProcessPipeline(ctx, cmds, true)
},
})
go ring.sharding.Heartbeat(hbCtx, opt.HeartbeatFrequency)
return &ring
}
func (c *Ring) SetAddrs(addrs map[string]string) {
c.sharding.SetAddrs(addrs)
}
// Do create a Cmd from the args and processes the cmd.
func (c *Ring) Do(ctx context.Context, args ...interface{}) *Cmd {
cmd := NewCmd(ctx, args...)
_ = c.Process(ctx, cmd)
return cmd
}
func (c *Ring) Process(ctx context.Context, cmd Cmder) error {
err := c.processHook(ctx, cmd)
cmd.SetErr(err)
return err
}
// Options returns read-only Options that were used to create the client.
func (c *Ring) Options() *RingOptions {
return c.opt
}
func (c *Ring) retryBackoff(attempt int) time.Duration {
return internal.RetryBackoff(attempt, c.opt.MinRetryBackoff, c.opt.MaxRetryBackoff)
}
// PoolStats returns accumulated connection pool stats.
func (c *Ring) PoolStats() *PoolStats {
shards := c.sharding.List()
var acc PoolStats
for _, shard := range shards {
s := shard.Client.connPool.Stats()
acc.Hits += s.Hits
acc.Misses += s.Misses
acc.Timeouts += s.Timeouts
acc.TotalConns += s.TotalConns
acc.IdleConns += s.IdleConns
}
return &acc
}
// Len returns the current number of shards in the ring.
func (c *Ring) Len() int {
return c.sharding.Len()
}
// Subscribe subscribes the client to the specified channels.
func (c *Ring) Subscribe(ctx context.Context, channels ...string) *PubSub {
if len(channels) == 0 {
panic("at least one channel is required")
}
shard, err := c.sharding.GetByKey(channels[0])
if err != nil {
// TODO: return PubSub with sticky error
panic(err)
}
return shard.Client.Subscribe(ctx, channels...)
}
// PSubscribe subscribes the client to the given patterns.
func (c *Ring) PSubscribe(ctx context.Context, channels ...string) *PubSub {
if len(channels) == 0 {
panic("at least one channel is required")
}
shard, err := c.sharding.GetByKey(channels[0])
if err != nil {
// TODO: return PubSub with sticky error
panic(err)
}
return shard.Client.PSubscribe(ctx, channels...)
}
// SSubscribe Subscribes the client to the specified shard channels.
func (c *Ring) SSubscribe(ctx context.Context, channels ...string) *PubSub {
if len(channels) == 0 {
panic("at least one channel is required")
}
shard, err := c.sharding.GetByKey(channels[0])
if err != nil {
// TODO: return PubSub with sticky error
panic(err)
}
return shard.Client.SSubscribe(ctx, channels...)
}
func (c *Ring) OnNewNode(fn func(rdb *Client)) {
c.sharding.OnNewNode(fn)
}
// ForEachShard concurrently calls the fn on each live shard in the ring.
// It returns the first error if any.
func (c *Ring) ForEachShard(
ctx context.Context,
fn func(ctx context.Context, client *Client) error,
) error {
shards := c.sharding.List()
var wg sync.WaitGroup
errCh := make(chan error, 1)
for _, shard := range shards {
if shard.IsDown() {
continue
}
wg.Add(1)
go func(shard *ringShard) {
defer wg.Done()
err := fn(ctx, shard.Client)
if err != nil {
select {
case errCh <- err:
default:
}
}
}(shard)
}
wg.Wait()
select {
case err := <-errCh:
return err
default:
return nil
}
}
func (c *Ring) cmdsInfo(ctx context.Context) (map[string]*CommandInfo, error) {
shards := c.sharding.List()
var firstErr error
for _, shard := range shards {
cmdsInfo, err := shard.Client.Command(ctx).Result()
if err == nil {
return cmdsInfo, nil
}
if firstErr == nil {
firstErr = err
}
}
if firstErr == nil {
return nil, errRingShardsDown
}
return nil, firstErr
}
func (c *Ring) cmdShard(ctx context.Context, cmd Cmder) (*ringShard, error) {
pos := cmdFirstKeyPos(cmd)
if pos == 0 {
return c.sharding.Random()
}
firstKey := cmd.stringArg(pos)
return c.sharding.GetByKey(firstKey)
}
func (c *Ring) process(ctx context.Context, cmd Cmder) error {
var lastErr error
for attempt := 0; attempt <= c.opt.MaxRetries; attempt++ {
if attempt > 0 {
if err := internal.Sleep(ctx, c.retryBackoff(attempt)); err != nil {
return err
}
}
shard, err := c.cmdShard(ctx, cmd)
if err != nil {
return err
}
lastErr = shard.Client.Process(ctx, cmd)
if lastErr == nil || !shouldRetry(lastErr, cmd.readTimeout() == nil) {
return lastErr
}
}
return lastErr
}
func (c *Ring) Pipelined(ctx context.Context, fn func(Pipeliner) error) ([]Cmder, error) {
return c.Pipeline().Pipelined(ctx, fn)
}
func (c *Ring) Pipeline() Pipeliner {
pipe := Pipeline{
exec: pipelineExecer(c.processPipelineHook),
}
pipe.init()
return &pipe
}
func (c *Ring) TxPipelined(ctx context.Context, fn func(Pipeliner) error) ([]Cmder, error) {
return c.TxPipeline().Pipelined(ctx, fn)
}
func (c *Ring) TxPipeline() Pipeliner {
pipe := Pipeline{
exec: func(ctx context.Context, cmds []Cmder) error {
cmds = wrapMultiExec(ctx, cmds)
return c.processTxPipelineHook(ctx, cmds)
},
}
pipe.init()
return &pipe
}
func (c *Ring) generalProcessPipeline(
ctx context.Context, cmds []Cmder, tx bool,
) error {
if tx {
// Trim multi .. exec.
cmds = cmds[1 : len(cmds)-1]
}
cmdsMap := make(map[string][]Cmder)
for _, cmd := range cmds {
hash := cmd.stringArg(cmdFirstKeyPos(cmd))
if hash != "" {
hash = c.sharding.Hash(hash)
}
cmdsMap[hash] = append(cmdsMap[hash], cmd)
}
var wg sync.WaitGroup
for hash, cmds := range cmdsMap {
wg.Add(1)
go func(hash string, cmds []Cmder) {
defer wg.Done()
// TODO: retry?
shard, err := c.sharding.GetByName(hash)
if err != nil {
setCmdsErr(cmds, err)
return
}
if tx {
cmds = wrapMultiExec(ctx, cmds)
_ = shard.Client.processTxPipelineHook(ctx, cmds)
} else {
_ = shard.Client.processPipelineHook(ctx, cmds)
}
}(hash, cmds)
}
wg.Wait()
return cmdsFirstErr(cmds)
}
func (c *Ring) Watch(ctx context.Context, fn func(*Tx) error, keys ...string) error {
if len(keys) == 0 {
return fmt.Errorf("redis: Watch requires at least one key")
}
var shards []*ringShard
for _, key := range keys {
if key != "" {
shard, err := c.sharding.GetByKey(hashtag.Key(key))
if err != nil {
return err
}
shards = append(shards, shard)
}
}
if len(shards) == 0 {
return fmt.Errorf("redis: Watch requires at least one shard")
}
if len(shards) > 1 {
for _, shard := range shards[1:] {
if shard.Client != shards[0].Client {
err := fmt.Errorf("redis: Watch requires all keys to be in the same shard")
return err
}
}
}
return shards[0].Client.Watch(ctx, fn, keys...)
}
// Close closes the ring client, releasing any open resources.
//
// It is rare to Close a Ring, as the Ring is meant to be long-lived
// and shared between many goroutines.
func (c *Ring) Close() error {
c.heartbeatCancelFn()
return c.sharding.Close()
}