package redis import ( "errors" "fmt" "math/rand" "strconv" "sync" "sync/atomic" "time" "github.com/go-redis/redis/internal" "github.com/go-redis/redis/internal/consistenthash" "github.com/go-redis/redis/internal/hashtag" "github.com/go-redis/redis/internal/pool" ) var errRingShardsDown = errors.New("redis: all ring shards are down") // 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 // Frequency of PING commands sent to check shards availability. // Shard is considered down after 3 subsequent failed checks. HeartbeatFrequency time.Duration // Following options are copied from Options struct. OnConnect func(*Conn) error DB int Password string MaxRetries int MinRetryBackoff time.Duration MaxRetryBackoff time.Duration DialTimeout time.Duration ReadTimeout time.Duration WriteTimeout time.Duration PoolSize int PoolTimeout time.Duration IdleTimeout time.Duration IdleCheckFrequency time.Duration } func (opt *RingOptions) init() { if opt.HeartbeatFrequency == 0 { opt.HeartbeatFrequency = 500 * time.Millisecond } 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{ OnConnect: opt.OnConnect, DB: opt.DB, Password: opt.Password, DialTimeout: opt.DialTimeout, ReadTimeout: opt.ReadTimeout, WriteTimeout: opt.WriteTimeout, PoolSize: opt.PoolSize, PoolTimeout: opt.PoolTimeout, IdleTimeout: opt.IdleTimeout, IdleCheckFrequency: opt.IdleCheckFrequency, } } type ringShard struct { Client *Client down int32 } 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() } // Ring is a Redis client that uses constistent 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 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 opt *RingOptions nreplicas int mu sync.RWMutex hash *consistenthash.Map shards map[string]*ringShard shardsList []*ringShard cmdsInfoOnce internal.Once cmdsInfo map[string]*CommandInfo closed bool } func NewRing(opt *RingOptions) *Ring { const nreplicas = 100 opt.init() ring := &Ring{ opt: opt, nreplicas: nreplicas, hash: consistenthash.New(nreplicas, nil), shards: make(map[string]*ringShard), } ring.setProcessor(ring.Process) for name, addr := range opt.Addrs { clopt := opt.clientOptions() clopt.Addr = addr ring.addShard(name, NewClient(clopt)) } go ring.heartbeat() return ring } func (c *Ring) addShard(name string, cl *Client) { shard := &ringShard{Client: cl} c.mu.Lock() c.hash.Add(name) c.shards[name] = shard c.shardsList = append(c.shardsList, shard) c.mu.Unlock() } // 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 { c.mu.RLock() shards := c.shardsList c.mu.RUnlock() 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.FreeConns += s.FreeConns } return &acc } // Subscribe subscribes the client to the specified channels. func (c *Ring) Subscribe(channels ...string) *PubSub { if len(channels) == 0 { panic("at least one channel is required") } shard, err := c.shardByKey(channels[0]) if err != nil { // TODO: return PubSub with sticky error panic(err) } return shard.Client.Subscribe(channels...) } // PSubscribe subscribes the client to the given patterns. func (c *Ring) PSubscribe(channels ...string) *PubSub { if len(channels) == 0 { panic("at least one channel is required") } shard, err := c.shardByKey(channels[0]) if err != nil { // TODO: return PubSub with sticky error panic(err) } return shard.Client.PSubscribe(channels...) } // ForEachShard concurrently calls the fn on each live shard in the ring. // It returns the first error if any. func (c *Ring) ForEachShard(fn func(client *Client) error) error { c.mu.RLock() shards := c.shardsList c.mu.RUnlock() 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(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) cmdInfo(name string) *CommandInfo { err := c.cmdsInfoOnce.Do(func() error { c.mu.RLock() shards := c.shardsList c.mu.RUnlock() var firstErr error for _, shard := range shards { cmdsInfo, err := shard.Client.Command().Result() if err == nil { c.cmdsInfo = cmdsInfo return nil } if firstErr == nil { firstErr = err } } return firstErr }) if err != nil { return nil } info := c.cmdsInfo[name] if info == nil { internal.Logf("info for cmd=%s not found", name) } return info } func (c *Ring) shardByKey(key string) (*ringShard, error) { key = hashtag.Key(key) c.mu.RLock() if c.closed { c.mu.RUnlock() return nil, pool.ErrClosed } name := c.hash.Get(key) if name == "" { c.mu.RUnlock() return nil, errRingShardsDown } shard := c.shards[name] c.mu.RUnlock() return shard, nil } func (c *Ring) randomShard() (*ringShard, error) { return c.shardByKey(strconv.Itoa(rand.Int())) } func (c *Ring) shardByName(name string) (*ringShard, error) { if name == "" { return c.randomShard() } c.mu.RLock() shard := c.shards[name] c.mu.RUnlock() return shard, nil } func (c *Ring) cmdShard(cmd Cmder) (*ringShard, error) { cmdInfo := c.cmdInfo(cmd.Name()) firstKey := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo)) return c.shardByKey(firstKey) } func (c *Ring) Process(cmd Cmder) error { shard, err := c.cmdShard(cmd) if err != nil { cmd.setErr(err) return err } return shard.Client.Process(cmd) } // rebalance removes dead shards from the Ring. func (c *Ring) rebalance() { hash := consistenthash.New(c.nreplicas, nil) for name, shard := range c.shards { if shard.IsUp() { hash.Add(name) } } c.mu.Lock() c.hash = hash c.mu.Unlock() } // heartbeat monitors state of each shard in the ring. func (c *Ring) heartbeat() { ticker := time.NewTicker(c.opt.HeartbeatFrequency) defer ticker.Stop() for range ticker.C { var rebalance bool c.mu.RLock() if c.closed { c.mu.RUnlock() break } shards := c.shardsList c.mu.RUnlock() for _, shard := range shards { err := shard.Client.Ping().Err() if shard.Vote(err == nil || err == pool.ErrPoolTimeout) { internal.Logf("ring shard state changed: %s", shard) rebalance = true } } if rebalance { c.rebalance() } } } // 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.mu.Lock() defer c.mu.Unlock() if c.closed { return nil } c.closed = true var firstErr error for _, shard := range c.shards { if err := shard.Client.Close(); err != nil && firstErr == nil { firstErr = err } } c.hash = nil c.shards = nil c.shardsList = nil return firstErr } func (c *Ring) Pipeline() Pipeliner { pipe := Pipeline{ exec: c.pipelineExec, } pipe.setProcessor(pipe.Process) return &pipe } func (c *Ring) Pipelined(fn func(Pipeliner) error) ([]Cmder, error) { return c.Pipeline().Pipelined(fn) } func (c *Ring) pipelineExec(cmds []Cmder) error { cmdsMap := make(map[string][]Cmder) for _, cmd := range cmds { cmdInfo := c.cmdInfo(cmd.Name()) name := cmd.stringArg(cmdFirstKeyPos(cmd, cmdInfo)) if name != "" { name = c.hash.Get(hashtag.Key(name)) } cmdsMap[name] = append(cmdsMap[name], cmd) } for attempt := 0; attempt <= c.opt.MaxRetries; attempt++ { if attempt > 0 { time.Sleep(c.retryBackoff(attempt)) } var failedCmdsMap map[string][]Cmder for name, cmds := range cmdsMap { shard, err := c.shardByName(name) if err != nil { setCmdsErr(cmds, err) continue } cn, _, err := shard.Client.getConn() if err != nil { setCmdsErr(cmds, err) continue } canRetry, err := shard.Client.pipelineProcessCmds(cn, cmds) if err == nil || internal.IsRedisError(err) { _ = shard.Client.connPool.Put(cn) continue } _ = shard.Client.connPool.Remove(cn) if canRetry && internal.IsRetryableError(err, true) { if failedCmdsMap == nil { failedCmdsMap = make(map[string][]Cmder) } failedCmdsMap[name] = cmds } } if len(failedCmdsMap) == 0 { break } cmdsMap = failedCmdsMap } return firstCmdsErr(cmds) } func (c *Ring) TxPipeline() Pipeliner { panic("not implemented") } func (c *Ring) TxPipelined(fn func(Pipeliner) error) ([]Cmder, error) { panic("not implemented") }