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redis.go
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redis.go
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package cache
import (
"context"
"errors"
"github.com/vmihailenco/msgpack/v5"
"math/rand"
"strings"
"time"
"github.com/gomodule/redigo/redis"
)
// Redis cache adaptor based on redigo
type Redis struct {
// Pool redigo redis pool
Pool *redis.Pool
// Prefix of key
Prefix string
// LockPrefix prefix of lock key, default "!lock!"
LockPrefix string
// DelayFunc is used to decide the amount of time to wait between lock retries.
DelayFunc func(tries int) time.Duration
// SkipLock skips redis lock that manages call suppression for Race method,
// which result function to be executed immediately.
// This will skip the extra cost of redis lock, if you do not need suppression
// across multiple servers
SkipLock bool
}
const (
defaultMinRetryDelayMilliSec = 50
defaultMaxRetryDelayMilliSec = 200
defaultLockPrefix = "!lock!"
)
type lockRes struct {
_msgpack struct{} `msgpack:",omitempty"`
Res []byte
Err error
}
// NewRedis creates redis cache from redigo redis pool
func NewRedis(pool *redis.Pool) *Redis {
return &Redis{
Pool: pool,
}
}
// Get implements the Get method
func (c *Redis) Get(key string) (res []byte, err error) {
var conn = c.Pool.Get()
defer conn.Close()
res, err = redis.Bytes(conn.Do("GET", c.Prefix+key))
if err == redis.ErrNil {
err = ErrNotFound
}
return
}
// Fetch get value and remaining ttl by key
func (c *Redis) Fetch(key string) (value []byte, ttl time.Duration, err error) {
var conn = c.Pool.Get()
defer conn.Close()
if err = conn.Send("GET", c.Prefix+key); err != nil {
return
}
if err = conn.Send("PTTL", c.Prefix+key); err != nil {
return
}
if err = conn.Flush(); err != nil {
return
}
if value, err = redis.Bytes(conn.Receive()); err != nil {
if err == redis.ErrNil {
err = ErrNotFound
}
return
}
var pTTL int64
if pTTL, err = redis.Int64(conn.Receive()); err != nil {
return
}
ttl = fromMilliSec(pTTL)
return
}
// Set implements the Set method
func (c *Redis) Set(key string, value []byte, ttl time.Duration) error {
var conn = c.Pool.Get()
defer conn.Close()
if _, err := conn.Do("PSETEX", c.Prefix+key, toMilliSec(ttl), value); err != nil {
return err
}
return nil
}
// Del implements the Del method
func (c *Redis) Del(keys ...string) error {
var keyArgs []interface{}
for _, key := range keys {
keyArgs = append(keyArgs, c.Prefix+key)
}
if len(keyArgs) > 0 {
var conn = c.Pool.Get()
defer conn.Close()
if _, err := conn.Do("DEL", keyArgs...); err != nil {
return err
}
}
return nil
}
// Clear implements the Clear method by SCAN keys under prefix and batched DEL
func (c *Redis) Clear() (err error) {
timeout := time.Minute * 10
ttl := time.Millisecond * 300
start := time.Now()
_, err = c.Race("!clear!", func() (b []byte, err error) {
err = c.delByPattern(c.Prefix+"*", 5000, timeout)
return
}, timeout, ttl)
// make sure elapsed time > suppression ttl
if elapsed := time.Since(start); ttl > elapsed {
time.Sleep(ttl - elapsed)
}
return
}
// Close implements the Close method
func (c *Redis) Close() error {
return c.Pool.Close()
}
// Race implements the Race method using SEX NX
func (c *Redis) Race(
key string, fn func() ([]byte, error), waitFor, ttl time.Duration,
) (value []byte, err error) {
if c.SkipLock {
return fn()
}
var (
retries int
lockKey = c.lockPrefix() + key
ctx, cancel = context.WithTimeout(context.Background(), waitFor)
)
defer cancel()
for {
resp, locked, e := c.lock(lockKey, waitFor)
if e != nil {
// if redis upstream failed, handle directly
// instead of crashing downstream consumers
return fn()
}
if locked {
value, err = fn()
if e := c.setRaceResp(lockKey, value, err, ttl); e != nil {
err = e
}
return
} else if len(resp) > 1 || resp[0] != '1' {
if ok, v, e := c.parseRaceResp(resp); ok {
value = v
err = e
return
}
}
retries++
delay := c.delayFunc(retries)
if maxDelay := ttl - defaultMinRetryDelayMilliSec; delay > maxDelay {
// delay should be within ttl
delay = maxDelay
}
time.Sleep(delay)
if err = ctx.Err(); err != nil {
return
}
}
}
func (c *Redis) delByPattern(pattern string, n int, timeout time.Duration) (err error) {
var conn = c.Pool.Get()
defer conn.Close()
var (
iter = 0
lockPrefix = c.lockPrefix()
start = time.Now()
)
for {
var arr []interface{}
if arr, err = redis.Values(conn.Do("SCAN", iter, "MATCH", pattern, "COUNT", n)); err != nil {
return err
}
iter, _ = redis.Int(arr[0], nil)
var keys, _ = redis.Strings(arr[1], nil)
var delKeys []string
for _, key := range keys {
if strings.HasPrefix(key, lockPrefix) {
continue // should skip delete lock keys
}
delKeys = append(delKeys, key)
}
if len(delKeys) > 0 {
if _, err = conn.Do("DEL", redis.Args{}.AddFlat(delKeys)...); err != nil {
return err
}
}
if iter == 0 {
break
}
if time.Since(start) > timeout {
return errors.New("timeout")
}
}
return
}
func (c *Redis) lock(
key string, timeout time.Duration,
) (value []byte, locked bool, err error) {
var conn = c.Pool.Get()
defer conn.Close()
if err = conn.Send("SET", key, "1", "PX", toMilliSec(timeout), "NX"); err != nil {
return
}
if err = conn.Send("GET", key); err != nil {
return
}
if err = conn.Flush(); err != nil {
return
}
if ok, e := redis.String(conn.Receive()); ok == "OK" && e == nil {
locked = true
}
if value, err = redis.Bytes(conn.Receive()); err != nil {
return
}
return
}
func (c *Redis) setRaceResp(key string, value []byte, e error, ttl time.Duration) (err error) {
var (
p = &lockRes{Res: value, Err: e}
b []byte
)
if b, err = msgpack.Marshal(p); err != nil {
return
}
var conn = c.Pool.Get()
defer conn.Close()
if _, err = conn.Do("PSETEX", key, toMilliSec(ttl), b); err != nil {
return
}
return
}
func (c *Redis) parseRaceResp(resp []byte) (ok bool, value []byte, err error) {
p := &lockRes{}
if e := msgpack.Unmarshal(resp, p); e != nil {
return
}
ok = true
value = p.Res
err = p.Err
return
}
func (c *Redis) lockPrefix() string {
if c.LockPrefix != "" {
return c.LockPrefix
}
return defaultLockPrefix
}
func (c *Redis) delayFunc(retries int) time.Duration {
if c.DelayFunc != nil {
return c.DelayFunc(retries)
}
return time.Duration(rand.Intn(
defaultMaxRetryDelayMilliSec-defaultMinRetryDelayMilliSec,
)+defaultMinRetryDelayMilliSec) * time.Millisecond
}
func toMilliSec(d time.Duration) int64 {
return int64(d / time.Millisecond)
}
func fromMilliSec(pTTL int64) time.Duration {
return time.Duration(pTTL) * time.Millisecond
}