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store.go
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store.go
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package redis
import (
"errors"
"time"
"github.com/garyburd/redigo/redis"
)
var (
PrefixKey = "ratelimit:"
ErrUnreachable = errors.New("redis is unreachable")
RetryAfter = time.Second
)
const skipOnUnhealthy = 1000
type bucketStore struct {
pool *redis.Pool
rate int
windowSeconds int
retryAfter *time.Time
}
// New creates new in-memory token bucket store.
func New(pool *redis.Pool) *bucketStore {
return &bucketStore{
pool: pool,
}
}
func (s *bucketStore) InitRate(rate int, window time.Duration) {
s.rate = rate
s.windowSeconds = int(window / time.Second)
if s.windowSeconds <= 1 {
s.windowSeconds = 1
}
}
// Take implements TokenBucketStore interface. It takes token from a bucket
// referenced by a given key, if available.
func (s *bucketStore) Take(key string) (bool, int, time.Time, error) {
if s.retryAfter != nil {
if s.retryAfter.After(time.Now()) {
return false, 0, time.Time{}, ErrUnreachable
}
s.retryAfter = nil
}
c := s.pool.Get()
defer c.Close()
// Number of tokens in the bucket.
bucketLen, err := redis.Int(c.Do("LLEN", PrefixKey+key))
if err != nil {
next := time.Now().Add(time.Second)
s.retryAfter = &next
return false, 0, time.Time{}, err
}
// Bucket is full.
if bucketLen >= s.rate {
return false, 0, time.Time{}, nil
}
if bucketLen > 0 {
// Bucket most probably exists, try to push a new token into it.
// If RPUSHX returns 0 (ie. key expired between LLEN and RPUSHX), we need
// to fall-back to RPUSH without returning error.
c.Send("MULTI")
c.Send("RPUSHX", PrefixKey+key, "")
reply, err := redis.Ints(c.Do("EXEC"))
if err != nil {
next := time.Now().Add(time.Second)
s.retryAfter = &next
return false, 0, time.Time{}, err
}
bucketLen = reply[0]
if bucketLen > 0 {
return true, s.rate - bucketLen - 1, time.Time{}, nil
}
}
c.Send("MULTI")
c.Send("RPUSH", PrefixKey+key, "")
c.Send("EXPIRE", PrefixKey+key, s.windowSeconds)
if _, err := c.Do("EXEC"); err != nil {
next := time.Now().Add(time.Second)
s.retryAfter = &next
return false, 0, time.Time{}, err
}
return true, s.rate - bucketLen - 1, time.Time{}, nil
}