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main.go
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main.go
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package main
import (
"flag"
"fmt"
"log"
"math/rand"
"net/http"
"os"
"strconv"
"time"
sw "github.com/RussellLuo/slidingwindow"
"github.com/go-redis/redis"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
var (
size time.Duration
limit int64
resourceName string
syncInterval time.Duration
scale int
redisAddr string
listenAddr string
requestAllowed = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: "slidingwindow",
Name: "requests_total",
Help: "count of requests, partitioned by resource, limiter and allow result.",
},
[]string{"resource", "limiter", "allow"},
)
)
type RedisDatastore struct {
client redis.Cmdable
ttl time.Duration
}
func NewRedisDatastore(client redis.Cmdable, ttl time.Duration) *RedisDatastore {
return &RedisDatastore{client: client, ttl: ttl}
}
func (d *RedisDatastore) fullKey(key string, start int64) string {
return fmt.Sprintf("%s@%d", key, start)
}
func (d *RedisDatastore) Add(key string, start, value int64) (int64, error) {
k := d.fullKey(key, start)
c, err := d.client.IncrBy(k, value).Result()
if err != nil {
return 0, err
}
// Ignore the possible error from EXPIRE command.
d.client.Expire(k, d.ttl).Result() // nolint:errcheck
return c, err
}
func (d *RedisDatastore) Get(key string, start int64) (int64, error) {
k := d.fullKey(key, start)
value, err := d.client.Get(k).Result()
if err != nil {
if err == redis.Nil {
// redis.Nil is not an error, it only indicates the key does not exist.
err = nil
}
return 0, err
}
return strconv.ParseInt(value, 10, 64)
}
type Limiter struct {
name string
lim *sw.Limiter
stop sw.StopFunc
}
func parseFlags() {
var (
sizeFlag = flag.String("size", "1s", "The time duration during which limit takes effect.")
limitFlag = flag.Int64("limit", 20, "The maximum events permitted.")
resourceFlag = flag.String("resource", "test", "The name of the resource that will be limited.")
syncFlag = flag.String("sync", "200ms", "The time duration of sync interval.")
scaleFlag = flag.Int("scale", 2, "The number of limiters that will work concurrently.")
redisFlag = flag.String("redis", "localhost:6379", "The address of the Redis server.")
listenFlag = flag.String("listen", "", "The listen address of the HTTP server.")
)
flag.Parse()
var err error
size, err = time.ParseDuration(*sizeFlag)
if err != nil {
panic(err)
}
syncInterval, err = time.ParseDuration(*syncFlag)
if err != nil {
panic(err)
}
limit = *limitFlag
resourceName = *resourceFlag
scale = *scaleFlag
redisAddr = *redisFlag
listenAddr = *listenFlag
if listenAddr == "" {
fmt.Println(`Flag "-listen" is required`)
os.Exit(1)
}
}
func newLimiters() (limiters []Limiter) {
store := NewRedisDatastore(
redis.NewClient(&redis.Options{
Addr: redisAddr,
}),
2*size, // twice of size is just enough.
)
for i := 0; i < scale; i++ {
lim, stop := sw.NewLimiter(size, limit, func() (sw.Window, sw.StopFunc) {
return sw.NewSyncWindow(resourceName, sw.NewBlockingSynchronizer(store, syncInterval))
})
limiters = append(limiters, Limiter{
name: fmt.Sprintf("lim-%d", i),
lim: lim,
stop: stop,
})
}
return
}
func main() {
log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds | log.Llongfile)
parseFlags()
limiters := newLimiters()
defer func() {
for _, limiter := range limiters {
limiter.stop()
}
}()
prometheus.MustRegister(requestAllowed)
http.Handle("/metrics", promhttp.Handler())
http.HandleFunc("/allow", func(w http.ResponseWriter, r *http.Request) {
randI := rand.Intn(scale)
ok := limiters[randI].lim.Allow()
fmt.Fprintf(w, "%s: %v", limiters[randI].name, ok)
requestAllowed.WithLabelValues(resourceName, limiters[randI].name, strconv.FormatBool(ok)).Inc()
})
log.Fatal(http.ListenAndServe(listenAddr, nil))
}