DTB (Distributed Token Bucket)

This library provides a token bucket that works in a distributed way and without relying on lua scripts in Redis.

Description

The bucket is maintained in Redis - each client attempts to acquire an expiring lock and add tokens to the bucket. If the lock does expire (meaning that the owner has likely perished) then the next client to visit the lock acquires it. Currently the locks expire after a duration of twice the token cadence has elapsed and to prevent expiration the client that owns the lock pushes the expiration forward on each addition of tokens.

Usage

Here's a small example of using this in practice:

func main() {
  redisClient := redis.NewClient(
    &redis.Options{
      Addr:     "redis:6379",
      Password: "", // no password set
      DB:       0,  // use default DB
    },
  )

  dtb := NewDTB(
    "my-token-bucket",                 // the name of the bucket
    1000,                              // the capacity
    time.Duration(1*time.Second),      // the cadence to add tokens
    redisClient                        // the redis client
  )

  for {
    fmt.Println("--------------------------------")
    // blocking call to "get" a token
    err := dtb.GetToken()

    if err != nil {
      fmt.Fatal(err)
    }
    fmt.Println("Got a token!")
    time.Sleep(time.Duration(500 * time.Millisecond))
    fmt.Println("--------------------------------")
  }
}

TODO:

• Add #Shutdown for nicely exiting the goroutine of the "maintainer"
• Add some smart catchup features if possible
• Consider making the lockDuration configurable