RedisLock.scala

// Using Rediscala library here.
import redis.RedisClient
import scala.concurrent.Future
import java.util.UUID

case class RedisLockedException(key: String) extends Exception(s"Resource '${key}' is in use.")

// This is based on the following Redis locking scheme (single instance):
// https://redis.io/topics/distlock
object RedisLock {
  val redisClient: RedisClient
  val LockKey = "some/lock/key"
  
  def withLock[T](ttl: Long)(work: => Future[T]): Future[T] = {
    val signature = UUID.randomUUID.toString
    val didAcquire = redisClient.set(LockKey, signature, NX = true, pxMilliseconds = Some(ttl))
    didAcquire.flatMap {
      case false => Future.failed(RedisLockedException(LockKey))
      case true =>
        work.flatMap { result =>
          val ownerSignature = redisClient.get[String](LockKey)
          val weOwnExistingLock = ownerSignature.map(_ == Some(signature))
          weOwnExistingLock.flatMap {
            case true => redisClient.del(LockKey).map(_ => result)
            case false => Future.successful(result)
          }
        }
    }
  }
}