scala - 在 Scala 中处理多个 Future

Question

我目前有一种基于 Future[String] 更新 Redis 表的方法。

  def update(key: String, timeStamp: Long, jsonStringF: Future[String], redisClient: RedisClient) = {

    jsonStringF.map { jsonString =>
      val historyKey = "history." + key
      val tempKey = "temp." + key

      val tran = redisClient.transaction()
      tran.zadd(historyKey, (timeStamp, jsonString))
      tran.del(tempKey)
      val f = tran.exec()
      f.onComplete {
        case Success(suc) => dlogger.info(s"Updated $historyKey and deleted $tempKey successfully ....")
        case Failure(ex) => dlogger.warn(s"Error updating tables", ex)
      }
    }
  } 

现在我有两个 Future[String] (jsonStringF1 和 jsonStringF2)，我想更新两个不同的表。

  def update(key: String, timeStamp: Long, jsonStringF1: Future[String], jsonStringF2: Future[String], redisClient: RedisClient) = {
 ....

}

我想用 jsonStringF2 中的 String 更新另一个表("another."+ key)。我怎样才能做到这一点 ？

更新:下面的代码正确吗？

  def update(tableKey: String, timeStamp: Long,  jsonStringF1: Future[String], jsonStringF2: Future[String], redisClient: RedisClient) =
  {

    for {
      a <- jsonStringF1
      t <- jsonStringF2

      historyKey = "history." + tableKey
      anotherKey = "another." + tableKey + 

      tempKey = "temp." + tableKey
      tran = redisClient.transaction()
      _ = tran.zadd(historyKey, (timeStamp, a))
      _ = tran.zadd(anotherKey, (timeStamp, t))
      _ = tran.del(tempKey)
      f = tran.exec()
    } yield ()
  }

Answer 1

1. 您可以使用 for 循环，如您所描述的

   def update(tableKey: String, timeStamp: Long,  jsonStringF1: Future[String], jsonStringF2:Future[String], redisClient: RedisClient) = {
       for {
           a <- jsonStringF1
           t <- jsonStringF2
       } yield {
           val historyKey = "history." + tableKey
           val anotherKey = "another." + tableKey
   
           val tran = redisClient.transaction()
           tran.zadd(historyKey, (timeStamp, a))
           tran.zadd(anotherKey, (timeStamp, t))
           tran.del(tempKey)
           tran.exec()
       }
   }
   

2. 作为 for 的替代方案，您还可以使用 scala/async ( https://github.com/scala/async ) 并像这样编写代码

   def update(tableKey: String, timeStamp: Long,  jsonStringF1: Future[String], jsonStringF2:Future[String], redisClient: RedisClient) = {
       async {
           val a = await(jsonStringF1)
           val t = await(jsonStringF2)
   
           val historyKey = "history." + tableKey
           val anotherKey = "another." + tableKey
   
           val tran = redisClient.transaction()
           tran.zadd(historyKey, (timeStamp, a))
           tran.zadd(anotherKey, (timeStamp, t))
           tran.del(tempKey)
           tran.exec()
       }
   }
   

这也将是非阻塞的。 异步有一点优势，因为

async blocks are compiled to a single anonymous class, as opposed to a separate anonymous class for each closure required at each generator.