线程＃将_ GB的排序数据溢出到磁盘

时间：2016-09-21 20:55:20

标签： scala apache-spark

我尝试编写一个ETL过程，在一个联合之前合并两个数据集我为每个数据集添加一个列，更新的数据集得到2，旧的数据集得到1＆＃39; s，然后如果行具有重复的主键，则删除旧/新列中具有1的行。我曾尝试用多种方式写这篇文章，最近一次是通过以下方式编写：

orderBy(keys, desc(old/new)).dropDuplicates(keys)

但是对于大型数据集，我总是会收到大量减速消息，并显示：

16/09/21 20:31:45 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (0  time so far)
16/09/21 20:32:00 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (1  time so far)
16/09/21 20:32:16 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (2  times so far)
16/09/21 20:32:31 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (3  times so far)
16/09/21 20:32:47 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (4  times so far)
16/09/21 20:33:02 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (5  times so far)
16/09/21 20:33:18 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (6  times so far)
16/09/21 20:33:33 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (7  times so far)
16/09/21 20:33:49 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (8  times so far)
16/09/21 20:34:04 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (9  times so far)
16/09/21 20:34:19 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (10  times so far)
16/09/21 20:34:35 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (11  times so far)
16/09/21 20:34:50 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (12  times so far)
16/09/21 20:35:06 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (13  times so far)
16/09/21 20:35:21 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (14  times so far)
16/09/21 20:35:37 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (15  times so far)
16/09/21 20:35:52 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (16  times so far)
16/09/21 20:36:07 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (17  times so far)
16/09/21 20:36:23 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (18  times so far)
16/09/21 20:36:38 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (19  times so far)
16/09/21 20:36:53 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (20  times so far)
16/09/21 20:37:09 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (21  times so far)
16/09/21 20:37:24 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (22  times so far)
16/09/21 20:37:40 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (23  times so far)
16/09/21 20:37:55 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (24  times so far)
16/09/21 20:38:10 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (25  times so far)
16/09/21 20:38:25 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (26  times so far)
16/09/21 20:38:41 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (27  times so far)
16/09/21 20:38:56 INFO UnsafeExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (28  times so far)
16/09/21 20:39:25 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (0  time so far)
16/09/21 20:39:45 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (1  time so far)
16/09/21 20:40:05 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (2  times so far)
16/09/21 20:40:26 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (3  times so far)
16/09/21 20:40:46 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (4  times so far)
16/09/21 20:41:07 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (5  times so far)
16/09/21 20:41:27 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (6  times so far)
16/09/21 20:41:47 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (7  times so far)
16/09/21 20:42:07 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (8  times so far)
16/09/21 20:42:28 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (9  times so far)
16/09/21 20:42:49 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (10  times so far)
16/09/21 20:43:09 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (11  times so far)
16/09/21 20:43:30 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (12  times so far)
16/09/21 20:43:50 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (13  times so far)
16/09/21 20:44:11 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (14  times so far)
16/09/21 20:44:31 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (15  times so far)
16/09/21 20:44:52 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (16  times so far)
16/09/21 20:45:13 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (17  times so far)
16/09/21 20:45:33 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (18  times so far)
16/09/21 20:45:53 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (19  times so far)
16/09/21 20:46:14 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (20  times so far)
16/09/21 20:46:34 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (21  times so far)
16/09/21 20:46:54 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (22  times so far)
16/09/21 20:47:14 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (23  times so far)
16/09/21 20:47:34 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (24  times so far)
16/09/21 20:47:54 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (25  times so far)
16/09/21 20:48:14 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (26  times so far)
16/09/21 20:48:34 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (27  times so far)
16/09/21 20:48:54 INFO ShuffleExternalSorter: Thread 84 spilling sort data of 3.0 GB to disk (28  times so far)

在检查Spark UI时，只有一个线程加班，其余线程已经完成。
enter image description here
是否有可能在线程之间传播？

1 个答案:

答案 0 :(得分：1)

您通过设计放大与数据偏差相关的任何可能问题的方式来解决此问题。由于您首先按键和指示符变量重新排序数据，因此您首先要对数据进行重新排序，否则可能会创建高度不平衡的分区。之后应用的任何减少都无法弥补这一点。

至少有两种方法可用于实现相同的结果，同时完全受益于地图侧面减少。我在对SPARK DataFrame: select the first row of each group的回答中解释了这两点，以便重申：

  • 您可以使用struct排序来选择每组的最小/最大行数。
  • 您可以使用静态类型Dataset与groupByKey后跟reduceGroups。
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