为什么我的地图缩小作业是按顺序运行的？

Question

我有一个4节点的集群和总共96GB的内存。

我已将输入分为100个文件，并将作业设置为有100个映射器。从日志看来，Mappers依次运行。

[2014/10/08 15:22:36] INFO: Total input paths to process : 100 
[2014/10/08 15:22:36] INFO: number of splits:100 
[2014/10/08 15:22:36] INFO: Starting task: attempt_local1244628585_0001_m_000000_0 
[2014/10/08 15:22:36] INFO: Submitting tokens for job: job_local1244628585_0001 
[2014/10/08 15:22:36] INFO: Processing split: hdfs://.../input/in10:0+2 
[2014/10/08 15:22:38] INFO: Task:attempt_local1244628585_0001_m_000000_0 is done. And is in the process of committing 
[2014/10/08 15:22:38] INFO: Task attempt_local1244628585_0001_m_000000_0 is allowed to commit now 
[2014/10/08 15:22:38] INFO: Saved output of task 'attempt_local1244628585_0001_m_000000_0' to hdfs://.../output/_temporary/0/task_local1244628585_0001_m_000000 
[2014/10/08 15:22:38] INFO: hdfs://.../input/in10:0+2 
[2014/10/08 15:22:38] INFO: Task 'attempt_local1244628585_0001_m_000000_0' done. 
[2014/10/08 15:22:38] INFO: Finishing task: attempt_local1244628585_0001_m_000000_0 
[2014/10/08 15:22:38] INFO: Starting task: attempt_local1244628585_0001_m_000001_0 

....

和和。 基本上，它在开始另一个任务之前完成一项任务。

Answer 1

您在本地模式下运行：

[2014/10/08 15:22:36] INFO: Starting task: attempt_**local**1244628585_0001_m_000000_0 

根据您的Hadoop版本，您可能需要配置JobTracker的地址，或该地址的ResourceManager。