java.io.IOException：所有收集器的初始化失败。最后一个收集器的错误是：null

Question

我是MapReduce的新手，我试图找到一个问题的解决方案。我试图链接两个map reduce作业。第一个作业正在执行，但是在第二个作业中我遇到了如下错误

     INFO mapreduce.Job: Task Id : attempt_1445271708293_0055_m_000000_1, Status : FAILED
Error: java.io.IOException: Initialization of all the collectors failed.              Error in last collector was :null
    at org.apache.hadoop.mapred.MapTask.createSortingCollector(MapTask.java:414)
    at org.apache.hadoop.mapred.MapTask.access$100(MapTask.java:81)
    at org.apache.hadoop.mapred.MapTask$NewOutputCollector.<init>(MapTask.java:698)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:770)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
    at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:164)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:422)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
    at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.NullPointerException
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.init(MapTask.java:1011)
    at org.apache.hadoop.mapred.MapTask.createSortingCollector(MapTask.java:402)
    ... 9 more

Answer 1

当map任务的输出类型与reduce任务的输入类型不匹配时，我遇到了同样的错误。

映射器中的最后两个参数应与减速器中的前两个参数具有相同的类型。

public class ByteCalculationMapper extends Mapper<LongWritable, Text, Text, IntWritable> {

public class ByteCalculationReducer extends Reducer<Text, IntWritable, Text, Text> {