一：类类型使用不一致（mapper和reduce）
20/01/13 16:03:42 INFO conf.Configuration: found resource resource-types.xml at file:/tmp/hadoop-unjar5833957221661452217/resource-types.xml
20/01/13 16:03:42 INFO resource.ResourceUtils: Adding resource type - name = rm1, units = G, type = COUNTABLE
20/01/13 16:03:42 INFO resource.ResourceUtils: Adding resource type - name = rm2, units = , type = COUNTABLE
20/01/13 16:03:42 INFO resource.ResourceUtils: Adding resource type - name = memory-mb, units = Mi, type = COUNTABLE
20/01/13 16:03:42 INFO resource.ResourceUtils: Adding resource type - name = vcores, units = , type = COUNTABLE
20/01/13 16:03:43 INFO impl.YarnClientImpl: Submitted application application_1578714121919_0001
20/01/13 16:03:43 INFO mapreduce.Job: The url to track the job: http://node04:8088/proxy/application_1578714121919_0001/
20/01/13 16:03:43 INFO mapreduce.Job: Running job: job_1578714121919_0001
20/01/13 16:03:51 INFO mapreduce.Job: Job job_1578714121919_0001 running in uber mode : false
20/01/13 16:03:51 INFO mapreduce.Job: map 0% reduce 0%
20/01/13 16:03:57 INFO mapreduce.Job: map 100% reduce 0%
20/01/13 16:04:01 INFO mapreduce.Job: Task Id : attempt_1578714121919_0001_r_000000_0, Status : FAILED
Error: java.lang.ClassCastException: org.apache.hadoop.io.Text cannot be cast to org.apache.hadoop.util.bloom.Key
at com.ideatech.hadoop.mapreduce.MyReduce.reduce(MyReduce.java:14)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:627)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:389)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:177)
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:1893)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:171)
20/01/13 16:04:06 INFO mapreduce.Job: Task Id : attempt_1578714121919_0001_r_000000_1, Status : FAILED
这是因为mapper和reduce的继承类，使用的T参数不一致造成，比如，map里面使用Text ，reduce里面使用Key，就会出现类型强转异常
二：2.10.0版本缺少配置文件（不同于低版本2.x）
2.10.0需要配置相关的参数，yarn资源管理的相关参数，较之2.x低版本有较多区别
三：AM资源分配问题，始终在等待分配资源
参考文章：www.cnblogs.com/yjt1993/p/9…
四：缺少resource-types.xml 配置文件，低版本2.x不需要，高版本2.x和3.x需要，具体从哪个版本开始，未曾查明（参考如下）
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
<property>
<name>yarn.resource-types</name>
<value>rm1, rm2</value>
</property>
<property>
<name>yarn.resource-types.rm1.units</name>
<value>G</value>
</property>
<property>
<!-- Maximum resources to allocate to application masters
If this is too high application masters can crowd out actual work -->
<name>yarn.scheduler.capacity.maximum-am-resource-percent</name>
<value>0.6</value>
</property>
<!-- <property>-->
<!-- <name>yarn.scheduler.minimum-allocation-mb</name>-->
<!-- <value>1</value>-->
<!-- </property>-->
<!-- <property>-->
<!-- <name>yarn.scheduler.maximum-allocation-mb</name>-->
<!-- <value>1</value>-->
<!-- </property>-->
<!-- <property>-->
<!-- <name>yarn.resource-types.rm2.minimum</name>-->
<!-- <value>1</value>-->
<!-- </property>-->
<!-- <property>-->
<!-- <name>yarn.resource-types.rm2.maximum</name>-->
<!-- <value>1</value>-->
<!-- </property>-->
</configuration>
五：yarn资源管理分配未曾成功启动（下图是成功启动后的显示——HA模式）
*：注意 Memory Total 和 Apps Completed ，VCores Used
配置文件未正确配置
- 总结：Hadoop系列，1.x，2.x和3.x等几个大版本差异较大，若要进行操作，最好使用2.x偏中版本，3.x偏低，比如2.6 ，2.7之类，或者3.2或3.1（时间：20200113）。最好三阶段的异动和变革史能探索下。
