报错详情：
2020-04-09 22:56:58,827 ERROR [Listener at 0.0.0.0/45871] org.apache.hadoop.mapreduce.v2.app.MRAppMaster: Error starting MRAppMaster org.apache.hadoop.yarn.exceptions.YarnRuntimeException: java.lang.NullPointerException at org.apache.hadoop.mapreduce.v2.app.rm.RMCommunicator.register(RMCommunicator.java:178) at org.apache.hadoop.mapreduce.v2.app.rm.RMCommunicator.serviceStart(RMCommunicator.java:122) at org.apache.hadoop.mapreduce.v2.app.rm.RMContainerAllocator.serviceStart(RMContainerAllocator.java:280) at org.apache.hadoop.service.AbstractService.start(AbstractService.java:194) at org.apache.hadoop.mapreduce.v2.app.MRAppMaster$ContainerAllocatorRouter.serviceStart(MRAppMaster.java:979) at org.apache.hadoop.service.AbstractService.start(AbstractService.java:194) at org.apache.hadoop.service.CompositeService.serviceStart(CompositeService.java:121) at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.serviceStart(MRAppMaster.java:1293) at org.apache.hadoop.service.AbstractService.start(AbstractService.java:194) at org.apache.hadoop.mapreduce.v2.app.MRAppMaster$6.run(MRAppMaster.java:1761) 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:1730) at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.initAndStartAppMaster(MRAppMaster.java:1757) at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.main(MRAppMaster.java:1691) Caused by: java.lang.NullPointerException at org.apache.hadoop.mapreduce.v2.app.client.MRClientService.getHttpPort(MRClientService.java:177) at org.apache.hadoop.mapreduce.v2.app.rm.RMCommunicator.register(RMCommunicator.java:159) ... 14 more 2020-04-09 22:56:58,818 INFO [TaskHeartbeatHandler PingChecker] org.apache.hadoop.mapreduce.v2.app.TaskHeartbeatHandler: TaskHeartbeatHandler thread interrupted 2020-04-09 22:56:58,819 INFO [Ping Checker] org.apache.hadoop.yarn.util.AbstractLivelinessMonitor: TaskAttemptFinishingMonitor thread interrupted
阅读源代码，会发现这是由于org.apache.hadoop.yarn.server.webproxy.amfilter.AmFilterInitializer.java这个类中的一段代码引起的，涉及的代码如下：
if (rmIds != null) {
List<String> urls = new ArrayList<>();
for (String rmId : rmIds) {
String url = getUrlByRmId(yarnConf, rmId);
// urls.add(url); // 注释掉这端代码，修改为下面的if语句判断是否为null
if (url != null) {
urls.add(url);
}
}
if (!urls.isEmpty()) {
params.put(RM_HA_URLS, StringUtils.join(",", urls));
}
}
这与yarn-site.xml配置HA的兼容性有关，取决于 yarn.resourcemanager.webapp.address 和 yarn.resourcemanager.webapp.https.address 是否为空。
修改源码的方法：
1、首先将hadoop-yarn-server-web-proxy-3.2.1.jar从服务器上拿下来。
2、使用JD-GUI打开，复制org.apache.hadoop.yarn.server.webproxy.amfilter.AmFilterInitializer.java类中代码；
3、在eclipse新建一个工程，然后新建一个类插入复制的代码，并进行修改。
4、有报错的话就build class，把本地的hadoop相关的包导入
5、将该工程导出为jar包。
6、分别打开hadoop-yarn-server-web-proxy-3.2.1.jar 和刚导出的jar包用解压软件打开，替换原来的org.apache.hadoop.yarn.server.webproxy.amfilter.AmFilterInitializer.class文件。
修改完后替换原来的jar包，重启hdfs和yarn.job运行成功！
Hive进行数据统计时报错：org.apache.hadoop.mapreduce.v2.app.MRAppMaster: Error starting MRAppMaster