hadoop3.x MapReduce Combiner作用
hadoop3.x MapReduce-排序
hadoop3.x MapReduce-统计学生的平均分数
hadoop3.x yarn 调度策略：Fair Scheduler（公平调度）根据linux登录名提交到队列
hadoop3.x yarn 调度策略：Fair Scheduler（公平调度）根据linux登录名提交到队列
hadoop3.x MapReduce序列化案例-统计充电桩充电量、充电时长、充电次数
Container exited with a non-zero exit code 1. Error file: prelaunch.err. Last 4096 bytes of prelaunch.err : Last 4096 bytes of stderr : log4j:WARN No appenders could be found for logger
hadoop3.x MapReduce序列化机制-自定义序列化类（Writable、WritableComparable）
Failed to submit application_to YARN : User dev cannot submit applications to queue root.dev(requested queuename is default)
org.apache.hadoop.security.AccessControlException: Permission denied: user=dev, access=EXECUTE, inode="/tmp":root:supergroup:drwx