flink1.12.x Table API 和 SQL：UDF用户自定义函数-ScalarFunction标量函数
flink1.12.x Table API 和 SQL：UDF用户自定义函数介绍
hadoop3.x MapReduce-reduce()方法中，values迭代时，key的值不断变化分析及源码
hadoop3.x MapReduce-统计学生的平均分数
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
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
hadoop hdfs关闭权限管理
hadoop3.x /tmp 需要 777 权限
hadoop3.x yarn 调度策略：Fair Scheduler（公平调度）根据linux登录名提交到队列