背景
目前借助于 Azkaban 进行大数据相关任务调度。任务执行失败会收到响应的告警。本次失败登录 Azkaban 错误日志分析，核心错误 Job failed as tasks failed. failedMaps:1 failedReduces:0
但是Azkaban 页面错误信息显示不是非常详细。没有看到失败的具体原因是什么。同步收到开发反馈，对应的业务数据相比之前少了一半。
任务执行失败，开发反馈有数据，但是数据相比之前少了一半。
问题分析
1、找到对应azkaban任务脚本，看到是利用 sqoop export 从hive从导出数据到mysql数据库表
2、查看 mysql 库表记录，只有100条，但是正常情况应该是200条记录
3、查看hive中对应的表，显示结果是200条。所以源头数据应该是没有问题的。
4、排查相关错误日志未发现有用信息。因为200条记录，导入了100条，那么是不是第101条数据有问题呢？
5、在hive执行分页查询 select * from xxx where dt='2022-09-15' limit 100, 1; 刚好看到第101条记录的部分字段合并在了一起，因为是0和Null合并，很明显
6、这个时候怀疑是数据源有问题，两个字段显示在一起 导致实际hive表中的字段个数和mysql表中的字段个数不一致导致的
7、又是各种找日志分析，未发现到有用信息，在另外一个主机上用普通用户登录hive查询的时候虽然有告警信息，但是第101行记录的显示确实正常的，没有出现字段显示在一起 的问题，那么就能真正的排除数据源的问题
8、这个时候暂停转而去了解 sqoop 的用法，看是否哪里用的不对，是在不同的用户下sqoop查询字段获取的问题，做实验也未验证到结果
9、然后再了解sqoop的过程中，get到sqoop export也是把任务转化成Hadoop的mapreduct job去执行的。其实在azkaban的错误日志中就有显示INFO mapreduce.Job: Job job_1659629210017_4904 failed with state FAILED due to: Task failed task_1659629210017_4904_m_000000 只是当初没有注意到罢了，部分详细错误日志详见文末
10、了解大数据的都知道，mapreduct job 最终的调度和任务执行都是通过Yarn来进行的，在Hadoop job页面可以找到 报错的JOBID，进而可以找到该任务是调度到那个 NodeManager 去执行的，
11、登录执行的NodeManager 通过如下命令去获取详细的执行日志
yarn logs -applicationId application_1659629210017_4904
看到有错误信息
2022-10-08 16:34:58,417 ERROR [Thread-11] org.apache.sqoop.mapreduce.AsyncSqlOutputFormat: Got exception in update thread: com.mysql.jdbc.MysqlDataTruncation: Data truncation: Data too long for column 'receiveDiscordIds' at row 1
目前数据库中该字段是text类型，长度不够，那就修改为 mediumtext类型 ，清理掉mysql中异常数据，重新跑任务成功，数据200条
总结
1、azkaban 任务执行失败，首先看azkaban 提供的错误信息，一般在脚本中会在关键位置输出日志。有助于排查问题
2、如果azkaban 没有找到问题根源，大数据任务最终都是通过Yarn调用和执行的，可以通过Hadoop Job 管理页面找到调度的节点
3、在Yarn节点上执行 yarn logs -applicationId application_id 可以找到更加详细的执行过程中的日志
扩展 Yarn 架构
Yarn 四大组件的介绍
ResourceManager：
1、处理客户端请求
2、启动/监控ApplicationMaster
3、监控NodeManager
4、资源分配与调度
APPlicationMaster：
1、程序切分
2、为应用程序申请资源，并分配任务
3、任务监控与容错
NodeManager：
1、单个节点上资源管理
2、处理来自ResourceManager的命令
3、处理来自ApplicationMaster的命令
Container：
对任务运行环境的抽象，封装了CPU、内存等多维资源以及环境变量、启动命令等任务运行相关信息’
附加
部分失败任务的日志
15-09-2022 09:22:31 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:31 INFO mapreduce.Job: map 0% reduce 0%
15-09-2022 09:22:43 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:43 INFO mapreduce.Job: map 100% reduce 0%
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 INFO mapreduce.Job: Job job_1659629210017_4904 failed with state FAILED due to: Task failed task_1659629210017_4904_m_000000
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Job failed as tasks failed. failedMaps:1 failedReduces:0
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO -
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 INFO mapreduce.Job: Counters: 8
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Job Counters
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Failed map tasks=1
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Launched map tasks=1
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Rack-local map tasks=1
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Total time spent by all maps in occupied slots (ms)=469680
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Total time spent by all reduces in occupied slots (ms)=0
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Total time spent by all map tasks (ms)=9785
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Total vcore-milliseconds taken by all map tasks=9785
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Total megabyte-milliseconds taken by all map tasks=480952320
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 WARN mapreduce.Counters: Group FileSystemCounters is deprecated. Use org.apache.hadoop.mapreduce.FileSystemCounter instead
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 INFO mapreduce.ExportJobBase: Transferred 0 bytes in 46.0112 seconds (0 bytes/sec)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 WARN mapreduce.Counters: Group org.apache.hadoop.mapred.Task$Counter is deprecated. Use org.apache.hadoop.mapreduce.TaskCounter instead
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 INFO mapreduce.ExportJobBase: Exported 0 records.
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 ERROR mapreduce.ExportJobBase: Export job failed!
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - 22/09/15 09:22:44 ERROR tool.ExportTool: Error during export:
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - Export job failed!
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.mapreduce.ExportJobBase.runExport(ExportJobBase.java:445)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.manager.SqlManager.exportTable(SqlManager.java:931)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.tool.ExportTool.exportTable(ExportTool.java:80)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.tool.ExportTool.run(ExportTool.java:99)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.Sqoop.run(Sqoop.java:147)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:183)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.Sqoop.runTool(Sqoop.java:234)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.Sqoop.runTool(Sqoop.java:243)
15-09-2022 09:22:44 CST export_dmr_deceitful_delivery INFO - at org.apache.sqoop.Sqoop.main(Sqoop.java:252)
参考地址：
https://blog.csdn.net/NDF923/article/details/122067125
https://blog.csdn.net/qq_43842093/article/details/122401599