YARN 应用级日志配置：深入解析 Hadoop 日志管理
Hadoop 作为大数据处理框架，其核心组件 YARN（Yet Another Resource Negotiator）负责资源管理和作业调度。在 YARN 运行过程中，会产生大量的应用级日志，这些日志对于监控、调试和优化 YARN 应用至关重要。本文将围绕 YARN 应用级日志的配置，从日志级别和输出路径两个方面进行深入解析。
YARN 应用级日志概述
YARN 应用级日志主要记录了 YARN 应用在运行过程中的各种信息，包括资源分配、任务执行、错误处理等。这些日志对于开发者、运维人员来说，是了解应用运行状态、排查问题的重要依据。
日志级别
YARN 应用级日志的级别包括：DEBUG、INFO、WARN、ERROR 和 FATAL。不同级别的日志记录了不同粒度的信息，以下是各个级别的简要说明：
- DEBUG：记录最详细的日志信息，用于调试程序。
- INFO：记录一般性的信息，如任务启动、结束等。
- WARN：记录警告信息，如资源不足、任务失败等。
- ERROR：记录错误信息，如任务执行失败、系统异常等。
- FATAL：记录致命错误信息，如系统崩溃、无法恢复的错误等。
日志输出路径
YARN 应用级日志的输出路径通常包括以下几种：
- 应用日志目录：每个 YARN 应用都会在 HDFS 上生成一个日志目录，用于存储该应用的所有日志文件。
- YARN 日志目录：YARN 集群中所有应用的日志文件都会存储在 YARN 日志目录下。
- HDFS 日志目录：部分 YARN 应用会将日志输出到 HDFS 日志目录。
YARN 应用级日志配置
1. 日志级别配置
在 YARN 应用中，可以通过以下几种方式配置日志级别：
1.1 配置文件
在 YARN 应用启动时，可以通过配置文件设置日志级别。以 Java 应用为例，可以在 `yarn-site.xml` 文件中添加以下配置：
```xml
<property>
<name>yarn.log-aggregation-enable</name>
<value>true</value>
</property>
<property>
<name>yarn.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation-enable</name>
<value>true</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.retain-seconds</name>
<value>604800</value>
</property>
<property>
<name>yarn.nodemanager.log-aggregation.max-aggregation bytes</name>
<value>1073741824</value>
</property>
<property>
<name>y
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