Set log level of namenode

The below steps describe how to change the Namenode log level while logged on as hdfs with the below steps, without the need to restart the namenode

Get the current log level

$ hadoop daemonlog -getlevel {namenode_host}:50070BlockStateChange

Desired Output

Connecting to http://{namenode_host}:50070/logLevel?log=BlockStateChange
SubmittedLogName:BlockStateChange
LogClass: org.apache.commons.logging.impl.Log4J
LoggerEffectiveLevel: INFO

Change to DEBUG

$ hadoop daemonlog -setlevel {namenode_host}:50070BlockStateChange DEBUG

Desired Output

Connecting to http://{namenode_host}:50070/logLevel?log=BlockStateChange&level=DEBUG
SubmittedLogName:BlockStateChange
LogClass: org.apache.commons.logging.impl.Log4J
LoggerSubmittedLevel: DEBUG
SettingLevel to DEBUG ...
EffectiveLevel: DEBUG

Validate DEBUG mode

$ hadoop daemonlog -getlevel {namenode_host}:50070BlockStateChange

Desired Output

Connecting to http://{namenode_host}:50070/logLevel?log=BlockStateChange
SubmittedLogName:BlockStateChange
LogClass: org.apache.commons.logging.impl.Log4J
LoggerEffectiveLevel: DEBUG

You should be able to notice the logging level in namenode.log has been updated, without restarting the service. After finishing your diagnostics you can reset the logging level back to INFO

Reset to INFO

$ hadoop daemonlog -setlevel {namenode_host}:50070BlockStateChange INFO

Desired Output

Connecting to http://{namenode_host}:50070/logLevel?log=BlockStateChange&level=INFO
SubmittedLogName:BlockStateChange
LogClass: org.apache.commons.logging.impl.Log4J
LoggerSubmittedLevel: INFO
SettingLevel to INFO ...
EffectiveLevel: INFO

Validate INFO

$ hadoop daemonlog -getlevel {namenode_host}:50070BlockStateChange

Output

Connecting to http://{namenode_host}:50070/logLevel?log=BlockStateChange
SubmittedLogName:BlockStateChange
LogClass: org.apache.commons.logging.impl.Log4J
LoggerEffectiveLevel: INFO

Happy hadooping !!!!