ENABLING DEBUG LOGGING – EMR MASTER GUIDE

Written by mannem on . Posted in AWS BIG DATA, EMR || Elastic Map Reduce

Contains different configurations and procedures to enable logging on different daemons on AWS EMR cluster.
[Please contribute to this article to add additional ways to enable logging]

HBASE on S3 :

This will enable calls made from EMRFS from HBASE.

Important to troubleshoot S3 consistency issues and failures for HBASE on S3 cluster.

Enabling DEBUG on Hive Metastore daemon (its Datastore) on EMR :

or

Logs at /var/log/hive/user/hive/hive.log

HUE:

use_get_log_api=true in the beeswaxsection of the hue.ini configuration file.

Hadoop and MR :

Enable GC verbose on Hive Server 2 JVM:

WIRE OR DEBUG logging on EMR to check calls to S3 and DDB for DynamoDb connector library :

Paste the following on log4j configurations of Hadoop / hive / spark etc.

/etc/hadoop/conf/log4j.properties
/etc/hadoop/conf/container-log4j.properties
/etc/hive/conf/hive-log4j2.properties
/etc/spark/conf/..

https://github.com/awslabs/emr-dynamodb-connector/blob/master/emr-dynamodb-hive/src/test/resources/log4j.properties

Debug on S3 Calls from EMR HIVE :

These metrics can be obtained from the hive.log when enabling debug logging in aws-java-sdk. To enable this logging, add the following line to '/etc/hive/conf/hive-log4j.properties'. The Configuration API can be used as well.

Enable DEBUG logging for Http Connection pool:

(from spark) by adding the following to /etc/spark/conf/log4j.properties

*Tez overwrites the loglevel options we have passed. Please see the related items.*

Enabling Debug on Hadoop log to log calls by EMRFS :

/etc/hadoop/conf/log4j.properties

You can use same logging config for other Application like spark/hbase using respective log4j config files as appropriate. You can also use EMR log4j configuration classification like hadoop-log4j or spark-log4j to set those config’s while starting EMR cluster.(see below for sample JSON for configuration API)

https://docs.aws.amazon.com/emr/latest/ReleaseGuide/emr-configure-apps.html

DEBUG on EMR Logpusher Logs :

Edit this file on Master / Slave’s manually and restart Logpusher.

/etc/logpusher/logpusher-log4j.properties

(Might need to stop Service-nanny before stopping Logpusher, to properly stop/start Logpusher)

DEBUG on Spark classes :

Use the following EMR config to set DEBUG level for relevant class files.

DEBUG using spark shell:

Execute the following commands after invoking spark-shell to enable DEBUG logging on respective spark classes like Memstore. You can use the same if you want to reduce the amount of logging from INFO (which is default coming from log4j.properties in the spark conf ) to ERROR.

EMRFS CLI command like EMRFS SYNC :

/etc/hadoop/conf/log4j.properties

Logs will be on the console out. We might need to redirect to a File or do both.

Enable Debug on Boto3 client :

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