Why does my yarn application not have logs even with logging enabled? - hadoop

Question

I have enabled logs in the xml file: yarn-site.xml, and I restarted yarn by doing:
sudo service hadoop-yarn-resourcemanager restart
sudo service hadoop-yarn-nodemanager restart
I ran my application, and then I see the applicationID in yarn application -list. So, I do this: yarn logs -applicationId <application ID>, and I get the following:
hdfs://<ip address>/var/log/hadoop-yarn/path/to/application/ does not have any log files
Do I need to change some other configuration? Or am I accessing the logs the wrong way?
Thank you.

Answer 1

yarn application -list
will list only the applications that are either in SUBMITTED, ACCEPTED or RUNNING state.
Log aggregation collects each container's logs and moves these logs onto the directory configured in yarn.nodemanager.remote-app-log-dir only after the completion of the application. Refer the description of yarn.log-aggregation-enable property here.
So, the applicationId listed by the command isn't completed yet and the logs are not yet collected. Thus the response when trying to access the logs of a running application
hdfs://<ip address>/var/log/hadoop-yarn/path/to/application/ does not have any log files
You can try the same command yarn logs -applicationId <application ID> to view the logs once the application has completed.
To list all the FINISHED applications, use
yarn application -list -appStates FINISHED
Or to list all the applications
yarn application -list -appStates ALL

Answer 2

Enable Log Aggregation
Log aggregation is enabled in the yarn-site.xml file. The yarn.log-aggregation-enable property enables log aggregation for running applications.
<property>
<name>yarn.log-aggregation-enable</name>
<value>true</value>
</property>

Answer 3

In version 2.3.2 of hadoop and higher you can get log aggregation to occur hourly on running jobs using this configuration in yarn-site.xml:
<property>
<name>yarn.nodemanager.log-aggregation.roll-monitoring-interval-seconds</name>
<value>3600</value>
</property>
See this for further details: https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.3.2/bk_yarn_resource_mgt/content/ref-375ff479-e530-46d8-9f96-8b52dadb5183.1.html

Answer 4

It was probably saved with another appOwner. You can try to specify the application owner in your command:
yarn logs -appOwner .. -application_id ..

Answer 5

ROOT CAUSE: When log aggregation has been enabled each users application logs will, by default, be placed in the directory hdfs:///app-logs//logs/<APPLICATION_ID>. By default only the user that submitted the job and members of the hadoop group will have access to read the log files. In the example directory listing below you can see that the permissions are 770. No access for anyone other than the owner and members of the hadoop group.
[root#mycluster ~]$ hdfs dfs -ls /app-logs
Found 3 items
drwxrwx--- - hive hadoop 0 2017-03-10 15:33 /app-logs/hive
drwxrwx--- - user1 hadoop 0 2017-03-10 15:37 /app-logs/user1
drwxrwx--- - spark hadoop 0 2017-03-10 15:39 /app-logs/spark
SOLUTION: The message above can be deceiving and does not necessarily indicate that log aggregation has not been enabled. To obtain yarn logs for an application the 'yarn logs' command must be executed as the user that submitted the application. In the example below the application was submitted by user1. If we execute the same command as above as the user 'user1' we should get the following output if log aggregation has been enabled.
yarn logs -applicationId application_1473860344791_0001
16/09/19 23:10:33 INFO impl.TimelineClientImpl: Timeline service address: http://mycluster.somedomain.com:8188/ws/v1/timeline/
16/09/19 23:10:33 INFO client.RMProxy: Connecting to ResourceManager at mycluster.somedomain.com/192.168.1.89:8050
16/09/19 23:10:34 INFO zlib.ZlibFactory: Successfully loaded & initialized native-zlib library
16/09/19 23:10:34 INFO compress.CodecPool: Got brand-new decompressor [.deflate]
Container: container_e03_1473860344791_0001_01_000001 on mycluster.somedomain.com_45454
LogType:stderr
Log Upload Time:Wed Sep 14 09:44:15 -0400 2016
LogLength:0
Log Contents:
End of LogType:stderr
REFERENCE: The following document describes how to use log aggregation to collect logs for long-running YARN applications.
http://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.5.0/bk_yarn-resource-management/content/ch_log_a...