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https://issues.apache.org/jira/browse/YARN-4709?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Varun Vasudev resolved YARN-4709.
---------------------------------
Resolution: Fixed
> NMWebServices produces incorrect JSON for containers
> ----------------------------------------------------
>
> Key: YARN-4709
> URL: https://issues.apache.org/jira/browse/YARN-4709
> Project: Hadoop YARN
> Issue Type: Bug
> Reporter: Varun Saxena
> Assignee: Varun Saxena
> Priority: Critical
> Fix For: 2.8.0
>
> Attachments: YARN-4709.01.patch, YARN-4709.02.patch
>
>
> Following exception is thrown when we run below command.
> {panel}
> root@varun-Inspiron-5558:/opt1/hadoop3/bin# ./yarn logs -applicationId
> application_1455999168135_0002 -am ALL -logFiles ALL
> Container: container_e31_1455999168135_0002_01_000001
> =======================================================
> {color:red}LogType:syslogstderrstdout
> Log Upload Time:Sun Feb 21 01:44:55 +0530 2016
> Log Contents:
> java.lang.Exception: Cannot find this log on the local disk.
> End of LogType:syslogstderrstdout{color}
> LogType:syslog
> Log Upload Time:Sun Feb 21 01:44:55 +0530 2016
> Log Contents:
> 2016-02-21 01:44:49,565 INFO \[main\]
> org.apache.hadoop.mapreduce.v2.app.MRAppMaster: Created MRAppMaster for
> application appattempt_1455999168135_0002_000001
> 2016-02-21 01:44:49,914 INFO \[main\]
> org.apache.hadoop.mapreduce.v2.app.MRAppMaster:
> /************************************************************
> {panel}
> This is because we annotate containerLogFiles list with XmlElementWrapper
> which generates XML output as under. And when we read this XML at client
> side, reading the value associated with containerLogFiles also leads to one
> value being syslogstderrstdout because both parent and child tags are same.
> This leads to the exception.
> {noformat}
> <containerLogFiles>
> <containerLogFiles>syslog</containerLogFiles>
> <containerLogFiles>stderr</containerLogFiles>
> <containerLogFiles>stdout</containerLogFiles>
> </containerLogFiles>
> {noformat}
> Moreover, as we use XMLElementWrapper, the JSON generated is as under. This
> JSON cannot be properly parsed by JSON parser(as a list). This is because
> child containerLogsFiles entries are treated as a key-value pair(map) and
> hence only last entry i.e. stdout is picked up. This was found while working
> on YARN-4517. This makes output unusable.
> This will be an issue for 2 REST endpoints i.e. {{/ws/v1/node/containers}}
> and {{/ws/v1/node/containers/\{\{containerId\}\}}}
> {noformat}
> "containerLogFiles":[
> {
> "containerLogFiles":"syslog",
> "containerLogFiles":"stderr",
> "containerLogFiles":"stdout"
> }
> ]
> {noformat}
> Ideally the JSON output should be as under.
> {noformat}
> "containerLogFiles":["syslog","stderr","stdout"]
> {noformat}
> We can indicate in the JAXB context to ignore the outer wrapper while
> marshalling to JSON. But this can only be done at class level. If we do so
> for ContainerInfo, it would break backward compatibility.
> Hence, to fix it we can remove XmlElementWrapper annotation for
> containerLogFiles list.
> Another solution would be to wrap the list inside another class.
> But going with former as of now as we do not specify XmlElementWrapper for
> lists at most of the places in our code.
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