[jira] [Created] (MAPREDUCE-5751) MR app master fails to start in some cases if mapreduce.job.classloader is true

["Sangjin Lee (JIRA)" <ji...@apache.org>]

Sangjin Lee created MAPREDUCE-5751:
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             Summary: MR app master fails to start in some cases if mapreduce.job.classloader is true
                 Key: MAPREDUCE-5751
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5751
             Project: Hadoop Map/Reduce
          Issue Type: Bug
    Affects Versions: 2.2.0
            Reporter: Sangjin Lee
            Assignee: Sangjin Lee


If mapreduce.job.classloader is set to true, and the MR client includes a jetty jar in its libjars or job jar, the MR app master fails to start. A typical stack trace we get is as follows:

{noformat}
java.lang.ClassCastException: org.mortbay.jetty.webapp.WebInfConfiguration cannot be cast to org.mortbay.jetty.webapp.Configuration
	at org.mortbay.jetty.webapp.WebAppContext.loadConfigurations(WebAppContext.java:890)
	at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:462)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:152)
	at org.mortbay.jetty.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:156)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
	at org.mortbay.jetty.Server.doStart(Server.java:224)
	at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
	at org.apache.hadoop.http.HttpServer.start(HttpServer.java:676)
	at org.apache.hadoop.yarn.webapp.WebApps$Builder.start(WebApps.java:208)
	at org.apache.hadoop.mapreduce.v2.app.client.MRClientService.start(MRClientService.java:151)
	at org.apache.hadoop.yarn.service.CompositeService.start(CompositeService.java:68)
	at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.start(MRAppMaster.java:1040)
	at org.apache.hadoop.mapreduce.v2.app.MRAppMaster$1.run(MRAppMaster.java:1307)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1478)
	at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.initAndStartAppMaster(MRAppMaster.java:1303)
	at org.apache.hadoop.mapreduce.v2.app.MRAppMaster.main(MRAppMaster.java:1259)
{noformat}

This happens because as part of the MR app master start the jetty classes are loaded normally through the app classloader, but WebAppContext tries to load the specific Configuration class via the thread context classloader (which had been set to the user job classloader).



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