Chao Sun created HDFS-14110:
-------------------------------

             Summary: NPE when serving http requests while NameNode is starting 
up
                 Key: HDFS-14110
                 URL: https://issues.apache.org/jira/browse/HDFS-14110
             Project: Hadoop HDFS
          Issue Type: Improvement
    Affects Versions: 2.8.2
            Reporter: Chao Sun
            Assignee: Chao Sun


In 2.8.2 we saw this exception when a security-enabled NameNode is still 
loading edits:
{code:java}
2018-11-28 00:21:02,909 INFO org.apache.hadoop.util.JvmPauseMonitor: Detected 
pause in JVM or host machine (eg GC): pause of approximately 2068ms GC pool 
'ParNew' had collection(s): count=1 time=2325ms 2018-11-28 00:21:05,768 WARN 
org.apache.hadoop.hdfs.web.resources.ExceptionHandler: INTERNAL_SERVER_ERROR 
java.lang.NullPointerException at 
org.apache.hadoop.hdfs.server.common.JspHelper.getTokenUGI(JspHelper.java:283) 
at org.apache.hadoop.hdfs.server.common.JspHelper.getUGI(JspHelper.java:226) at 
org.apache.hadoop.hdfs.web.resources.UserProvider.getValue(UserProvider.java:54)
 at 
org.apache.hadoop.hdfs.web.resources.UserProvider.getValue(UserProvider.java:42)
 at 
com.sun.jersey.server.impl.inject.InjectableValuesProvider.getInjectableValues(InjectableValuesProvider.java:46)
 at 
com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$EntityParamInInvoker.getParams(AbstractResourceMethodDispatchProvider.java:153)
 at 
com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:203)
 at 
com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
 at 
com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
 at 
com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
 at 
com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
 at 
com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
 at 
com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
 at 
com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
 at 
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
 at 
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
 at 
com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
 at 
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
 at 
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:820) at 
org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1221)
 at org.apache.hadoop.hdfs.web.AuthFilter.doFilter(AuthFilter.java:87) at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
 at 
org.apache.hadoop.http.HttpServer2$QuotingInputFilter.doFilter(HttpServer2.java:1353)
 at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
 at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45) at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
 at org.apache.hadoop.http.NoCacheFilter.doFilter(NoCacheFilter.java:45) at 
org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
 at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399) at 
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at 
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at 
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766) at 
org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450) at 
org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
 at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at 
org.mortbay.jetty.Server.handle(Server.java:326) at 
org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at 
org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
 at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549) at 
org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212) at 
org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at 
org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410) at 
org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
{code}
Looking at the code, this is where the NPE happened (the line with 
{{verifyToken}}):
{code:java}
    if (context != null) {
      final NameNode nn = NameNodeHttpServer.getNameNodeFromContext(context);
      if (nn != null) {
        // Verify the token.
        nn.getNamesystem().verifyToken(id, token.getPassword());
      }
    }
{code}
In {{NameNode::initialize}}, the namesystem is initialized _after_ the http 
server is started, and usually it takes a while before fsimage is loaded and 
{{namesystem}} becomes non-null:
{code:java}
    if (NamenodeRole.NAMENODE == role) {
      startHttpServer(conf);
    }

    loadNamesystem(conf);
{code}
Perhaps it should throw a proper exception instead of failing with NPE.



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