[jira] [Assigned] (SPARK-31632) The ApplicationInfo in KVStore may be accessed before it's prepared

["Apache Spark (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-31632?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-31632:
------------------------------------

    Assignee:     (was: Apache Spark)

> The ApplicationInfo in KVStore may be accessed before it's prepared
> -------------------------------------------------------------------
>
>                 Key: SPARK-31632
>                 URL: https://issues.apache.org/jira/browse/SPARK-31632
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core, Web UI
>    Affects Versions: 3.0.0
>            Reporter: Xingcan Cui
>            Priority: Minor
>
> While starting some local tests, I occasionally encountered the following exceptions for Web UI.
> {noformat}
> 23:00:29.845 WARN org.eclipse.jetty.server.HttpChannel: /jobs/
>  java.util.NoSuchElementException
>  at java.util.Collections$EmptyIterator.next(Collections.java:4191)
>  at org.apache.spark.util.kvstore.InMemoryStore$InMemoryIterator.next(InMemoryStore.java:467)
>  at org.apache.spark.status.AppStatusStore.applicationInfo(AppStatusStore.scala:39)
>  at org.apache.spark.ui.jobs.AllJobsPage.render(AllJobsPage.scala:266)
>  at org.apache.spark.ui.WebUI.$anonfun$attachPage$1(WebUI.scala:89)
>  at org.apache.spark.ui.JettyUtils$$anon$1.doGet(JettyUtils.scala:80)
>  at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
>  at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
>  at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:873)
>  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1623)
>  at org.apache.spark.ui.HttpSecurityFilter.doFilter(HttpSecurityFilter.scala:95)
>  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
>  at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
>  at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
>  at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
>  at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
>  at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
>  at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
>  at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
>  at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
>  at org.eclipse.jetty.server.handler.gzip.GzipHandler.handle(GzipHandler.java:753)
>  at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220)
>  at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
>  at org.eclipse.jetty.server.Server.handle(Server.java:505)
>  at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370)
>  at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267)
>  at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
>  at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
>  at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117)
>  at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:698)
>  at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:804)
>  at java.lang.Thread.run(Thread.java:748){noformat}
> *Reason*
>  That is because {{AppStatusStore.applicationInfo()}} accesses an empty view (iterator) returned by {{InMemoryStore}}.
> AppStatusStore
> {code:java}
> def applicationInfo(): v1.ApplicationInfo = {
>     store.view(classOf[ApplicationInfoWrapper]).max(1).iterator().next().info
> }
> {code}
> InMemoryStore
> {code:java}
> public <T> KVStoreView<T> view(Class<T> type){
>     InstanceList<T> list = inMemoryLists.get(type);
>     return list != null ? list.view() : emptyView();
>  }
> {code}
> During the initialization of {{SparkContext}}, it first starts the Web UI (SparkContext: L475 _ui.foreach(_.bind())) and then setup the {{LiveListenerBus}} thread (SparkContext: L608 {{setupAndStartListenerBus()}}) for dispatching the {{SparkListenerApplicationStart}} event (which will trigger writing the requested {{ApplicationInfo}} to {{InMemoryStore}}).
> *Solution*
>  Since the {{applicationInfo()}} method is expected to always return a valid {{ApplicationInfo}}, maybe we can add a while-loop-check here to guarantee the availability of {{ApplicationInfo}}.
> {code:java}
> def applicationInfo(): v1.ApplicationInfo = {
>  var iterator = store.view(classOf[ApplicationInfoWrapper]).max(1).iterator()
>  while (!iterator.hasNext){ 
>     Thread.sleep(20) 
>     iterator = store.view(classOf[ApplicationInfoWrapper]).max(1).iterator() 
>   }
>   iterator.next().info
> }
> {code}



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