warning due to threading in Spark

[peiworld]

WARN FileSystem: exception in the cleaner thread but it will continue to run
java.lang.InterruptedException
at java.lang.Object.wait(Native Method)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
at org.apache.hadoop.fs.FileSystem$Statistics$StatisticsDataReferenceCleaner.run(FileSystem.java:3063)
at java.lang.Thread.run(Thread.java:745)
[WARNING] thread Thread[org.apache.hadoop.fs.FileSystem$Statistics$StatisticsDataReferenceCleaner,5,spiritlab.sparkfhe.example.basic.DotProductExample] was interrupted but is still alive after waiting at least 12884msecs
[WARNING] thread Thread[org.apache.hadoop.fs.FileSystem$Statistics$StatisticsDataReferenceCleaner,5,spiritlab.sparkfhe.example.basic.DotProductExample] will linger despite being asked to die via interruption
[WARNING] thread Thread[shuffle-chunk-fetch-handler-4-1,5,spiritlab.sparkfhe.example.basic.DotProductExample] will linger despite being asked to die via interruption
[WARNING] thread Thread[broadcast-exchange-0,5,spiritlab.sparkfhe.example.basic.DotProductExample] will linger despite being asked to die via interruption
[WARNING] NOTE: 3 thread(s) did not finish despite being asked to via interruption. This is not a problem with exec:java, it is a problem with the running code. Although not serious, it should be remedied.
[WARNING] Couldn't destroy threadgroup org.codehaus.mojo.exec.ExecJavaMojo$IsolatedThreadGroup[name=spiritlab.sparkfhe.example.basic.DotProductExample,maxpri=10]
java.lang.IllegalThreadStateException
at java.lang.ThreadGroup.destroy(ThreadGroup.java:778)
at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:321)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)