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https://issues.apache.org/jira/browse/LIVY-1001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17856376#comment-17856376
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wangdengshan commented on LIVY-1001:
------------------------------------
[https://github.com/apache/incubator-livy/pull/447]
> ContextLauncher has a potential NullPointerException exception during the
> livy session creating process.
> --------------------------------------------------------------------------------------------------------
>
> Key: LIVY-1001
> URL: https://issues.apache.org/jira/browse/LIVY-1001
> Project: Livy
> Issue Type: Bug
> Components: RSC
> Affects Versions: 0.8.0
> Reporter: wangdengshan
> Priority: Major
> Labels: patch
> Original Estimate: 168h
> Remaining Estimate: 168h
>
> Below is the exception stack I printed out
> {color:#ff8b00}2024-05-30 03:39:12 [ERROR]
> [LivyServer2-Background-Create-Session-Pool: Thread-139976]
> org.apache.livy.thriftserver.LivyThriftSessionManager:error:58 - Create
> session failed!{color}
> {color:#ff8b00}java.lang.NullPointerException{color}
> {color:#ff8b00} at
> org.apache.livy.rsc.ContextLauncher.<init>(ContextLauncher.java:86){color}
> {color:#ff8b00} at
> org.apache.livy.rsc.ContextLauncher.create(ContextLauncher.java:73){color}
> {color:#ff8b00} at
> org.apache.livy.rsc.RSCClientFactory.createClient(RSCClientFactory.java:72){color}
> {color:#ff8b00} at
> org.apache.livy.LivyClientBuilder.build(LivyClientBuilder.java:174){color}
> {color:#ff8b00} at
> org.apache.livy.server.interactive.InteractiveSession$.$anonfun$create$1(InteractiveSession.scala:195){color}
> {color:#ff8b00} at scala.Option.orElse(Option.scala:447){color}
> {color:#ff8b00} at
> org.apache.livy.server.interactive.InteractiveSession$.create(InteractiveSession.scala:99){color}
> {color:#ff8b00} at
> org.apache.livy.thriftserver.LivyThriftSessionManager.$anonfun$openSession$3(LivyThriftSessionManager.scala:437){color}
> {color:#ff8b00} at
> org.apache.livy.thriftserver.LivyThriftSessionManager.org$apache$livy$thriftserver$LivyThriftSessionManager$$getOrCreateLivySession(LivyThriftSessionManager.scala:340){color}
> {color:#ff8b00} at
> org.apache.livy.thriftserver.LivyThriftSessionManager$$anon$1.run(LivyThriftSessionManager.scala:454){color}
> {color:#ff8b00} at
> org.apache.livy.thriftserver.LivyThriftSessionManager$$anon$1.run(LivyThriftSessionManager.scala:450){color}
> {color:#ff8b00} at java.security.AccessController.doPrivileged(Native
> Method){color}
> {color:#ff8b00} at
> javax.security.auth.Subject.doAs(Subject.java:422){color}
> {color:#ff8b00} at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:2248){color}
> {color:#ff8b00} at
> org.apache.livy.thriftserver.LivyThriftSessionManager.$anonfun$openSession$4(LivyThriftSessionManager.scala:450){color}
> {color:#ff8b00} at
> scala.concurrent.Future$.$anonfun$apply$1(Future.scala:659){color}
> {color:#ff8b00} at
> scala.util.Success.$anonfun$map$1(Try.scala:255){color}
> {color:#ff8b00} at scala.util.Success.map(Try.scala:213){color}
> {color:#ff8b00} at
> scala.concurrent.Future.$anonfun$map$1(Future.scala:292){color}
> {color:#ff8b00} at
> scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:33){color}
> {color:#ff8b00} at
> scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33){color}
> {color:#ff8b00} at
> scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64){color}
> {color:#ff8b00} at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149){color}
> {color:#ff8b00} at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624){color}
> {color:#ff8b00} at java.lang.Thread.run(Thread.java:748){color}
>
> {color:#172b4d}By troubleshooting the code, we found that the problem may
> occur in the creation of RpcServer and the processing of refCount reference
> logic.{color}
> {code:java}
> private synchronized void ref(RSCConf config) throws IOException {
> if (refCount.get() != 0) {
> refCount.incrementAndGet();
> return;
> }
> Utils.checkState(server == null, "Server already running but ref count is
> 0.");
> if (server == null) {
> try {
> server = new RpcServer(config);
> } catch (InterruptedException ie) {
> throw Utils.propagate(ie);
> }
> }
> refCount.incrementAndGet();
> }
> synchronized void unref() {
> if (refCount.decrementAndGet() == 0) {
> server.close();
> server = null;
> }
> } {code}
> {color:#172b4d}This problem will occur if an exception is thrown during the
> new RpcServer process{color}
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