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Posted to commits@pulsar.apache.org by GitBox <gi...@apache.org> on 2022/09/06 00:58:15 UTC

[GitHub] [pulsar] labuladong opened a new issue, #17480: [Bug][Java client] main thread won't exit if not close pulsar client

labuladong opened a new issue, #17480:
URL: https://github.com/apache/pulsar/issues/17480

   ### Search before asking
   
   - [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.
   
   
   ### Version
   
   macOS 12.5.1 
   
   Pulsar 2.10.1
   
   Pulsar Java client 2.10.1
   
   ### Minimal reproduce step
   
   Run this snippet:
   
   ```java
   public class Main {
       public static void main(String[] args) throws PulsarClientException {
           PulsarClient client = PulsarClient.builder()
                   .serviceUrl("pulsar://localhost:6650")
                   .build();
   
           System.out.println("hello world"); // print successfully
           // without client.close(), `main` will be hanging, never exit
       }
   }
   ```
   
   
   ### What did you expect to see?
   
   Print `hello world` then exit normally.
   
   ### What did you see instead?
   
   Print `hello world` but never exit.
   
   ### Anything else?
   
   I know I should always `close` the client manually. But if I don't close it, is hanging to be the expected behavior?
   
   ### Are you willing to submit a PR?
   
   - [X] I'm willing to submit a PR!


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[GitHub] [pulsar] nicoloboschi commented on issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
nicoloboschi commented on issue #17480:
URL: https://github.com/apache/pulsar/issues/17480#issuecomment-1237964085

   @labuladong if you close the Pulsar client (`client.close()`) the process exits? 


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[GitHub] [pulsar] labuladong closed issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
labuladong closed issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client
URL: https://github.com/apache/pulsar/issues/17480


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[GitHub] [pulsar] labuladong commented on issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
labuladong commented on issue #17480:
URL: https://github.com/apache/pulsar/issues/17480#issuecomment-1238819175

   > @labuladong if you close the Pulsar client (`client.close()`) the process exits?
   
   Yes, it will.


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[GitHub] [pulsar] lhotari commented on issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
lhotari commented on issue #17480:
URL: https://github.com/apache/pulsar/issues/17480#issuecomment-1237979028

   > We (+ @yaalsn) discuss this, seems that netty has a shutdown hook to prevent client exit.
   
   Live non-daemon threads are a common reason why normal shutdown doesn't happen in a Java application.
   
   The [javadoc of java.lang.Thread](https://docs.oracle.com/javase/8/docs/api/java/lang/Thread.html):
   
   >  When a Java Virtual Machine starts up, there is usually a single non-daemon thread (which typically calls the method named main of some designated class). The Java Virtual Machine continues to execute threads until either of the following occurs:
   > 
   > * The exit method of class Runtime has been called and the security manager has permitted the exit operation to take place.
   > * All threads that are not daemon threads have died, either by returning from the call to the run method or by throwing an exception that propagates beyond the run method.
   
   I believe that Pulsar client creates threads that are non-daemon threads. This might be intentional. 
   I assume that it's better to handle the shutdown in a controlled way in any case. 
   A simple fix to your problem is to add a shutdown hook that calls `client.close()`. 
   
   @labuladong What is your actual use case? Could you share more of the scenario that you have in mind?
   


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[GitHub] [pulsar] labuladong commented on issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
labuladong commented on issue #17480:
URL: https://github.com/apache/pulsar/issues/17480#issuecomment-1237556067

   We (+ @yaalsn) discuss this, seems that netty has a shutdown hook to prevent client exit.


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[GitHub] [pulsar] labuladong commented on issue #17480: [Bug][Java client] main thread won't exit if not close pulsar client

Posted by GitBox <gi...@apache.org>.
labuladong commented on issue #17480:
URL: https://github.com/apache/pulsar/issues/17480#issuecomment-1238819273

   @lhotari Hi, I'm just curious about how to exit even if missing `client.close()`. Now I figured it out from your answer. Thanks a lot!


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