Java 11 console app hangs if event in flight

[bruno-garcia]

Running a Java 11 console app, init and capture 1 event just hangs:

package io.benchmark;

import io.sentry.Sentry;

public class App 
{
    public static void main(String[] args) throws Exception
    {
        Sentry.init(o -> {
            o.setDsn("http://key@localhost:5000/1");
        });

        Sentry.captureMessage("hi");
    }
}

If I init but don't capture, it exists quickly. If I capture message, over 10 seconds hanging, then spits out some warnings and errors:

Output

``` ➜ java git:(main) ✗ mvn compile exec:java

[INFO] Scanning for projects...
[INFO]
[INFO] --------------------------< io.benchmark:App >--------------------------
[INFO] Building benchmark 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ App ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/bruno/git/sdk-transport-throughput/java/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ App ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- exec-maven-plugin:3.0.0:java (default-cli) @ App ---
[WARNING] thread Thread[SentryAsyncConnection-0,5,io.benchmark.App] was interrupted but is still alive after waiting at least 15000msecs
[WARNING] thread Thread[SentryAsyncConnection-0,5,io.benchmark.App] will linger despite being asked to die via interruption
[WARNING] NOTE: 1 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=io.benchmark.App,maxpri=10]
java.lang.IllegalThreadStateException: Has threads
at java.lang.ThreadGroup.destroyImpl (ThreadGroup.java:274)
at java.lang.ThreadGroup.destroy (ThreadGroup.java:256)
at org.codehaus.mojo.exec.ExecJavaMojo.execute (ExecJavaMojo.java:293)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:566)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 15.699 s
[INFO] Finished at: 2020-12-23T22:37:20-05:00
[INFO] ------------------------------------------------------------------------
➜ java git:(main) ✗

</details>

[maciejwalkowiak]

I am not able to reproduce it using Maven 3.6.3 with AdoptOpenJDK Java 11.0.9 HotSpot and AdoptOpenJDK Java 11.0.9 J9. Could you please specify exactly which Java version do you use? Are you able to reproduce it each time you run the code?

[bruno-garcia]

Yeah it was repro on each run. If I removed capture it would exit immediately.
Not sure what was wrong, I believe I was on JDK 11.

If you can't repro lets leave it, next time I get to this sample I'll try again and update this issue.

[maciejwalkowiak]

I think I've found an issue. It's due to the nature of Maven exec plugin. Add <cleanupDaemonThreads>false</cleanupDaemonThreads> to the configuration and problem should be gone. We use the same property in getsentry/examples project.

[bruno-garcia]

Thanks @maciejwalkowiak !