[jira] [Commented] (CASSANDRA-7254) NPE on startup if another Cassandra instance is already running

["Shannon Carey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7254?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15658039#comment-15658039 ] 

Shannon Carey commented on CASSANDRA-7254:
------------------------------------------

This check causes Cassandra to freeze (block forever) if I use a JVM agent that tries to connect to the local JMX with `ManagementFactory.getPlatformMBeanServer()` (at least, I'm pretty sure that's why... it's definitely something to do with the agent.) It appears to only happen if we're using `com.sun.management.jmxremote.port` and not if we're only using `cassandra.jmx.local.port`. 

Can anyone explain why this happens? Is Cassandra doing something that causes other stuff to not be able to connect to the JMX port? Or is my agent's code not connecting properly?

> NPE on startup if another Cassandra instance is already running
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-7254
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7254
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Tyler Hobbs
>            Assignee: Brandon Williams
>            Priority: Minor
>             Fix For: 2.0.10, 2.1 rc3
>
>         Attachments: 7254.txt
>
>
> After CASSANDRA-7087, if you try to start cassandra while another instance is already running, you'll see something like this:
> {noformat}
> $ bin/cassandra -f
> Error: Exception thrown by the agent : java.lang.NullPointerException
> {noformat}
> This is probably a JVM bug, but we should confirm that, open a JVM ticket, and see if we can give a more useful error message on the C* side.



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