Extend jcmd to java application level

[Yasumasa Suenaga]

Hi Denghui,

I thought to add JMX client feature to jcmd in the past for similar purposes, but I didn't because JMX URL is too complex to type into console :)

Your proposal is useful, but it means malicious users can inject arbitrary code. I think we need to consider security, and existing framework like JMX might help us.


Thanks,

Yasumasa


On 2021/10/08 10:09, Denghui Dong wrote:
> Hi Yasumasa,
> 
> JVMTI.data_dump and DataDumpRequest can achieve the purpose of triggering.
> 
> IIUC, DataDumpRequest does not seem to be able to pass parameters.
> And sometimes the action the user wants to trigger may not be a data dump.
> 
> In fact, I think that commands such as JFR.start/stop are such a mechanism, triggered by `jcmd`, and finally callback to the java layer.
> 
> Denghui Dong
> 
>     ------------------------------------------------------------------
>     From:Yasumasa Suenaga <suenaga at oss.nttdata.com>
>     Send Time:2021年10月8日(星期五) 07:45
>     To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; serviceability-dev <serviceability-dev at openjdk.java.net>; hotspot-runtime-dev at openjdk.java.net <hotspot-runtime-dev at openjdk.java.net>
>     Subject:Re: Extend jcmd to java application level
> 
>     Hi Denghui,
> 
> 
>     I think you can do it with combination of JVMTI.data_dump dcmd and DataDumpRequest event in JVMTI.
> 
>     JVM(TM) Tool Interface 17.0.0 (oracle.com) <https://docs.oracle.com/en/java/javase/17/docs/specs/jvmti.html#DataDumpRequest>
> 
> 
>     Thanks,
> 
>     Yasumasa
> 
> 
>     On 2021/10/07 22:58, Denghui Dong wrote:
> 
>     Hi team,
> 
>     The `jcmd` command can be used to call some built-in diagnostic commands in vm.
>     Can we consider extending it to the java layer like perf data, so that Java developers can
>     customize their diagnostic commands and then call them through `jcmd`?
> 
>     One application scenario I can think of for this extension is that some statistical information
>     may be collected in a java application. Triggering the output of this statistical information through
>     the `jcmd` command seems to me relative to other mechanisms that trigger output (such as through
>     an HTTP service, or periodic Printing) is more convenient.
> 
>     Any input is appreciated.
> 
>     Thanks,
>     Denghui Dong
> 
>