RFR: 8357828: Add a timestamp to jcmd diagnostic commands

[Ivan Bereziuk]

On Wed, 24 Sep 2025 22:24:35 GMT, Larry Cable <duke at openjdk.org> wrote:

>      My proposal would entail
>      * adding a new standard option to jcmd
>      * somehow funneling that option to the JVM
>      * the option should be optional, so that:
>      * old jcmd still works with new JVMs (and produces legacy jcmd output)
>      * new jcmd still works with old JVMs (and produces legacy jcmd output)
>      How complex would this be? There are two approaches to this. You
>      can either create a new attach listener protocol (we already have
>      ATTACH_API_V2 vs ATTACH_API_V1, so the precedence is there). Or,
>      you can expand the jcmd parsing (see |jcmd(AttachOperation* op,
>      attachStream* out)| in attachListener.cpp).
> 
>  ATTACH_API_V2 supports "options".
>  Client (jcmd) detects options supported by the target VM ("getversion
>  options" command) and can set option values in attach command request.
>  Currently the only supported option is "streaming" (it allows turn off
>  streaming output).
>  The option is needed only for tests and needs to work for all attach
>  tools (jcmd, jstack, etc.), so it can be set by specifying java
>  property launching attach tool (like |jcmd
>  -J-Djdk.attach.allowStreamingOutput=false PID command|)

Agreed. I will be working on the proposal. Thank you.

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PR Comment: https://git.openjdk.org/jdk/pull/27368#issuecomment-3360367314