Proposal to introduce method "Instrumentation.getInstance()" to instrument the current VM

[Remi Forax]

On September 29, 2016 9:06:12 PM GMT+02:00, Alan Bateman <Alan.Bateman at oracle.com> wrote:
>On 29/09/2016 18:50, Rafael Winterhalter wrote:
>
>> :
>>
>> Therefore I want to propose adding a static method to the
>Instrumentation
>> interface:
>>
>> interface Instrumentation {
>>    static Instrumentation getInstance(boolean redefine, boolean
>retransform,
>> boolean nativePrefix) {
>>      // security manager check
>>      return getInstance0(redefine, retransform, nativePrefix);
>>    }
>> }
>>

I've a code that also does that for implementing a Repl like JShell.

>The original intention, back in JSR 163, was that java.lang.instrument 
>be for instrumentation agents, not applications. This is why the API 
>deliberately does not include a method to get the Instrumentation
>object 
>along the lines you have propose. Sure, you can leak it from an agent 
>started on the command line or attached at runtime but that is not the 
>original intention. So I think introducing this method is a very 
>significant change that would require a lot of consideration (previous 
>requests to provide a way for applications to get the Instrumentation 
>object without an agent in the picture were resisted).
>
>Separately, introducing this method creates a complication for runtimes
>
>that do not have JVM TI support (the JPLIS agent is based on JVM TI).
>As 
>things stand then it's possible to create a runtime that does not have
>a 
>means to start agents from the command-line (the spec allows this) and 
>so there is no need to have the implementation support for this API. So
>
>if a method like this is every introduced then it would either have to 
>be optional or it would require changes to the JVM TI spec to make it 
>non-optional (or is based on an alternative JPLIS implementation that 
>doesn't use JVM TI).

Having it optional seams fine.
Perhaps it has to be activated by a command line argument too.

>
>-Alan

Rémi 

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