Proposal for back-porting JFR to OpenJDK8u

[Mario Torre]

On Thu, Dec 6, 2018 at 10:38 AM Andrew Haley <aph at redhat.com> wrote:
>
> Hi,
>
> On 12/5/18 12:56 PM, Mario Torre wrote:
> > On Wed, Dec 5, 2018 at 10:56 AM guangyu.zhu <guangyu.zhu at aliyun.com> wrote:
> >>
> >> Java Flight Recorder (JFR) has been open-sourced in OpenJDK 11 for some time. The tool is very useful for trouble-shooting and performance tuning. However, a lot of Java applications are still running on JDK 8. Thus we back-ported JFR from 11 to 8 on x86-64 platform, which actually has been widely used at Alibaba. We believe it is stable enough to be contributed back to the community.  By contributing our patch, the community can help make it work on other platforms too. So, I’d like to file a JEP and propose contributing it to OpenJDK8project, then people can work together to make the patch be pushed finally. What do you think?
> >>
> >> Thanks,
> >> Guangyu (Greg) Zhu
> >
> > This is awesome, I've been toying with this idea myself lately, so I'm
> > very happy you would like to contribute this code, I would support
> > this proposal completely, and I'm very curious to see the actual
> > patch.
> >
> > I think you are right in filing a JEP, it's the right approach for such changes.
>
> I'm not convinced that JEPs are appropriate for backports to jdk8u. We
> should instead evaluate this as a feature backport.

Makes sense.

> We cannot change any APIs in the core Java namespaces. This is a legal
> requirement.

The Flight Recorder API adds classes under the "jdk.jfr" namespace and
in "jdk/management/jfr" (for the remote MXBean control), anything else
is internal as far as I understand, and afaik those aren't official
namespaces in JDK 8. I think we need to see the patch to properly
evaluate, however do you think adding the namespaces I just mentioned
would be a problem?

We can certainly change those names however, although that will mean
some incompatibility across OpenJDK versions.

Cheers,
Mario

-- 
Mario Torre
Associate Manager, Software Engineering
Red Hat GmbH <https://www.redhat.com>
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