On 19/06/2018 03:06, Erik Gahlin wrote:
Hi,
Could I have a review of an enhancement that will make it possible to
add JFR events to java.base, and possibly other modules in the JDK,
without a compile time dependency on jdk.jfr.
Bug:
https://bugs.openjdk.java.net/browse/JDK-8203629
Webrev:
http://cr.openjdk.java.net/~egahlin/8203629.0
Testing:
Tests in test/jdk/jdk/jfr
The functionality is a prerequisite for an upcoming enhancement that
will add JFR events to the security libraries.
In short, jdk.jfr.Event (located in jdk.jfr) extends
jdk.internal.event.Event (located in java.base). Metadata for events,
such as labels and descriptions, are added using a mirror event class
located in jdk.jfr module. If the fields of the mirror class and the
event class don't match an InternalError is thrown.
To illustrate how the mechanism can be used, see the following example
(not meant to be checked in).
http://cr.openjdk.java.net/~egahlin/8203629.example
Since the implementation of jdk.internal.event.Event is empty, the JIT
will typically eliminate all traces of JFR functionality unless Flight
Recorder is enabled.
Adding a way to get events from java.base is good but I wonder if
jdk.internal.event.Event could be cleaned up before you push this. It
would be nice to have a class description and some minimal method
descriptions too. Also all the methods are empty which makes me wonder
if they should be abstract (as the class is abstract) or whether it
should be an interface. Some of the method modifiers are in unusual
order and it would be good to get those cleaned up too.
-Alan
