Hi Roy,
Are you proposing to contribute this to OpenJDK or are you just looking
for feedback? If the former then the information needs to be hosted on
OpenJDK infrastructure so people can safely look at it.
Cheers,
David
On 1/10/2026 9:57 pm, Roy Zhang wrote:
Hi JFR Experts,
We built something on JFR that we'd like your eyes on — not a bug, a
usage pattern that quietly depends on some JFR-internal behaviors we'd
love expert confirmation of.
*The gap*: production JFR tells us what resources were consumed
(ExecutionSample, ObjectAllocation, SocketRead) and where (thread,
stack) — but never on behalf of which API. "What did this API cost
me?" is the question every service owner asks, and JFR couldn't answer
it. Now it can.
*How*: one custom event per request — an interval marker,
@StackTrace(false), begin in a servlet filter, commit in its finally.
Every other event is attributed to the API by threadId + startTime ∈
[begin, commit]. The fun part is cross-thread: worker threads rebuild
the marker from TTL-propagated context, so async samples land on the
right API too — 97–99% measured, virtual threads included.
*The ask*: Section 4 of the write-up has 6 questions born from
assumptions we couldn't verify from source alone — clock-domain
consistency across event writers, custom-vs-VM event ordering,
String-pool pressure, and whether a "marker event" idiom deserves
native JFR support. Your answers either validate the foundation or
catch a subtle breakage before production does.
Full write-up:
https://docs.google.com/document/d/1ml1y1__btqGdYiJwMtT6rXVcBrXeP3qlyc1gb6m9S3U/edit?usp=sharing
Any comment is appreciated :)
Thanks,
Roy
