[PROF-15616] Add JFR support and java_cpu_jfr scenario by r1viollet · Pull Request #156 · DataDog/prof-correctness

r1viollet · 2026-07-02T15:37:49Z

What

Add Java Flight Recorder (JFR) support to the analyzer as a first-class input format via the neutral ProfileSet model.

The analyzer now follows the same shape for all supported profile formats:

pprof -> FromPprof -> ProfileSet
OTLP -> FromOTLP -> ProfileSet
JFR -> FromJFR -> ProfileSet

The JFR path no longer converts recordings to synthetic pprof files. It reads raw JFR events and maps supported event types directly to semantic profile samples.

Currently supported JFR CPU events:

jdk.ExecutionSample
datadog.ExecutionSample

How

Add analysis/jfr.go with direct JFR-to-ProfileSet parsing.
Dispatch .jfr files through LoadProfileSet alongside pprof and OTLP.
Stop pre-converting .jfr files to generated *_cpu.pprof files in AnalyzeResults.
Use a jfr-parser fork exposing raw JFR events and decoded raw fields so prof-correctness owns producer-specific semantic mapping without carrying JFR wire-decoding code.
Keep unsupported JFR event types ignored for now instead of forcing them through a pprof conversion layer.
Preserve JFR CPU duration from chunk headers for duration-scaled assertions.
Preserve Datadog localRootSpanId as the neutral local root span id label.

Scenario

Add scenarios/java_cpu_jfr, which runs the Datadog Java profiler through dd-java-agent and captures a local JFR through the tracer's built-in debug dump path.

The scenario:

installs dd-java-agent.jar
enables Datadog profiling / ddprof
runs a recursive Fibonacci workload
sets dd.profiling.debug.dump_path=/app/data/dumps
matches the generated dd-profiler-debug-*.jfr file by regex
asserts CPU samples contain DummyApp.fibonacci

This intentionally validates Datadog profiler JFR output, not HotSpot's built-in -XX:StartFlightRecording output.

The profile-upload/intake path is not modeled in this PR. A fake Datadog profile intake would be useful as shared test-harness infrastructure, but should be implemented generically in Go and reused across languages rather than embedded in this Java JFR scenario.

Testing

GOPRIVATE=github.com/r1viollet/pyroscope-jfr-parser \
GONOSUMDB=github.com/r1viollet/pyroscope-jfr-parser \
GOPROXY=direct \
go test ./analysis ./cmd/prof-analyze

GOPRIVATE=github.com/r1viollet/pyroscope-jfr-parser \
GONOSUMDB=github.com/r1viollet/pyroscope-jfr-parser \
GOPROXY=direct \
TEST_SCENARIOS=java_cpu_jfr TEST_RUN_SECS=40 \
go test -run TestScenarios -count=1

Both pass locally.

Notes

This currently depends on a temporary parser fork:

replace github.com/grafana/jfr-parser => github.com/r1viollet/pyroscope-jfr-parser v0.0.0-20260803080954-eddc025c5c4e

Parser fork PR for review/upstreaming:

Expose raw JFR events and decoded fields r1viollet/pyroscope-jfr-parser#1

Before merging, this should move to a Datadog fork or an upstream jfr-parser change exposing raw events/fields.

r1viollet · 2026-07-09T11:43:07Z

@jbachorik do you prefer converting in the framework ? Or in the test scenario ?
This is in the framework

jbachorik · 2026-07-09T11:55:24Z

@r1viollet If we are ok with maintaining the go parser of JFR and are sure it won't hamper the correctness check, in-framework is a better fit.
Who would be on the hook to fix the go jfr parser if we encounter any issues? Perhaps it is less of a concerns with agentic coding tools but still we should have someone making sure we don't make correctness tests incorrect or failing...

r1viollet · 2026-07-09T12:00:31Z

... someone making sure we don't make correctness tests incorrect or failing...

I agree that there is a question of ownership. I'm fine helping with the design of prof-correctness, but I won't be checking results. It has been quite low overhead to maintain the framework while we don't make big evolutions to the format.
I would expect java folks to still enrich the tests and investigate failures.

r1viollet · 2026-07-17T12:01:46Z

Let's push for this, if things break, we'll just remove them

Add the ability to parse Java Flight Recorder (.jfr) files as part of the correctness analysis pipeline. analysis/jfr.go: - parseJFR(): converts raw JFR bytes to a map of metric name → *profile.Profile, using github.com/grafana/jfr-parser/parser directly (no pyroscope/api dependency). - convertJFRFiles(): called at the start of AnalyzeResults; walks the output directory for *.jfr files and writes per-metric pprof files (e.g. profile.jfr → profile_cpu.pprof, profile_lock.pprof, …). Existing pprof analysis code then picks these up via the normal filename-regex matching. Supported JFR event types: jdk.ExecutionSample (cpu/wall), jdk.ObjectAllocationInNewTLAB, jdk.ObjectAllocationOutsideTLAB, jdk.JavaMonitorEnter, and the Datadog WallClockSample extension. scenarios/java_cpu_jfr: - Simple Fibonacci CPU burner recorded with built-in JDK JFR (eclipse-temurin:21-jdk, settings=profile, dumponexit=true). - Asserts ≥80% of CPU samples contain DummyApp.fibonacci. - EXECUTION_TIME_SEC env var honoured (default 30 s).

r1viollet · 2026-08-03T08:03:54Z

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r1viollet · 2026-08-03T08:34:43Z

 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/r1viollet/pyroscope-jfr-parser v0.0.0-20260803080954-eddc025c5c4e h1:qOsPPgSArMHlR10zugkK6l5pCZp+8fK99pIcwxpYJ7M=


for now, upstream jfr parser handles a subset of events

r1viollet · 2026-08-03T12:47:17Z

@jbachorik this is starting to make sense

r1viollet · 2026-08-03T12:48:19Z

+		}
+
+		switch event.Type.Name {
+		case "jdk.ExecutionSample", "datadog.ExecutionSample":


I did not handle everything here, this is mainly to have an example

r1viollet marked this pull request as ready for review July 17, 2026 12:01

r1viollet requested a review from a team as a code owner July 17, 2026 12:01

jbachorik reviewed Jul 17, 2026

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r1viollet changed the base branch from main to r1viollet/analysis-otlp-native July 28, 2026 11:00

r1viollet marked this pull request as draft July 28, 2026 14:30

Base automatically changed from r1viollet/analysis-otlp-native to main August 3, 2026 07:26

r1viollet added 4 commits August 3, 2026 09:33

ci: add java job for JFR scenarios

9bd5b68

Generalize JFR pprof conversion

1e07eb3

Use JFR parser fork with Datadog event aliases

8a8ba18

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r1viollet added 2 commits August 3, 2026 10:15

Parse JFR directly into profile model

d8e9594

Run Java JFR scenario with Datadog profiler

96c4983

r1viollet force-pushed the r1viollet/jfr-support branch from cf77dde to 96c4983 Compare August 3, 2026 08:16

r1viollet commented Aug 3, 2026

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r1viollet changed the title ~~[PROF-XXXX] Add JFR support and java_cpu_jfr scenario~~ [PROF-15616] Add JFR support and java_cpu_jfr scenario Aug 3, 2026

r1viollet marked this pull request as ready for review August 3, 2026 08:49

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[PROF-15616] Add JFR support and java_cpu_jfr scenario - #156

[PROF-15616] Add JFR support and java_cpu_jfr scenario#156
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