Hoist local vars for exception probes

[jpbempel]

What Does This Do

Exception probe instrumentation was not performing hoisting of local vars which is in fact required if we want to capture those locals because the wrapping with try/catch of the whole method body create sub scope preventing locals to be captured in the catch clause.

Motivation

Additional Notes

Contributor Checklist

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Jira ticket: DEBUG-5838

[dd-octo-sts]

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[datadog-datadog-prod-us1-2]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 57.17% (-0.01%)

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[datadog-datadog-prod-us1-2]

More details

The hoisting-before-computeFrames ordering in ExceptionInstrumenter is safe: the inserted STORE instructions use node-identity equality in the frames IdentityHashMap so frames for original RETURN nodes are unaffected. The ConfigurationUpdater change is a correct refactoring — injected config and Config.get() are the same singleton in production, and the test mock's stubbed values match the real defaults for every method DebuggerTransformer calls.

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[pr-commenter]

Debugger benchmarks

Parameters

	Baseline	Candidate
baseline_or_candidate	baseline	candidate
ci_job_date	1784139379	1784139726
end_time	2026-07-15T18:17:45	2026-07-15T18:23:31
git_branch	master	jpbempel/add-hoisting-for-er
git_commit_sha	d3d2e12	e8a8fe1
start_time	2026-07-15T18:16:20	2026-07-15T18:22:07

See matching parameters

	Baseline	Candidate
ci_job_id	1862793250	1862793250
ci_pipeline_id	124839006	124839006
cpu_model	Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz	Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz
git_commit_date	1784138737	1784138737

Summary

Found 0 performance improvements and 0 performance regressions! Performance is the same for 9 metrics, 6 unstable metrics.

See unchanged results

scenario	Δ mean agg_http_req_duration_min	Δ mean agg_http_req_duration_p50	Δ mean agg_http_req_duration_p75	Δ mean agg_http_req_duration_p99	Δ mean throughput
scenario:noprobe	unstable [-36.729µs; +25.676µs] or [-12.226%; +8.547%]	unstable [-53.084µs; +35.293µs] or [-15.399%; +10.238%]	unstable [-64.961µs; +45.168µs] or [-17.952%; +12.482%]	unstable [-128.919µs; +100.371µs] or [-11.026%; +8.584%]	same
scenario:basic	same	same	same	unstable [-103.509µs; +135.445µs] or [-9.716%; +12.714%]	unstable [-108.011op/s; +229.962op/s] or [-4.428%; +9.428%]
scenario:loop	same	same	same	same	same

Request duration reports for reports

gantt
    title reports - request duration [CI 0.99] : candidate=None, baseline=None
    dateFormat X
    axisFormat %s
section baseline
noprobe (344.717 µs) : 294, 395
.   : milestone, 345,
basic (298.792 µs) : 292, 306
.   : milestone, 299,
loop (8.979 ms) : 8957, 9001
.   : milestone, 8979,
section candidate
noprobe (335.821 µs) : 304, 368
.   : milestone, 336,
basic (296.899 µs) : 290, 304
.   : milestone, 297,
loop (8.968 ms) : 8963, 8973
.   : milestone, 8968,

Loading

• baseline results

Scenario	Request median duration [CI 0.99]
noprobe	344.717 µs [294.474 µs, 394.959 µs]
basic	298.792 µs [291.565 µs, 306.018 µs]
loop	8.979 ms [8.957 ms, 9.001 ms]

• candidate results

Scenario	Request median duration [CI 0.99]
noprobe	335.821 µs [304.115 µs, 367.528 µs]
basic	296.899 µs [290.099 µs, 303.698 µs]
loop	8.968 ms [8.963 ms, 8.973 ms]

[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.97 s	14.04 s	[-1.3%; +0.3%] (no difference)
startup:insecure-bank:tracing:Agent	12.90 s	12.96 s	[-1.2%; +0.3%] (no difference)
startup:petclinic:appsec:Agent	15.91 s	16.74 s	[-10.8%; +0.9%] (unstable)
startup:petclinic:iast:Agent	16.96 s	16.96 s	[-1.1%; +1.2%] (no difference)
startup:petclinic:profiling:Agent	16.58 s	16.77 s	[-2.4%; +0.3%] (no difference)
startup:petclinic:sca:Agent	16.85 s	16.72 s	[-0.2%; +1.6%] (no difference)
startup:petclinic:tracing:Agent	16.09 s	16.09 s	[-1.0%; +1.0%] (no difference)

Commit: e8a8fe1d · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

[datadog-datadog-prod-us1-2]

Bits has a CI fix ready

🟢 Investigated · 🟢 Fix prepared · ⚪ Validation skipped · 🟠 Ready

ExceptionProbeInstrumentationTest.instrumentAndCaptureSnapshots now skips on J9, whose class retransformation omits the local-variable metadata required by the new capture assertions.

Commit fix to this PR

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View in Datadog | Reviewed commit 154692d