Make snapshot list for ThrowableState concurrent

[jpbempel]

What Does This Do

use CopyOnWriteArrayList instead of plain ArrayList We have capping to max 256 items

Motivation

Additional Notes

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

Jira ticket: DEBUG-6047

[datadog-datadog-prod-us1-2]

More details

The concurrent list keeps the existing append order. It supports concurrent snapshot reads and writes without a collection behavior change.

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[datadog-datadog-prod-us1-2]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 74.40% (+15.60%)

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[pr-commenter]

Debugger benchmarks

Parameters

	Baseline	Candidate
baseline_or_candidate	baseline	candidate
ci_job_date	1787575573	1787575899
end_time	2026-08-24T12:47:40	2026-08-24T12:53:06
git_branch	master	jpbempel/fix-concurrency-in-er-snapshot-list
git_commit_sha	2010236	493d8eb
start_time	2026-08-24T12:46:14	2026-08-24T12:51:40

See matching parameters

	Baseline	Candidate
ci_job_id	1976483246	1976483246
ci_pipeline_id	132737408	132737408
cpu_model	Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz	Intel(R) Xeon(R) Platinum 8259CL CPU @ 2.50GHz
git_commit_date	1787575003	1787575003

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 [-22.086µs; +19.483µs] or [-7.109%; +6.271%]	unstable [-29.336µs; +35.888µs] or [-8.521%; +10.425%]	unstable [-38.348µs; +45.191µs] or [-10.700%; +12.609%]	unstable [-74.897µs; +120.412µs] or [-6.493%; +10.439%]	same
scenario:basic	same	same	same	unstable [-185.087µs; +43.375µs] or [-17.588%; +4.122%]	unstable [-126.669op/s; +126.669op/s] or [-5.447%; +5.447%]
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 (344.262 µs) : 313, 376
.   : milestone, 344,
basic (324.27 µs) : 318, 330
.   : milestone, 324,
loop (8.095 ms) : 8032, 8158
.   : milestone, 8095,
section candidate
noprobe (347.538 µs) : 317, 378
.   : milestone, 348,
basic (325.561 µs) : 319, 332
.   : milestone, 326,
loop (8.097 ms) : 8034, 8160
.   : milestone, 8097,

Loading

• baseline results

Scenario	Request median duration [CI 0.99]
noprobe	344.262 µs [312.935 µs, 375.588 µs]
basic	324.27 µs [318.274 µs, 330.265 µs]
loop	8.095 ms [8.032 ms, 8.158 ms]

• candidate results

Scenario	Request median duration [CI 0.99]
noprobe	347.538 µs [316.881 µs, 378.194 µs]
basic	325.561 µs [319.169 µs, 331.953 µs]
loop	8.097 ms [8.034 ms, 8.16 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	13.99 s	14.04 s	[-1.1%; +0.4%] (no difference)
startup:insecure-bank:tracing:Agent	12.93 s	13.01 s	[-1.1%; -0.0%] (maybe better)
startup:petclinic:appsec:Agent	16.87 s	16.76 s	[-0.1%; +1.4%] (no difference)
startup:petclinic:iast:Agent	16.82 s	16.97 s	[-1.8%; +0.0%] (no difference)
startup:petclinic:profiling:Agent	16.58 s	16.78 s	[-2.2%; -0.2%] (maybe better)
startup:petclinic:sca:Agent	16.71 s	16.53 s	[+0.2%; +2.1%] (maybe worse)
startup:petclinic:tracing:Agent	16.02 s	16.24 s	[-2.2%; -0.5%] (maybe better)

Commit: 493d8eb8 · CI Pipeline · Benchmarking Platform UI

---

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

[jpbempel]

/merge

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2026-08-28 12:09:45 UTC ℹ️ Start processing command /merge

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2026-08-28 12:09:55 UTC ℹ️ MergeQueue: Pull request is not mergeable yet

It will be processed automatically as soon as GitHub reports it as mergeable. View in MergeQueue UI.

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2026-08-28 12:11:23 UTC ℹ️ MergeQueue: merge request added to the queue

The expected merge time in master is approximately 2h (p90).

---

2026-08-28 13:12:23 UTC ℹ️ MergeQueue: This merge request was merged

[dd-octo-sts]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-08-28 12:10:43 UTC ℹ️ Start processing command /merge

---

2026-08-28 12:10:45 UTC ❌ MergeQueue

PR already in the queue with status waiting