chore(antithesis): dogstatsd generation with byte limit by blt · Pull Request #1974 · DataDog/saluki

blt · 2026-07-02T00:56:13Z

Summary

This commit updates the harness driver to build dogstatsd to a byte
limit, in the manner of datadog/lading. I have been unable to
investigate SMPTNG-7611 well owing to the error log emission by Datadog
Agent. I've added property tests to assert the payload limit is obeyed,
accepting that this means making the dogstatsd generator pure with
regard to Rng and may not use antithesis SDK's random_* directly.

I have tweaked also how 'feral' load is produced, making payloads more
compact but also avoiding producing feral load that Datadog Agent will
not outright reject.

Change Type

Bug fix
New feature
Non-functional (chore, refactoring, docs)
Performance

How did you test this PR?

References

Discovered the following debugging this work:

DataDog/datadog-agent#53170
SMPTNG-761

blt · 2026-07-02T00:56:58Z

pr-commenter · 2026-07-02T01:04:11Z

Binary Size Analysis (Agent Data Plane)

Baseline: dff1654 · Comparison: 9fe3971 · diff
Analysis Configuration: stripped binaries · Pass/Fail Threshold: +5%
Sizes: 41.59 MiB (baseline) vs 41.59 MiB (comparison)
Size Change: +0 B (+0.00%)

✅ Binary size difference within threshold

Changes by Module

Module	File Size	Symbols
`anon.104b1f618a14d6d60f2ebe1b651d81f5.1.llvm.16633083741012894223`	+130 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.1.llvm.10234976937094269617`	-130 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.4.llvm.16633083741012894223`	+115 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.4.llvm.10234976937094269617`	-115 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.3.llvm.16633083741012894223`	+109 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.3.llvm.10234976937094269617`	-109 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.0.llvm.16633083741012894223`	+97 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.0.llvm.10234976937094269617`	-97 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.2.llvm.16633083741012894223`	+95 B	1
`anon.104b1f618a14d6d60f2ebe1b651d81f5.2.llvm.10234976937094269617`	-95 B	1

Detailed Symbol Changes

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [NEW]    +130  [NEW]     +40    anon.104b1f618a14d6d60f2ebe1b651d81f5.1.llvm.16633083741012894223
  [NEW]    +115  [NEW]     +25    anon.104b1f618a14d6d60f2ebe1b651d81f5.4.llvm.16633083741012894223
  [NEW]    +109  [NEW]     +19    anon.104b1f618a14d6d60f2ebe1b651d81f5.3.llvm.16633083741012894223
  [NEW]     +97  [NEW]      +7    anon.104b1f618a14d6d60f2ebe1b651d81f5.0.llvm.16633083741012894223
  [NEW]     +95  [NEW]      +5    anon.104b1f618a14d6d60f2ebe1b651d81f5.2.llvm.16633083741012894223
  [DEL]     -95  [DEL]      -5    anon.104b1f618a14d6d60f2ebe1b651d81f5.2.llvm.10234976937094269617
  [DEL]     -97  [DEL]      -7    anon.104b1f618a14d6d60f2ebe1b651d81f5.0.llvm.10234976937094269617
  [DEL]    -109  [DEL]     -19    anon.104b1f618a14d6d60f2ebe1b651d81f5.3.llvm.10234976937094269617
  [DEL]    -115  [DEL]     -25    anon.104b1f618a14d6d60f2ebe1b651d81f5.4.llvm.10234976937094269617
  [DEL]    -130  [DEL]     -40    anon.104b1f618a14d6d60f2ebe1b651d81f5.1.llvm.10234976937094269617
  [ = ]       0  [ = ]       0    TOTAL

pr-commenter · 2026-07-02T01:18:05Z

Regression Detector (Agent Data Plane)

Run ID: ebc88cc8-6790-4229-b5a5-577412d6081c
Baseline: dff16546 · Comparison: 9fe3971b · diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment (5)

Experiments configured erratic: true are tagged (ignored) and skipped when determining which experiments regressed or improved. Experiments which are detected as erratic at runtime are tagged (erratic) to flag that the run's sample dispersion was high, but their regression / improvement signal still counts.

experiment	goal	Δ mean %	links
quality_gates_rss_dsd_medium	memory	⚪ +0.18	metrics profiles logs
quality_gates_rss_dsd_heavy	memory	⚪ -0.03	metrics profiles logs
quality_gates_rss_idle	memory	⚪ -0.09	metrics profiles logs
quality_gates_rss_dsd_ultraheavy	memory	⚪ -0.10	metrics profiles logs
quality_gates_rss_dsd_low	memory	⚪ -0.14	metrics profiles logs

Bounds Checks: ✅ Passed (5)

experiment	check	replicates	observed	links
quality_gates_rss_dsd_heavy	memory_usage	10/10	✅ 132 MiB ≤ 140 MiB	metrics profiles logs
quality_gates_rss_dsd_low	memory_usage	10/10	✅ 43.2 MiB ≤ 50 MiB	metrics profiles logs
quality_gates_rss_dsd_medium	memory_usage	10/10	✅ 65.1 MiB ≤ 75 MiB	metrics profiles logs
quality_gates_rss_dsd_ultraheavy	memory_usage	10/10	✅ 192 MiB ≤ 200 MiB	metrics profiles logs
quality_gates_rss_idle	memory_usage	10/10	✅ 29 MiB ≤ 40 MiB	metrics profiles logs

Explanation

A change is flagged as a regression when |Δ mean %| > 5.00% in the regressing direction for its optimization goal AND SMP marks the experiment as a regression (is_regression: true). Improvements use the matching criteria for the improving direction. Experiments configured erratic: true (tagged (ignored)) are skipped outright; experiments detected as erratic at runtime (tagged (erratic)) still count, since that flag describes sample dispersion rather than directional certainty. The Δ mean % cell is colored accordingly: 🟢 = improvement, 🔴 = regression, ⚪ = neutral. Reduction in CPU or memory is an improvement; reduction in ingress throughput is a regression.

Copilot

Pull request overview

This PR updates the Antithesis DogStatsD harness to generate byte-limited, newline-packed payloads (instead of single lines) and refactors payload sampling to use rand’s slice/array selection APIs with an explicit RNG, adding property tests to lock in the new size/invariant behavior.

Changes:

Introduce PAYLOAD_BYTE_LIMIT, Payload, write_line, and write_payload to generate \n-terminated lines packed into datagrams without exceeding a byte limit.
Update the load driver to send payload datagrams and report sent line counts / max packed counts across payloads.
Add proptest-based invariants (and a regression seed file) for payload/line size and newline-count properties.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
test/antithesis/scenarios/general/src/bin/parallel_driver_send_dogstatsd.rs	Switch scenario to use `driver::sample()` after driver API refactor.
test/antithesis/scenarios/differential/src/bin/parallel_driver_send_dogstatsd_differential.rs	Update imports and batch sampling call site for the refactored driver API.
test/antithesis/harness/src/payload/dogstatsd/service_checks.rs	Replace `random_choice` usage with `rand` selection APIs and thread RNG through helpers.
test/antithesis/harness/src/payload/dogstatsd/metrics.rs	Same as above; also refactors metric extension selection and value-kind selection.
test/antithesis/harness/src/payload/dogstatsd/events.rs	Same as above for event option selection and field writing.
test/antithesis/harness/src/payload/dogstatsd/common.rs	Make vibe/choice/field helpers RNG-driven and switch selection to `rand` APIs.
test/antithesis/harness/src/payload/dogstatsd.rs	Add byte-limited line/payload writers and proptest invariants for size/newline properties.
test/antithesis/harness/src/driver.rs	Change driver from per-line sends to byte-limited payload datagrams, updating stats semantics.
test/antithesis/harness/proptest-regressions/payload/dogstatsd.txt	Check in proptest regression seed(s) for reproducibility.
test/antithesis/harness/Cargo.toml	Add `proptest` dev-dependency for the new property tests.
Cargo.lock	Record `proptest` being pulled in (via harness dev-deps).

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Copilot

Pull request overview

Copilot reviewed 11 out of 12 changed files in this pull request and generated 4 comments.

Copilot

Pull request overview

Copilot reviewed 12 out of 13 changed files in this pull request and generated 8 comments.

Copilot

Pull request overview

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Copilot

Pull request overview

Copilot reviewed 12 out of 13 changed files in this pull request and generated 9 comments.

This commit updates the harness driver to build dogstatsd to a byte limit, in the manner of datadog/lading. I have been unable to investigate SMPTNG-7611 well owing to the error log emission by Datadog Agent. I've added property tests to assert the payload limit is obeyed, accepting that this means making the dogstatsd generator pure with regard to Rng and may not use antithesis SDK's random_* directly.

dd-octo-sts Bot added the area/test All things testing: unit/integration, correctness, SMP regression, etc. label Jul 2, 2026

blt requested a review from Copilot July 2, 2026 12:53

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blt force-pushed the blt/chore_antithesis_add_pyld25_series_are_not_empty branch from 4b011df to 67ce101 Compare July 2, 2026 13:44

blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 51945fe to 30e11dd Compare July 2, 2026 13:44

blt force-pushed the blt/chore_antithesis_add_pyld25_series_are_not_empty branch from 67ce101 to 7024db6 Compare July 2, 2026 16:57

blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 30e11dd to 7ac69cc Compare July 2, 2026 16:58

blt force-pushed the blt/chore_antithesis_add_pyld25_series_are_not_empty branch from 7024db6 to 9d89983 Compare July 2, 2026 21:11

blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 7ac69cc to 3fe9725 Compare July 2, 2026 21:11

blt force-pushed the blt/chore_antithesis_add_pyld25_series_are_not_empty branch from 9d89983 to d652f5f Compare July 2, 2026 21:40

blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch 2 times, most recently from 5b84354 to 7d5c1d2 Compare July 2, 2026 22:08

blt force-pushed the blt/chore_antithesis_add_pyld25_series_are_not_empty branch from d652f5f to f924078 Compare July 2, 2026 22:08

blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 7d5c1d2 to 0984845 Compare July 2, 2026 22:17

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blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 0984845 to 2452073 Compare July 2, 2026 22:41

blt marked this pull request as ready for review July 2, 2026 22:53

blt requested a review from a team as a code owner July 2, 2026 22:53

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blt force-pushed the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch from 732b36f to 65c8858 Compare July 8, 2026 00:59

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Comment thread test/antithesis/scenarios/general/src/bin/parallel_driver_send_dogstatsd.rs Outdated

Comment thread test/antithesis/scenarios/differential/src/bin/parallel_driver_send_dogstatsd_differential.rs Outdated

Comment thread test/antithesis/harness/src/payload/dogstatsd.rs Outdated

blt changed the base branch from blt/chore_antithesis_add_pyld25_series_are_not_empty to graphite-base/1974 July 8, 2026 19:01

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blt requested a review from tobz July 8, 2026 21:36

tobz approved these changes Jul 9, 2026

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blt merged commit cccc3c7 into main Jul 9, 2026
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blt deleted the blt/chore_antithesis_dogstatsd_line_and_payload_generators branch July 9, 2026 15:04

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Summary

Change Type

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References

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Binary Size Analysis (Agent Data Plane)

✅ Binary size difference within threshold

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Regression Detector (Agent Data Plane)

Optimization Goals: ✅ No significant changes detected

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