chore(antithesis): non-utf8 bytes payloads represent 1% of generation by blt · Pull Request #2217 · DataDog/saluki

blt · 2026-07-27T22:59:58Z

Summary

ADP and Datadog Agent deal with non-utf8 bytes differently. The way that
intake accepts non-utf8 bytes varies depending on where in the payload they
appear and for which protocol version. Previously I created payloads that were
too non-utf8 heavy, meaning most payloads could be rejected by intake. This
commit changes the generator to emit non-utf8 bytes into about 1% of payloads.

Change Type

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

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References

The essential property we want to determine is whether ADP-on/ADP-off emits payloads to intake API that the intake API rejects. This is especially of interest for inputs that we know are ultimately rejected by intake API -- non-utf8 bytes in the wrong spot -- but are _not_ rejected by the SUT. The old mechanism had a feral/clean 'vibe' which served for a while but was confusing to debug. Is feral malformed? Is feral well-formed but wild? Anyway I got tired of it. There's now a predicate which defines whether a payload is well-formed or not -- that is, accepted by ADP-off Datadog Agent -- independent of whether intake API ultimately accepts the payloads that ingress inspires. Later I will build a generator that only emits malformed ingress but that is only hinted at in this work.

blt · 2026-07-27T23:00:11Z

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datadog-prod-us1-6 · 2026-07-27T23:02:13Z

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pr-commenter · 2026-07-27T23:07:57Z

Binary Size Analysis (Agent Data Plane)

Baseline: e34c659 · Comparison: 43cf97d · diff
Analysis Configuration: stripped binaries · Pass/Fail Threshold: +5%
Sizes: 41.09 MiB (baseline) vs 41.09 MiB (comparison)
Size Change: +0 B (+0.00%)

✅ Binary size difference within threshold

Changes by Module

Module	File Size	Symbols
`anon.44a0faa3240fa409baa379409d152aec.1.llvm.2649486637407723024`	+129 B	1
`anon.44a0faa3240fa409baa379409d152aec.1.llvm.4920541009509882327`	-129 B	1
`anon.44a0faa3240fa409baa379409d152aec.4.llvm.2649486637407723024`	+113 B	1
`anon.44a0faa3240fa409baa379409d152aec.4.llvm.4920541009509882327`	-113 B	1
`anon.44a0faa3240fa409baa379409d152aec.3.llvm.2649486637407723024`	+108 B	1
`anon.44a0faa3240fa409baa379409d152aec.3.llvm.4920541009509882327`	-108 B	1
`anon.44a0faa3240fa409baa379409d152aec.0.llvm.2649486637407723024`	+96 B	1
`anon.44a0faa3240fa409baa379409d152aec.0.llvm.4920541009509882327`	-96 B	1
`anon.44a0faa3240fa409baa379409d152aec.2.llvm.2649486637407723024`	+94 B	1
`anon.44a0faa3240fa409baa379409d152aec.2.llvm.4920541009509882327`	-94 B	1

Detailed Symbol Changes

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [NEW]    +129  [NEW]     +40    anon.44a0faa3240fa409baa379409d152aec.1.llvm.2649486637407723024
  [NEW]    +113  [NEW]     +24    anon.44a0faa3240fa409baa379409d152aec.4.llvm.2649486637407723024
  [NEW]    +108  [NEW]     +19    anon.44a0faa3240fa409baa379409d152aec.3.llvm.2649486637407723024
  [NEW]     +96  [NEW]      +7    anon.44a0faa3240fa409baa379409d152aec.0.llvm.2649486637407723024
  [NEW]     +94  [NEW]      +5    anon.44a0faa3240fa409baa379409d152aec.2.llvm.2649486637407723024
  [DEL]     -94  [DEL]      -5    anon.44a0faa3240fa409baa379409d152aec.2.llvm.4920541009509882327
  [DEL]     -96  [DEL]      -7    anon.44a0faa3240fa409baa379409d152aec.0.llvm.4920541009509882327
  [DEL]    -108  [DEL]     -19    anon.44a0faa3240fa409baa379409d152aec.3.llvm.4920541009509882327
  [DEL]    -113  [DEL]     -24    anon.44a0faa3240fa409baa379409d152aec.4.llvm.4920541009509882327
  [DEL]    -129  [DEL]     -40    anon.44a0faa3240fa409baa379409d152aec.1.llvm.4920541009509882327
  [ = ]       0  [ = ]       0    TOTAL

datadog-prod-us1-6

More details

The new injection is bounded to one byte per datagram, preserves the existing size and forwarding invariants, and excludes event and service-check lines from metric-name mutation. No diff-only behavioral regression was identified; runtime confirmation was blocked by unavailable Rust dependencies in the sandbox.

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pr-commenter · 2026-07-27T23:27:32Z

Regression Detector (Agent Data Plane)

Run ID: 516332f6-3eb1-4379-a670-deeecef04134
Baseline: e34c659f · Comparison: 43cf97d2 · diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment (3)

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_idle	memory	⚪ +0.30	metrics profiles logs
quality_gates_rss_dsd_low	memory	⚪ +0.29	metrics profiles logs
quality_gates_rss_dsd_medium	memory	⚪ +0.21	metrics profiles logs

Bounds Checks: ✅ Passed (3)

experiment	check	replicates	observed	links
quality_gates_rss_dsd_low	memory_usage	10/10	✅ 45.4 MiB ≤ 50 MiB	metrics profiles logs
quality_gates_rss_dsd_medium	memory_usage	10/10	✅ 67.1 MiB ≤ 75 MiB	metrics profiles logs
quality_gates_rss_idle	memory_usage	10/10	✅ 31.2 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.

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chatgpt-codex-connector · 2026-07-27T23:27:39Z

+/// Aberrant identifier segments: whitespace, NUL, and exotic but valid UTF-8. Invalid-UTF-8 bytes are
+/// deliberately absent. The per-datagram injection in `write_payload` adds one at a fixed rate rather
+/// than sprinkling them per segment, so their blast radius stays a budgeted fraction of datagrams
+/// instead of compounding across every minted context into a near-certain whole-payload v3 reject.


Preserve non-UTF-8 coverage across sampled fields

Removing invalid bytes from ABERRANT_WORD means every shared field builder now produces valid UTF-8, while the replacement injection always inserts at the start of a metric line. Consequently, runs can no longer exercise non-UTF-8 tags, set values, event fields, or service-check fields, even though these fields take different intake paths (for example, v3 tag dictionaries are sanitized while name dictionaries reject the payload). Keep the one-per-datagram budget, but sample the injection target among the eligible fields so this differential harness retains the position-dependent coverage described by the change.

AGENTS.md reference: test/antithesis/AGENTS.md:L86-L90

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This was referenced Jul 27, 2026

chore(antithesis): Intro Intake V3 #2214

Open

chore(antithesis): Alter dogstatsd generation to is_malformed regime #2215

Open

This was referenced Jul 27, 2026

chore(antithesis): Bound contexts in runs #2216

Open

chore(antithesis): Add provider_kind in sample config #2218

Open

dd-octo-sts Bot added the area/test All things testing: unit/integration, correctness, SMP regression, etc. label Jul 27, 2026

blt changed the title ~~chore(antithesis): is_malformed based load generation~~ chore(antithesis): non-utf8 bytes payloads represent 1% of generation Jul 27, 2026

blt marked this pull request as ready for review July 27, 2026 23:24

blt requested review from a team as code owners July 27, 2026 23:24

datadog-prod-us1-6 Bot reviewed Jul 27, 2026

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chatgpt-codex-connector Bot reviewed Jul 27, 2026

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blt mentioned this pull request Jul 28, 2026

chore(antithesis): Frechet Distance and intake rework #2228

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chore(antithesis): non-utf8 bytes payloads represent 1% of generation - #2217

chore(antithesis): non-utf8 bytes payloads represent 1% of generation#2217
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⚠️ Warnings

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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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blt commented Jul 27, 2026 •

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