Incident Dossier

Jitter Can Go Negative

During a coordinated retry storm the on-call team noticed that their jitter helper was producing negative delays for some attempts, which `setTimeout` was silently coercing to 0. The result was that clients synchronized their retries into a single thundering herd wave, exactly when the system needed them spread out.

Initial failing signalSubtractive jitter can produce negative delaysExpected behavior: delay is always >= 0 · actual behavior: delay returns a negative number for jitterMs > baseMs

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Inspect the delay function and ask what happens when jitterMs > baseMs.
Notice that the subtraction can produce negative numbers for any non-zero random value.
Clamp the effective jitter so the subtraction is always non-negative.

Focus Mode

Start

src/jitter.js

Likely area

src/jitter.js

Challenge Coach

Hints reveal broad direction first, then narrow toward the suspect path without showing hidden tests or exact solution code.

TopicReliability

DifficultyMedium

Est. time18 min

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Evidence Map

Failing signal loaded from challenge API
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workspace

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