Jitter Can Go Negative Debugging Lab

Jitter Can Go NegativeReliabilityMediumPreparing workspaceAutosaved

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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 delay is always >= 0 · received 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

Progressive hints

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

TopicReliability

DifficultyMedium

Est. time18 min

Workspacecreating

Explorer

Preparing workspace files…

Evidence Map

Failing signal loaded from challenge API
Workspace files loaded from workspace API
Results rendered only after API run/submit

Autosaved

workspace

Outputread-onlyready$ workspace boot

Workspace booting...