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Generic cell rate algorithm limiter: idle time banks unlimited credit · case 02

After a quiet period the limiter admits an unbounded burst because TAT lags far behind now.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

Input {period_ms T, burst B, requests [[t, quantity]]}. State TAT starts at 0. A quantity above B is ["never", 0, 0]. Otherwise tat = max(TAT, t) and new_tat = tat + q*T; the request is allowed iff new_tat - t <= B*T, in which case TAT = new_tat and remaining = floor((B*T - (TAT - t))/T). A denied request leaves TAT unchanged and reports retry_after = new_tat - B*T - t and remaining floor((B*T - (tat - t))/T). Return [[decision, retry_after, remaining]].

Why this case matters

GCRA limiters store a single theoretical-arrival timestamp per key; every decision and header value is derived from it, so small formula errors leak bursts or starve clients.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
idle credit bounded	`[["allow", 0, 2], ["allow", 0, 201], ["allow", 0, 200], ["allow", 0, 199], ["allow", 0, 198], ["allow", 0, 197]]`	`[["allow", 0, 2], ["allow", 0, 2], ["allow", 0, 1], ["allow", 0, 0], ["deny", 50, 0], ["deny", 30, 0]]`	Failed

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