/**
 * Cross-replica per-key request rate limiter ([ref] P0-2) — a thin {@link RateGate} over the shared
 * {@link WriteBehindCounter}. Like the in-memory {@link RateLimiter}, `check` both COUNTS the request
 * and decides; here the count is summed fleet-wide via atomic write-behind aggregation.
 *
 * **SOFT limiting** (the WriteBehindCounter is eventually consistent): a replica may briefly admit a few
 * requests over the ceiling at a window boundary before peers' counts propagate. That is fine for a
 * fairness / hot-caller cap (the use case here). A HARD global cap would need a linearizable CAS, not
 * write-behind — same trade as the cross-replica circuit breaker and cost quota.
 */
import type { Pool } from "mysql2/promise";
import type { RateDecision, RateGate, RateLimits } from "../observability/rate-limit.js";
import { type CounterDegradeHook } from "./write-behind-counter.js";
export declare class TiDBRateLimiter implements RateGate {
    private readonly counter;
    /** 🔴 [ref]:限额是比较参数、不是行状态(SQL 腿的行里只有计数),所以换代只动它,库里一行都不用碰。 */
    private limit;
    /** 装配点表达过的运维意图(「这条腿该有刷新环」)。关断哨兵靠它把环真正停掉/重开 —— 0 态零 SQL。 */
    private refreshRequested;
    private refreshIntervalMs;
    constructor(pool: Pool, limit: number, windowMs?: number, now?: () => number, onDegraded?: CounterDegradeHook, queryTimeoutMs?: number);
    setLimits(next: RateLimits): void;
    /** off ⇒ 停环(零 SQL);on 且装配点要过环 ⇒ 起环(幂等,counter 内部 `??=`)。 */
    private syncRefresh;
    check(key: string): RateDecision;
    /** The flush loop self-reaps old windows; the periodic sweeper has nothing to do for this backend. */
    sweep(): void;
    flush(): Promise<void>;
    refresh(): Promise<void>;
    startRefresh(intervalMs?: number): this;
    stop(): void;
}
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