/**
 * Distributed Semaphore
 *
 * Provides concurrency control using the StorageAdapter interface.
 * Each concurrent execution acquires a "ticket" stored in the backend.
 * Active tickets tracked via atomic counter + individual ticket keys with TTL.
 */
import type { StorageAdapter } from '@frontmcp/utils';
import type { SemaphoreTicket } from './types';
export declare class DistributedSemaphore {
    private readonly storage;
    private readonly ticketTtlSeconds;
    constructor(storage: StorageAdapter, ticketTtlSeconds?: number);
    /**
     * Attempt to acquire a concurrency slot.
     *
     * @returns A SemaphoreTicket if acquired, or null if rejected
     * @throws QueueTimeoutError if queued and timeout expires
     */
    acquire(key: string, maxConcurrent: number, queueTimeoutMs: number, entityName: string): Promise<SemaphoreTicket | null>;
    private tryAcquire;
    private release;
    private waitForSlot;
    getActiveCount(key: string): Promise<number>;
    forceReset(key: string): Promise<void>;
}