import { OnModuleInit, OnModuleDestroy } from '@nestjs/common';
import type Redis from 'ioredis';
/**
 * Lock heartbeat service
 *
 * Provides heartbeat mechanism for distributed lock instances.
 * Each instance sends periodic heartbeats to Redis to indicate it's alive.
 * Dead instances can be detected by checking if their heartbeat has expired.
 *
 * @example
 * ```typescript
 * constructor(private heartbeatService: LockHeartbeatService) {}
 *
 * async isInstanceAlive(instanceId: string): Promise<boolean> {
 *   return this.heartbeatService.isInstanceAlive(instanceId);
 * }
 * ```
 */
export declare class LockHeartbeatService implements OnModuleInit, OnModuleDestroy {
    private readonly logger;
    private readonly instanceId;
    private redis;
    private heartbeatTimer;
    /**
     * Heartbeat interval in milliseconds
     * @default 5000 (5 seconds) - reduced for faster failure detection
     */
    private readonly heartbeatInterval;
    /**
     * Heartbeat TTL in seconds (3x interval for safety)
     * @default 15 (15 seconds) - adjusted to match new interval
     */
    private readonly heartbeatTtl;
    constructor(instanceId?: string);
    onModuleInit(): Promise<void>;
    onModuleDestroy(): Promise<void>;
    /**
     * Set Redis client (required for dependency injection)
     */
    setRedisClient(redis: Redis): void;
    /**
     * Send heartbeat to Redis
     * Stores instance information with TTL
     */
    private sendHeartbeat;
    /**
     * Remove heartbeat record from Redis
     */
    private removeHeartbeat;
    /**
     * Check if an instance is alive by checking its heartbeat
     *
     * @param instanceId - Instance identifier to check
     * @returns True if instance is alive (heartbeat exists), false otherwise
     */
    isInstanceAlive(instanceId: string): Promise<boolean>;
    /**
     * Get heartbeat information for an instance
     *
     * @param instanceId - Instance identifier
     * @returns Heartbeat data or null if not found
     */
    getHeartbeatInfo(instanceId: string): Promise<{
        instanceId: string;
        timestamp: number;
        pid: number;
    } | null>;
    /**
     * Get all active instances (with heartbeat)
     *
     * **Note**: Uses SCAN command to avoid blocking Redis in production.
     *
     * @returns Array of instance IDs that are currently alive
     */
    getActiveInstances(): Promise<string[]>;
    /**
     * Get current instance ID
     */
    getInstanceId(): string;
    private createInstanceId;
}