import type { Context } from '../context.js';
export interface BackendInstance {
    url: string;
    weight?: number;
    healthy: boolean;
    connections: number;
    responseTime: number;
}
export interface LoadBalancerOptions {
    backends: BackendInstance[];
    strategy?: 'round-robin' | 'least-connections' | 'weighted-round-robin' | 'least-response-time';
    healthCheckInterval?: number;
    healthCheckTimeout?: number;
    maxRetries?: number;
}
export declare class LoadBalancer {
    private backends;
    private strategy;
    private currentIndex;
    private healthCheckInterval;
    private healthCheckTimeout;
    private maxRetries;
    private intervalId;
    constructor(options: LoadBalancerOptions);
    start(): void;
    stop(): void;
    getBackend(): Promise<BackendInstance | null>;
    private getRoundRobinBackend;
    private getLeastConnectionsBackend;
    private getWeightedRoundRobinBackend;
    private getLeastResponseTimeBackend;
    private startHealthChecks;
    private checkHealth;
    updateBackendStats(backend: BackendInstance, responseTime: number, success: boolean): void;
    getStats(): {
        backends: {
            url: string;
            healthy: boolean;
            connections: number;
            responseTime: number;
            weight: number | undefined;
        }[];
        strategy: string;
        totalConnections: number;
    };
}
export declare function loadBalancerPlugin(options: LoadBalancerOptions): (ctx: Context, next: () => Promise<any>) => Promise<void>;
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