import type { ConnectionParams } from '@clickhouse/client-common';
import type { TcpConnectionExtra } from './tcp_connection';
import { TcpConnection } from './tcp_connection';
export declare class TcpConnectionPool {
    private idle;
    private active;
    private waitQueue;
    private maxConnections;
    private params;
    private extra;
    private closed;
    private idleTimeout;
    private sweepTimer;
    constructor(params: ConnectionParams, extra?: TcpConnectionExtra);
    acquire(timeout?: number): Promise<TcpConnection>;
    release(conn: TcpConnection): void;
    private sweepIdle;
    close(): Promise<void>;
    get stats(): {
        idle: number;
        active: number;
        waiting: number;
        total: number;
    };
}