/// <reference types="node" />
import { PendingOperation } from './PendingOperation';
import { Resource } from './Resource';
export interface PoolOptions<T> {
    create: CallbackOrPromise<T>;
    destroy: (resource: T) => any;
    min: number;
    max: number;
    acquireTimeoutMillis?: number;
    createTimeoutMillis?: number;
    destroyTimeoutMillis?: number;
    idleTimeoutMillis?: number;
    createRetryIntervalMillis?: number;
    reapIntervalMillis?: number;
    log?: (msg: string) => any;
    validate?: (resource: T) => boolean;
    propagateCreateError?: boolean;
}
export declare class Pool<T> {
    protected min: number;
    protected max: number;
    protected used: Resource<T>[];
    protected free: Resource<T>[];
    protected pendingCreates: PendingOperation<T>[];
    protected pendingAcquires: PendingOperation<T>[];
    protected interval: NodeJS.Timer | null;
    protected destroyed: boolean;
    protected propagateCreateError: boolean;
    protected idleTimeoutMillis: number;
    protected createRetryIntervalMillis: number;
    protected reapIntervalMillis: number;
    protected createTimeoutMillis: number;
    protected destroyTimeoutMillis: number;
    protected acquireTimeoutMillis: number;
    protected log: (msg: string, level: 'warn') => any;
    protected creator: CallbackOrPromise<T>;
    protected destroyer: (resource: T) => any;
    protected validate: (resource: T) => boolean;
    constructor(opt: PoolOptions<T>);
    numUsed(): number;
    numFree(): number;
    numPendingAcquires(): number;
    numPendingCreates(): number;
    acquire(): PendingOperation<T>;
    release(resource: T): boolean;
    isEmpty(): boolean;
    check(): void;
    destroy(): Promise<import("./PromiseInspection").PromiseInspection<{}> | import("./PromiseInspection").PromiseInspection<void>>;
    _tryAcquireOrCreate(): void;
    _hasFreeResources(): boolean;
    _doAcquire(): void;
    _canAcquire(): boolean;
    _validateResource(resource: T): boolean;
    _shouldCreateMoreResources(): boolean;
    _doCreate(): void;
    _create(): PendingOperation<T>;
    _destroy(resource: T): Promise<any>;
    _logError(err: Error): void;
    _startReaping(): void;
    _stopReaping(): void;
}
export declare type Callback<T> = (err: Error | null, resource: T) => any;
export declare type CallbackOrPromise<T> = (cb: Callback<T>) => any | (() => Promise<T>);