2q-cache 中文文档教程

发布于 5年前 浏览 24 项目主页 更新于 3年前

2Q cache

用于实现 2Q 缓存算法的 Node.js 和浏览器的简单且可配置的缓存库 (http://www.vldb.org/conf/1994/P439.PDF) 该算法试图保留最常使用的元素,因此它比其他缓存(例如 LRU(最近最少使用)缓存)表现出更好的缓存命中率。

Installation:

npm i 2q-cache

Usage:

const Cache2Q = require('2q-cache');

let cache = new Cache2Q(400); //sets max count of cache elems
/*
    20% of size will be "in" FIFO bucket,
    60% - "out" FIFO bucket,
    20% - "main" LRU cache

    OR

    let cache = new Cache2Q[400, 440, 200] - you also can define manually sizes of each section in cache.
    First element of array is size of "in" FIFO bucket,
    Second - size of "out" FIFO bucket,
    Third - size of "main" LRU cache
*/

带有选项的示例

const Cache2Q = require('2q-cache');

let options = {
    ttl : 1000 * 60 * 60, //default time to delete elements from cache : number
    stringKeys : true, // If stringKeys are true, keys of cache elements will be convert to string by JSON.stringify
    ttlInMain : false, //you can disable time to delete in 'main' section of cache. It can be useful, because in main                           //section stored most requested cache elements
    mainStorageType : 'lfu' //Type of main storage. It can be 'lru' - Least Recently Used,
                            //'mru' - Most Recently used,
                            //'lfu' - Least-Frequently used
}

let cache = new Cache2Q(400, options); //or ([100,200,250], options);

默认情况下

  • cache ttl (lifetime) equals 0, so elements will not be removed by timeout
  • stringKeys are false, so new elements are saving "as is", without using JSON.stringify

您还可以使用 2Q 缓存模块的 Typescript 版本:

import {Cache2Q, CacheException} from '2q-cache/ts/cache2Q';

let cache : Cache2Q = new Cache2Q(400); 

API

  • code>set(key : any, value : any, ttl : number = 0 (optional))

    < 有生命周期(可选) 如果 key 存在,它更新 value 和 ttl 参数 ttl 覆盖默认

  • ttl

  • 设置代码>获取(密钥)=> value

    通过提供的键返回值 不存在,则

  • null

    返回

  • 如果键 ) => boolean

    则返回 true,否则返回 false

  • 存在

  • 如果 删除(键:任何)=> boolean

    从缓存中删除对 (key, value)。 如果元素不存在,则返回 false。

  • mdel(keys : Array) : Array

    与 'del' 相同,但对于键数组

  • resetTtl(key : any, ttl : number)

    通过提供的密钥重置(覆盖)元素的 ttl。

  • mresetTtl(keys : Array)

    与 'resetTtl' 相同,但对于键数组

  • setDefaultTtl(ttl : number)

    设置默认 ttl。

  • setStringifyKeys(param : boolean)

    覆盖字符串化键的默认设置。 如果 stringify 键为真,键将被 JSON.stringify 转换为字符串

  • clear()

    清除缓存

  • alloc(size : number | Array)

    设置新的大小每个缓存部分。 参数与构造函数参数相同。 不允许使最大部分大小更小

  • allocUnsafe(size : number | Array)

    为每个缓存部分设置新的大小。 参数与构造函数参数相同。 允许使最大截面尺寸更小。 如果某些缓存部分的新最大大小小于当前大小,则将删除旧元素。

  • getSize()

    返回对象如下:

    {
        buckets : {
            in : {
                currentSize : 10,
                maxSize : 20
            },
            out : {
                currentSize : 0,
                maxSize : 60
            },
        },
        main : {
            currentSize : 0,
            maxSize : 20
        }
    }

ROADMAP

  • Any ideas?

2Q cache

Simple and configurable cache library for Node.js and Browser that implements 2Q Cache algorithm (http://www.vldb.org/conf/1994/P439.PDF) This algorithm tries to preserve the most used elements, so it demonstrates better cache hit than other caches,for example, LRU (Least Recently Used) cache.

Installation:

npm i 2q-cache

Usage:

const Cache2Q = require('2q-cache');

let cache = new Cache2Q(400); //sets max count of cache elems
/*
    20% of size will be "in" FIFO bucket,
    60% - "out" FIFO bucket,
    20% - "main" LRU cache

    OR

    let cache = new Cache2Q[400, 440, 200] - you also can define manually sizes of each section in cache.
    First element of array is size of "in" FIFO bucket,
    Second - size of "out" FIFO bucket,
    Third - size of "main" LRU cache
*/

Example with options

const Cache2Q = require('2q-cache');

let options = {
    ttl : 1000 * 60 * 60, //default time to delete elements from cache : number
    stringKeys : true, // If stringKeys are true, keys of cache elements will be convert to string by JSON.stringify
    ttlInMain : false, //you can disable time to delete in 'main' section of cache. It can be useful, because in main                           //section stored most requested cache elements
    mainStorageType : 'lfu' //Type of main storage. It can be 'lru' - Least Recently Used,
                            //'mru' - Most Recently used,
                            //'lfu' - Least-Frequently used
}

let cache = new Cache2Q(400, options); //or ([100,200,250], options);

By default

  • cache ttl (lifetime) equals 0, so elements will not be removed by timeout
  • stringKeys are false, so new elements are saving "as is", without using JSON.stringify

You also can use Typescript version of 2Q cache module:

import {Cache2Q, CacheException} from '2q-cache/ts/cache2Q';

let cache : Cache2Q = new Cache2Q(400); 

API

  • set(key : any, value : any, ttl : number = 0 (optional))

    Sets new pair (key, value) with lifetime (optional) if key exists, it updates value and ttl parameter ttl overrides default ttl settings

  • mset(Array<object {key : any, value : any, ttl : number = 0}>)

    the same as 'set', but for array of new elements

  • get(key) => value

    Returns value by presented key if key doesn't exists, returns null

  • mget(Array<key : any>) : Array<values : any>

    the same as 'get', but for array of keys

  • has(key) => boolean

    Returns true if key exists, otherwise returns false

  • mhas(Array<key : any>) : Array<boolean>

    the same as 'has', but for array of keys

  • delete(key : any) => boolean

    deletes pair (key, value) from cache. If element doesn't exists, returns false.

  • mdel(keys : Array<any>) : Array<boolean>

    the same as 'del', but for array of keys

  • resetTtl(key : any, ttl : number)

    resets (overrides) ttl for element by presented key.

  • mresetTtl(keys : Array<object {key : any, ttl : number}>)

    the same as 'resetTtl', but for array of keys

  • setDefaultTtl(ttl : number)

    sets default ttl.

  • setStringifyKeys(param : boolean)

    overrides default setting for stringify keys. if stringify keys are true, keys will be converted to string by JSON.stringify

  • clear()

    Clears cache

  • alloc(size : number | Array<number>)

    Sets new size for each cache section. Parameter same as constructor parameter. Doesn't allow make max section size smaller

  • allocUnsafe(size : number | Array<number>)

    Sets new size for each cache section. Parameter same as constructor parameter . Allow make max section size smaller. If new max size smaller than current size on some cache section, older elements will be removed.

  • getSize()

    Returns object like this:

    {
        buckets : {
            in : {
                currentSize : 10,
                maxSize : 20
            },
            out : {
                currentSize : 0,
                maxSize : 60
            },
        },
        main : {
            currentSize : 0,
            maxSize : 20
        }
    }

ROADMAP

  • Any ideas?
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