Narcoleptic Programmers' Medicine

    exp-asynccache

    3.1.0 • Public • Published

    asynccache

    An async cache with a lookup function per key for node js with a different interface than async-cache.

    Errors are not cached and the callback function is always called asynchronously even if the value is resolved synchronously.

    Installation

    npm install --save exp-asynccache

    Usage

    Callback usage:

    var AsyncCache = require("exp-asynccache");
    var cache = new AsyncCache();
    
    cache.lookup("foo", function (resolve) {
      // Find foo asynchronously (or synchronously) then call resolve with the value
      resolve(null, "baz");
    }, function (err, value) {
      console.log(value); // value will be "baz"
    });

    Promise usage:

    var AsyncCache = require("exp-asynccache");
    var cache = new AsyncCache();
    
    var hit = cache.lookup("foo", function (resolve) {
      resolve(null, "baz");
    });
    
    hit.then(function (value) {
      console.log(value); // value will be "baz"
    });

    By default a lru-cache-plus cache with default settings is used to store cached objects but you can provide your own.

    var AsyncCache = require("exp-asynccache");
    var LRU = require("lru-cache-plus"); // any lru-cache compatible cache will do
    
    var cache = new AsyncCache(new LRU({
      max: 500,
      maxAge: 1000 * 60 * 60
    }));

    The resolve function can take more arguments than error and key. It will pass these to the underlying cache's set method. So when using lru-cache-plus you can provide a max age per key:

    var AsyncCache = require("exp-asynccache");
    var cache = new AsyncCache();
    
    cache.lookup("foo", function (resolve) {
      resolve(null, "baz", 1000); // Let foo live for one second
    });

    Cache interface

    The undelying cache should adhere to the same interface as LRUCache:

    get(key)        -> lookup value. undefined return value indicates cache miss.
    set(key, value) -> set value
    has(key)        -> return true if key exists
    
    

    If the cache impmlemntation is asynchronous, promises can be returned

    Warning

    Don't use more data from the closure than what is used to construct the cache key:

    var AsyncCache = require("exp-asynccache");
    var cache = new AsyncCache();
    
    function getPerson(name, location, callback) {
    
      cache.lookup(name, function (resolve) { // <-- Only name is used
    
        personRepo.get(name, location, resolve); // <-- Both name and location is used
    
      }, callback);
    
    }

    In the above example there might be several different objects returned by personRepo for the same name but with different locations but they are all cached only by the name. The correct code would be to construct the cache key from both name and location.

    Keywords

    Install

    npm i exp-asynccache

    DownloadsWeekly Downloads

    387

    Version

    3.1.0

    License

    MIT

    Unpacked Size

    7.92 kB

    Total Files

    4

    Last publish

    Collaborators

    • andolf
    • markusn
    • linuss
    • joelabrahamsson
    • norla
    • paed01
    • indeedshouts
    • jonaswalden
    • marcusgronblad
    • gabrielf
    • theneubeck
    • nordbergm