Concurrent Memoize

Memoize Concurrent Requests in your Application so that only one request is executed and all subsequent, concurrent, waiting requests that are identical to the first request get notified with the result of the first call. Also all future accesses of the value return cache.

Install

npm install concurrent-memoize

Why?

Often times organized, reusable code may make many duplicate calls. These calls may be database queries, HTTP requests, other third party requests. This module de-duplicates asynchronous, simultaneous requests, in this way

1. Check cache. If it exists, return instantly.
2. Check if an identical request is currently executing. If so, wait for the response to that request.
3. If no cache exists and no identical request is executing, then begin executing the request, and when the request is finished executing, notify all concurrent identical requests that are waiting for the same result.

A bit of history

This module was originally created to keep a per request cache of all database queries made during a single HTTP GET request within a REST API. The cache only exists per request, eliminating the problem of stale data since most requests are very short lived. Executing in a GET request ensured that (for the most part) no data in the cache could become stale, since GET requests, by convention, should not make major database modifications anyway (by convention, major database modifications should be done in POST/PUT/etc requests).

Usage

1"use strict";
2
3let cache = {};
4
5const memoize = require('concurrent-memoize');
6
7const request = memoize(require('request'), 'request', {
8  getCache: function() {
9    return cache;
10  },
11  cacheKey: function(opts) {
12    return JSON.stringify(util.parse(opts).pathname);
13  },
14  parseOptions: function(opts, queryOpts) {
15    return queryOpts;
16  },
17  allowCache: function() {
18    return true;
19  }
20});
21
22// ...
23 
24request('http://localhost/')
25  .then(function(err, result) {
26    console.log("I'm fresh!")    
27  });
28request('http://localhost/')
29  .then(function(err, result) {
30    console.log("I'm cached!");
31  });

Early Stage Versioning

The module is in its early stages still, so I'm resetting the major version to 0.x.x in order to work out bugs without increasing the major version with every breaking change.

Documentation

memoize(originalFunc, funcName, config)

This function will return another function that wraps originalFunc. Calling this function will transparently check cache, wait for a result, or execute the query to get the result.

memoize.async(originalFunc, funcName, config)

This function is to be used for functions that expect a callback. The function returned will be "promisified" in that it will work instead with a promise if no callback is passed.

memoize.property(object, funcName, config)

This function is a shortcut to apply the memoize to the property name funcName on the object object. The this is preserved on the overriden function.

memoize.timer

Keeps track of statistics across the lifetime of the process.

memoize.defaultConfig

Contains the base config for a managing cache (see lib/defaultConfig for documentation).

License

ISC