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Merge pull request #870 from codingtwinky/promisify_cache
Promisify cache.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,36 +1,75 @@ | ||
| 'use strict'; | ||
| const Bluebird = require('bluebird'); | ||
| const NodeCache = require('node-cache'); | ||
| const cache = Bluebird.promisifyAll(new NodeCache({ stdTTL: 0, errorOnMissing: true })); | ||
| const md5 = require('blueimp-md5'); | ||
| const funcMap = {}; // Will there ever be a use case where this is a cache with TTL? func registration with TTL? | ||
|
|
||
| const signals = require('signals'); | ||
| /** | ||
| * @function resolveFunc | ||
| * @description Get cached result associated with the key or execute a function to get the result | ||
| * @param {string} [key] - A key associated with a function to be executed. | ||
| * @return {Promise} - Promise either resolved with cached result of the function or rejected with function not found. | ||
| */ | ||
| cache.resolveFunc = (key) => { | ||
| return cache.getAsync(key) // Cant do `cache.getAsync(key, true)` due to `get` argument ordering... | ||
| .catch({ errorcode: "ENOTFOUND" }, (e) => { | ||
| if (!funcMap[key]) throw e; // func associated with key is not found, throw not found error | ||
| const result = funcMap[key].func(); // func is found, resolve, set with TTL and return result | ||
| return cache.setAsync(key, result, funcMap[key].ttl) | ||
| .then(() => { return result }); | ||
| }); | ||
| } | ||
|
|
||
| // Wraps a function to produce one value at a time no matter how many times invoked, and cache that value until invalidated | ||
| module.exports = (constructValue) => { | ||
| let constructDone; | ||
| let hasCache = false; | ||
| /** | ||
| * @function registerFunc | ||
| * @description Register a function to cache it's result. If same key exists, key is deregistered and registered again. | ||
| * @param {ttl} [ttl=0] - ttl in seconds to be used for the cached result of function. | ||
| * @param {string} [key=md5 of func] - Key to retrive cached function result. | ||
| * @param {function} [func] - Function to be executed to get the result. | ||
| * @return {string} - key to retrive cached function result. | ||
| */ | ||
| cache.registerFunc = (...args) => { | ||
| let func = args.pop(); | ||
| let key = args.pop() || md5(func); | ||
| let ttl = args.pop() || cache.options.stdTTL; | ||
|
|
||
| let f = (callback) => { | ||
| if (hasCache) return callback(f.error, f.value); | ||
| if (constructDone) return constructDone.add(callback); | ||
| if (typeof func !== "function") { | ||
| throw new Error("no function was passed in."); | ||
| } | ||
|
|
||
| constructDone = new signals.Signal(); | ||
| let localConstructDone = constructDone; | ||
| constructDone.add((err, val) => { | ||
| constructDone = null; | ||
| callback(err, val); | ||
| }); | ||
| constructValue((err, value) => { | ||
| hasCache = true; | ||
| f.error = err; | ||
| f.value = value; | ||
| localConstructDone.dispatch(err, value); | ||
| }); | ||
| }; | ||
| if (isNaN(ttl) || ttl < 0) { | ||
| throw new Error("ttl value is not valid."); | ||
| } | ||
|
|
||
| if (funcMap[key]) { | ||
| cache.deregisterFunc(key); | ||
| } | ||
|
|
||
| f.invalidate = () => { | ||
| hasCache = false; | ||
| f.error = null; | ||
| f.value = null; | ||
| constructDone = null; | ||
| }; | ||
| funcMap[key] = { | ||
| func: func, | ||
| ttl: ttl | ||
| } | ||
|
|
||
| return f; | ||
| return key; | ||
| } | ||
|
|
||
| /** | ||
| * @function invalidateFunc | ||
| * @description Immediately invalidate cached function result despite ttl value | ||
| * @param {string} [key] - A key associated with a function to be executed. | ||
| */ | ||
| cache.invalidateFunc = (key) => { | ||
| cache.del(key); | ||
| } | ||
|
|
||
| /** | ||
| * @function deregisterFunc | ||
| * @description Remove function registration and invalidate it's cached value. | ||
| * @param {string} [key] - A key associated with a function to be executed. | ||
| */ | ||
| cache.deregisterFunc = (key) => { | ||
| cache.invalidateFunc(key); | ||
| delete funcMap[key]; | ||
| } | ||
|
|
||
| module.exports = cache; |
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