51Degrees Pipeline Node.js  4.1

51Degrees Pipeline for Node.js


This example demonstrates how to add a cache to an aspect engine.The fiftyone.pipeline.engines module comes with an implementation of a Least Recently Used (lru) cache that can be used in place of the custom cache created in this example.

To construct the lru cache pass in a size (in entries) parameter to its constructor.

let lruCache = new engine.lruCache(100);

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const pipeline = require('fiftyone.pipeline.core');
// Note that this example is designed to be run from within the
// source repository. If this code has been copied to run standalone
// then you'll need to replace the require below with the commented
// out version below it.
const engine = require('..');
// const engine = require("fiftyone.pipeline.engines");
// This is a very simple cache that uses an in memory JavaScript object
class MyCustomCache extends engine.DataKeyedCache {
constructor (size) {
this.cache = {};
get (cachekey) {
if (this.cache[cachekey]) {
// Log out whether something has been fetched
// from cache to demonstrate the example
console.log('Fetched from cache');
return this.cache[cachekey];
put (cachekey, value) {
this.cache[cachekey] = value;
// A custom engine to test the caching, note the instance of the
// evidenceKeyFilter class which is used to determine which evidence
// is used by the flowElement and in turn the pipeline.
const cacheTest = new engine.Engine({
dataKey: 'cacheTest',
cache: new MyCustomCache(),
evidenceKeyFilter: new pipeline
processInternal: function (flowData) {
const engine = this;
return new Promise(function (resolve, reject) {
const data = new pipeline
{ flowElement: engine, contents: { hello: 'world' } });
properties: {
hello: {
type: 'string'
const cachePipeline = new pipeline.PipelineBuilder().add(cacheTest).build();
const flowData = cachePipeline.createFlowData();
const processFlowDataWithUserId = function (userID) {
flowData.evidence.add('cookie.my-user-id', userID);
return flowData.process();
// Run the same evidence through the pipeline twice,
// second time should be fetched from the cache
processFlowDataWithUserId('112').then(() => processFlowDataWithUserId('112'));