Node API Cache Proxy

When API is down, work may be hard for front-end developer. Configure api cache to fallback REST API responses.

“API not responding”

How it works?

• Works as middleware for API calls
• Save responses depending on address, headers and request payload
• Serves cached data, when API is down

How to install

npm install --save node-api-cache-proxy

How to use

Minimal using Express:

var express = require('express')
var APICacheProxy = require('node-api-cache-proxy')

var app = express()
var apiCacheProxy = new APICacheProxy({
	apiUrl: 'http://destination-api-url.com',
	cacheDir: 'cache-api/',
	localURLReplace: function(url) {
		return url.replace('/api/', '/')
	}
})

app.use('/api', apiCacheProxy)

Sample using Express:

var express = require('express')
var APICacheProxy = require('node-api-cache-proxy')

var app = express()
var apiCacheProxy = new APICacheProxy({
	apiUrl: 'http://destination-backend-url.com',
	excludeRequestHeaders: [
		'Cookie', 'User-Agent', 'User-Agent', 'Referer', 'Origin', 'Host', 'DNT'
	],
	excludeRequestParams: ['_'],
	isValidResponse: function(requestEnvelope) {
		// this is default validation function, feel free to override it
		if (requestEnvelope.statusCode === 200) {
			return true;
		} else {
			return false;
		}
	},
	localURLReplace: function(url) {
		return url.replace('/api/', '/')
	}
})

app.use('/api', apiCacheProxy)

API

var apiCache = new APICache(config), config:

• cacheEnabled {boolean}: When false, plugin will work as proxy, without caching.
• apiUrl {string, required}: Proxy replaces protocol, domain part with apiUrl
• cacheDir {string}: Directory to save requests
• excludeRequestHeaders {array}: headers to omit when writing or reading cache file
• excludeRequestParams {array}: usually cache parameter from your request address
• localURLReplace(url: string) {function}: prepare url to API
• isValidResponse {function(requestEnvelope: Object)}: Check if API response is valid or not.
  • when true is returned, request will be saved and ready to use
  • when false is returned, request won’t be saved and cache entry will be served instead (if available)
• timeout {object}: Milliseconds, helps terminating requests for really slow backends.

requestEnvelope format:

	{
		reqURL: 'http://my-api.local/method/route?action=sth',
		reqMethod: 'POST',
		reqHeaders: response.request.headers,
		reqBody: 'request=a&body=is&just=for&POST=PUT,etc:)',

		body: body,
		headers: response.headers,
		statusCode: response.statusCode,
		statusMessage: response.statusMessage,

		cacheDate: "2015-11-30 01:35:53",
		version: "0.6.1"
	}

Error Handling

Custom error handler, executed when API response doesn’t pass isValidResponse test, and there is no cached response:

var apiCache = new APICacheProxy({...})
var app = express()

app.use('/api', function(req, res, next) {
	apiCacheProxy(req, res, next).catch(function(requestEnvelope) {
		res.status(requestEnvelope.statusCode).send(
			'<pre>' + requestEnvelope.body + '</pre>'
		)
	})
})

Handle case, when API response doesn’t pass isValidResponse test but there is cached response:

var apiCache = new APICacheProxy({...})
var app = express()

app.use('/api', function(req, res, next) {
	apiCacheProxy(req, res, next).then(function(status) {
		if (status.dataSource === 'Cache') {
			console.warn('[' + status.envelope.reqMethod + '] ' + status.envelope.reqURL)
			console.warn('  API failure. Served: ' + status.filePath)
		}
	})
})

API data format support table

Requirements

This module is maintained on node v0.12.7. It may work on older and newer node versions. Feel free to test and send me a feedback :-)