@accedo/accedo-one-express NPM

The Accedo One Express middleware

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Summary

This is the official Accedo One middleware for Express.

The Accedo One SDK for Javascript(https://github.com/Accedo-Products/accedo-one-sdk-js/) provides an easy way to make use of Accedo One APIs. This middleware provides additional benefits and makes things even easier in the context of an Express app.

We follow semantic versioning, and you may have a look at our change log here.

Compatibility

This middleware is written in ES6 (with CommonJS modules rather than ES6 Modules).

This should work from version 4, but we test on, and recommend to use the latest LTS version of Node (currently Node 6, soon Node 8).

For earlier Node versions, you may try introducing a compilation step to ES5 (through Babel or Buble, for instance). Note we did not test this and strongly suggest not using a deprecated Node version as they may lack important security fixes.

Regarding Express, we support and test against version 4.

Features

Features inherited from the Accedo One SDK for Javascript :

easy access to Accedo One APIs
automatic deviceId creation when none was provided
automatic session creation when none was provided (lazy - only when needed)
automatic session re-creation when the existing one has expired (lazy)
ensures only one session will be created at a time, even if a request triggers concurrent Accedo One calls

Extra features provided by this Express middleware :

automatic creation of Accedo One client instances for each request, attached to the response object for further use
automatically passes the requester's IP onto Accedo One calls for analytics and geolocated services
automatic reuse of the deviceId through cookies (can be customized to use anything else based on requests)
automatic reuse of the sessionKey through cookies (can be customized to use anything else based on requests)

Note when you use the middleware, you should also configure Express to handle proxies correctly as we rely on the IP it gives us. Do read the Express doc, and the note on this further below.

For instance: app.set('trust proxy', ['loopback', 'linklocal', 'uniquelocal'])

Documentation

What	Link
The Accedo One Express middleware (this project)	https://accedo-products.github.io/accedo-one-sdk-express/
The Accedo One JS SDK	https://accedo-products.github.io/accedo-one-sdk-js/
The Accedo One REST APIs	https://developer.one.accedo.tv

Each Express response gets associated to an Accedo One client instance, found in res.locals.accedoOneClient (when res is the response variable name).

To find what methods are available on these instances, refer to the API docs for the Accedo One JS SDK listed above.

The doc for the REST APIs is also listed as Accedo One-specific terminology is defined there.

Installation

Your preferred CLI tool	Command
Yarn	`yarn add @accedo/accedo-one @accedo/accedo-one-express`
NPM	`npm install --save @accedo/accedo-one @accedo/accedo-one-express`

Then you can get the default export to use the middleware:

Method	Code
CommonJS	const accedoOne = require('@accedo/accedo-one-express')
ES6 Module	import accedoOne from '@accedo/accedo-one-express'

Examples

Use the middleware to persist deviceId and sessionKey via cookies

const accedoOne = require('@accedo/accedo-one-express');
const express = require('express');

const PORT = 3000;

express()
// handle proxy servers if needed, to pass the user's IP instead of the proxy's. Read more about this further.
.set('trust proxy', ['loopback', 'linklocal', 'uniquelocal'])
// place the accedoOne middleware before your request handlers
.use(accedoOne({ appKey: '56ea6a370db1bf032c9df5cb' }))
.get('/test', (req, res) => {
   // access your client instance, it's already linked to the deviceId and sessionKey via cookies
   res.locals.accedoOneClient.getEntryById('56ea7bd6935f75032a2fd431')
   .then(entry => res.send(entry))
   .catch(err => res.status(500).send('Failed to get the result'));
})
.listen(PORT, () => console.log(`Server is on ! Try http://localhost:${PORT}/test`));

See also examples in the documentation linked above.

SDK development

Clone/fork this repo
Run yarn (install it first if needed)
Develop !
Before pushing, remember to:
- add tests and check they all pass (npm test)
- document any public API with JSDoc comments and generate the new doc (npm run doc)

More information & Links

On the Express `trust proxy` setting, and propagating the right IP

This middleware will set the incoming request IP (let's call it ∑) in the x-forwarded-for (XFF) header, when sending requests to Accedo One. The value of ∑ is what Express decides is the user’s IP.

1/ Express just acts normally when no trust proxy is set, using the incoming connection IP. So it sets ∑ to the proper IP on direct user access, and the proxy (or CDN, or such)'s IP when the user went through that.

You want to avoid reporting any proxy's IP, because it would prevent Accedo One's analytics and geolocation features from working reliably.

2/ When setting trust proxy to true (or enabling it, which does the same thing), the behaviour changes. Now, the value of ∑ will be the first value given in the incoming request's XFF header. “First value” is the left-most value. So what we are saying is that we trust every single proxy, and whatever ends up in XFF is trusted, so we pick the value that was first set (which is the user's IP when everybody plays nice and respects that order). Also note, if there is no XFF header, then the connection’s IP is used as a fallback (that’s good ! it means we can handle both CDN and direct connections).

3/ When setting trust proxy to a CSV or array of IPs, those IPs are the proxies we trust. So Express looks at the XFF's right-most IP that does not match any of those trusted proxy: this would be the first “untrusted” IP, and we consider that anything that comes before that is garbage. In that case, the right-most untrusted IP is used as the value of ∑. Here again, if there’s no XFF, the connection IP is used.

In conclusion, we recommend setting the trust proxy value to trust loopback, linklocal, uniquelocal, AND all IPs that are part of your proxying / CDN network ahead of the server running accedo-one-express. Depending on your infrastructure, it may sometimes be more suitable to just set the trust proxy setting to true, or to use a custom function to recover the proper IP with a custom strategy.