index.js

'use strict';

const cls = require('cls-hooked');

const nsid = 'a6a29a6f-6747-4b5f-b99f-07ee96e32f88';

/** Express.js middleware that is responsible for initializing the context for each request. */
function middleware(req, res, next) {
	const ns = cls.getNamespace(nsid) || cls.createNamespace(nsid);
	ns.run(() => next());
}

/**
 * Gets a value from the context by key.  Will return undefined if the context has not yet been initialized for this request or if a value is not found for the specified key.
 * @param {string} key
 */
function get(key) {
	const ns = cls.getNamespace(nsid);
	if (ns && ns.active) {
		return ns.get(key);
	}
}

/**
 * Adds a value to the context by key.  If the key already exists, its value will be overwritten.  No value will persist if the context has not yet been initialized.
 * @param {string} key 
 * @param {*} value 
 */
function set(key, value) {
	const ns = cls.getNamespace(nsid);
	if (ns && ns.active) {
		return ns.set(key, value);
	}
}

module.exports = {
	middleware,
	get: get,
	set: set
}