Express CLS Context

CLS based context for Express Requests

Installation

$ npm install @parthar/express-cls-context --save

Usage

// setup expressjs middleware
var expressCls = require("@parthar/express-cls-context");
var express = require("express");
var app = express();
...
app.use(expressCls.middleware);
// everything after this has access to the context via setContext & getContext

// e.g., set the user-context after-login
app.post('/login',
    passport.authenticate('local'),
    function (req, res) {
        expressCls.setContext('user', req.user);
    }
);
// or, after deserialization of session
passport.deserializeUser(function(id, done) {
    User.findById(id, function(err, user) {
        expressCls.setContext('user', user);
        done(err, user);
    });
});

// access the user somewhere deep within some user-service
function someService(arg1, arg2, callback) {
    var user = expressCls.getContext('user');
}

// get the CLS namespace to bind to a function
// this is sometimes needed for code that does not comply to CLS
// e.g., refer https://github.com/Automattic/mongoose/issues/3313
function saveUser(data, callback) {
    var user = expressCls.getContext('user');
    var clsCallback = expressCls.getNamespace().bind(callback);
    mongooseModel.save(clsCallback);
}