http-proxy-middleware not proxying requests if placed after cookieparser - node.js

Question

The middleware works properly if placed before the cookie parser.But
the session becomes undefined.
If i move the proxy middleware after the cookie parser it does not
proxy requests silently fails without any errors.I tried creating a post request but nothing happens.
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var session = require('express-session');
var cors = require('cors');
var redis = require('redis');
var redisClient = redis.createClient();
var RedisStore = require('connect-redis')(session);
var proxy = require('http-proxy-middleware');
var config = require('config');
var index = require('./routes/index');
var users = require('./routes/users');
var app = express();
var sessionMiddleware = session({
store: new RedisStore({
client:redisClient
}),
secret: 'keyboard cat',
resave: false,
saveUninitialized: true
});
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'hbs');
app.use(sessionMiddleware);
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
//cookie parser
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/bower_components', express.static(__dirname + '/bower_components'));
app.use(cors());
//proxy middleware
app.use('/api', proxy({
target: 'http://localhost:4000',
changeOrigin: true,
onProxyReq: function (proxyReq, req, res) {
proxyReq.setHeader('USER_ID', req.session.user_id);
proxyReq.setHeader('TOKEN',config.get('token'));
}
}));
app.use('/', index);
app.use('/users', users);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handler
app.use(function(err, req, res, next) {
// set locals, only providing error in development
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
// render the error page
res.status(err.status || 500);
res.render('error');
});
module.exports = app;
http-proxy-middleware npm module middleware
app.use('/api', proxy({
target: 'http://localhost:4000',
changeOrigin: true,
onProxyReq: function (proxyReq, req, res) {
proxyReq.setHeader('USER_ID', req.session.user_id);
proxyReq.setHeader('TOKEN',config.get('token'));
}
}));

Answer 1

If you are keeping any parser middlewares, It will format your request, which is not expected by http-proxy-middleware.
We should place proxy middleware before parser middleware or you can try it out.
onProxyReq: function (proxyReq, req, res) {
if (req.body) {
const body = JSON.stringify(req.body)
proxyReq.setHeader('Content-Type', 'application/json')
proxyReq.setHeader('content-length', body.length)
delete req.body
proxyReq.write(body)
proxyReq.end()
}
},
Note: Changes has to be done with respect to content type