Http-proxy-middleware with ExpressJS returns error while proxying to http://jsonplaceholder

Question

I am basically following the code in here.

I generate my Express project using npx express-generator

In my routes/index.js I do this

var express = require("express");
var router = express.Router();
const {
  createProxyMiddleware
} = require("http-proxy-middleware");

/**
 * Configure proxy middleware
 */
const jsonPlaceholderProxy = createProxyMiddleware({
  target: "http://jsonplaceholder.typicode.com/users",
  changeOrigin: true, // for vhosted sites, changes host header to match to target's host
  logger: console,
});

router.use('/test', jsonPlaceholderProxy);

module.exports = router;

In my app.js I just redirect all / request to my routes/index.js by doing this

var createError = require("http-errors");
var express = require("express");
var path = require("path");
var cookieParser = require("cookie-parser");
var logger = require("morgan");

var indexRouter = require("./routes/index");

var app = express();

// view engine setup
app.set("views", path.join(__dirname, "views"));
app.set("view engine", "ejs");

app.use(logger("dev"));
app.use(express.json());
app.use(express.urlencoded({
  extended: false
}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, "public")));

app.use("/", indexRouter);  

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// 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;

I start the app by running npm start

I can see

npm start

project@0.0.0 start
node ./bin/www  

[HPM] Proxy created: /  -> http://jsonplaceholder.typicode.com/users

So far so good. My app is running on http://localhost:3000

Now I use Postman to hit http://localhost:3000/test (GET)

I get http status code 504 Gateway Timeout with message [HPM] Error occurred while proxying request localhost:3000/test to http://jsonplaceholder.typicode.com/

Meanwhile, if I hit http://jsonplaceholder.typicode.com/users (GET) directly using Postman, I get status 200 and a very long JSON body as the response , indicating that the API is live and running OK.

I am wondering, what have I done wrongly?

---

Update with the solution

I fix the issue by

1. Adding pathRewrite as suggested by @Mahesh
2. Remove all the middlewares added automatically by express-generator

For this simple scenario, I don't need those middlewares. But definitely there are some scenarios that may need those middlewares. Not sure how to solve the issue when we do need those middlewares.

So, the routes/index.js looks like this

var express = require("express");
var router = express.Router();
const {
  createProxyMiddleware
} = require("http-proxy-middleware");

/**
 * Configure proxy middleware
 */
const jsonPlaceholderProxy = createProxyMiddleware({
  target: "http://jsonplaceholder.typicode.com/users/",
  changeOrigin: true, // for vhosted sites, changes host header to match to target's host
  logger: console,
  pathRewrite: {
    // Rewrite the request path to remove the `/test` prefix
    "^/test": "",
  },
});

router.use("/test", jsonPlaceholderProxy);

module.exports = router;

And my app.js looks like this

var createError = require("http-errors");
var express = require("express");
var path = require("path");
var cookieParser = require("cookie-parser");
var logger = require("morgan");
var bodyParser = require('body-parser')

var indexRouter = require("./routes/index");

var app = express();

// view engine setup
app.set("views", path.join(__dirname, "views"));
app.set("view engine", "ejs");


//Remove all these parsers added automatically by express-generator
//Activating these line below would make the proxy fails. Not sure why?
/*
app.use(logger("dev"));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, "public")));
app.use(bodyParser.json());
app.use(bodyParser.raw());
app.use(bodyParser.text());
*/

app.use("/", indexRouter);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// 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;

Re-run the app, and hit http://localhost:3000/test again using Postman. Now it works.

Answer 1

I think this will fix your issue

 const jsonPlaceholderProxy = createProxyMiddleware({
  target: "http://jsonplaceholder.typicode.com/users",
  changeOrigin: true, // for vhosted sites, changes host header to match to target's host
  logger: console,
  pathRewrite: {
    // Rewrite the request path to remove the `/test` prefix
    "^/test": "",
  },
})

The issue with the original code was that the /test prefix was included in the request path when the proxy middleware was used. This caused the requests to be sent to the wrong URL.