Does http-proxy-middleware work with Serverless Lambda? - http

Question

I'm trying to proxy an external API through Serverless Lambda. Trying the following example for the code below: http://localhost:3000/users/1 returns 200 but body is empty. I must be overlooking something as http://localhost:3000/users/11 returns a 404 (as expected).
index.js
'use strict';
const serverless = require('serverless-http');
const express = require('express');
const {
createProxyMiddleware
} = require('http-proxy-middleware');
const app = express();
const jsonPlaceholderProxy = createProxyMiddleware({
target: 'http://jsonplaceholder.typicode.com',
changeOrigin: true,
logLevel: 'debug'
});
app.use('/users', jsonPlaceholderProxy);
app.get('/', (req, res) => {
res.json({
msg: 'Hello from Serverless!'
})
})
const handler = serverless(app);
module.exports.handler = async (event, context) => {
try {
const result = await handler(event, context);
return result;
} catch (error) {
return error;
}
};
serverless.yml
service: sls-proxy-test
provider:
name: aws
runtime: nodejs12.x
plugins:
- serverless-offline
functions:
app:
handler: index.handler
events:
- http:
method: ANY
path: /
- http: "ANY {proxy+}"
package.json
{
"name": "proxy",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"sls": "sls",
"offline": "sls offline start"
},
"keywords": [],
"author": "",
"license": "ISC",
"dependencies": {
"express": "4.17.1",
"http-proxy-middleware": "1.0.1",
"serverless-http": "2.3.2"
},
"devDependencies": {
"serverless": "1.65.0",
"serverless-offline": "5.12.1"
}
}

Answer 1

try to remove the transfer-encoding header from the response in onProxyRes listener inside createProxyMiddleware
const jsonPlaceholderProxy = createProxyMiddleware({
onProxyRes: function (proxyRes, req, res) { // listener on response
delete proxyRes.headers['transfer-encoding']; // remove header from response
},
// remaining code

Answer 2

I had the same issue but adding the below onProxyRes option solved it
onProxyRes(proxyRes, req, res) {
const bodyChunks = [];
proxyRes.on('data', (chunk) => {
bodyChunks.push(chunk);
});
proxyRes.on('end', () => {
const body = Buffer.concat(bodyChunks);
res.status(proxyRes.statusCode);
Object.keys(proxyRes.headers).forEach((key) => {
res.append(key, proxyRes.headers[key]);
});
res.send(body);
res.end();
});
}