How to set up http-proxy-middleware on a dynamic route? - node.js

Question

I'm trying to proxy some asset routes where a dynamic part of the path comes from a config file. I had this working using the request library, but I can't quite get it working with http-proxy-middleware.
Here's the code that works when I use the request library:
const assets = express.Router();
app.use(`/${p.name}/assets`, assets);
assets.get('*', async (req, res) => {
return request(`${p.address}/${p.version}/assets${req.path}`).pipe(res);
});
I've tried a few different variations with http-proxy-middleware, and none of these work. Example 1:
app.use(
`/${p.name}/assets`,
httpProxy({
target: `${p.address}`,
changeOrigin: true,
pathRewrite: {
[`^${p.name}`]: `${p.version}`,
},
})
);
Example 2:
app.use(
`/${p.name}/assets`,
httpProxy({
target: `${p.address}`,
changeOrigin: true,
pathRewrite: function(path) {
return path.replace(p.name, p.version);
}
})
);
I've also tried using /${p.name}/assets/** as the first argument to app.use, and I've also tried adding a /assets to the end of both the key and value in the pathRewrite object. The result is always the same: I get a 302 for the asset requested by the browser.
I've even tried adding a middleware function right before the httpProxy call that logs to the console so that I know my request is hitting the correct route:
app.use(
`/${p.name}/assets`,
(req, _res, next) => {
console.log("I'm an asset proxy, short and stout: ", req.url);
next();
},
httpProxy({
target: `${p.address}`,
changeOrigin: true,
pathRewrite: {
[`^${p.name}`]: `${p.version}`,
},
})
);
But I don't ever see that output. Probably a simple mistake. Perhaps my first argument to app.use just isn't right? Help appreciated!
Update
I also tried a combination of the old way and the new. I mounted a new router on /${p.name}/assets, and after discovering the onProxyRequest option, I added a function there to log some output.
const assets = express.Router();
app.use(`/${p.name}/assets`, assets);
assets.use(
'*',
httpProxy({
target: p.address,
changeOrigin: true,
pathRewrite: {
[`^${p.name}`]: p.version,
},
onProxyReq: (proxyReq, req, res) => {
console.log("Hello I'm being proxied now! ", proxyReq, req, res);
},
})
);
Still getting a 302, and I never see the output from the onProxyReq function.

Answer 1

Documentation has custom router option.
-
const proxyTable = {
'integration.localhost:3000': 'http://localhost:8001', // host only
'staging.localhost:3000': 'http://localhost:8002', // host only
'localhost:3000/api': 'http://localhost:8003', // host + path
'/rest': 'http://localhost:8004', // path only
};
const options = {
target: 'http://localhost:8000',
router: proxyTable,
};
const myProxy = createProxyMiddleware(options);
or
function customRouter(req) {
// I dont know what "p" stands for
// check the req object to see which property you want to modify
console.log(req)
const { hostname } = req
const hostName = hostname.split('.')[0]
return `https://${hostName}.sub.domain.com`
}
then add this option:
router: customRouter

Answer 2

Can you check your installed version - looks like you are using the v0.x.x.
interface to the http-proxy-middleware package. Latest is version 2.X.X and it exposes the following function
const { createProxyMiddleware } = require('http-proxy-middleware');
app.use(
`/${p.name}/assets`,
createProxyMiddleware({
target: `${p.address}`,
changeOrigin: true,
pathRewrite: {
[`^${p.name}`]: `${p.version}`,
},
})
);