createProxyMiddleware not working on Azure Webapp - express

Question

I'm running an Angular Universal application that is talking to an API. Now I'm trying to set up a proxy in the Universal server that proxies API requests to the actual API server:
server.use(['/api', '/sitemap.txt'], createProxyMiddleware({
target: process.env.API_URL,
onProxyReq: req => {
console.log('Using origin: ' + getOrigin(req.getHeaders()));
req.setHeader('origin', getOrigin(req.getHeaders()));
},
pathRewrite: {'^/api': ''}
}));
This works perfectly when running locally, but when running it on the server (Azure WebApp), it doesn't work. I can see the console log being called in the WebApp logs, but the resulting document is the Angular application with a message "page not found".
I'm totally out of ideas on where to look for solutions.
Edit:
I tried another proxy middleware and it does do the trick. This code works both locally and on Azure.
import * as proxy from 'express-http-proxy';
// ...
server.use(['/api', '/sitemap.txt'], proxy(process.env.API_URL, {
proxyPathResolver: req => {
let url: string = req.url;
if (url.startsWith('/api')) {
url = url.substr(4);
}
return url;
},
proxyReqOptDecorator(proxyReqOpts, srcReq) {
proxyReqOpts.headers['origin'] = getOrigin(proxyReqOpts.headers);
return proxyReqOpts;
}
}));
But it has some other limitations that make it unusable for our project, so I still need this resolved.

Answer 1

I have it working correctly now. This is the current setup:
server.use(
'/api',
createProxyMiddleware({
target: process.env.API_URL,
changeOrigin: true,
headers: {
Connection: 'keep-alive',
},
onProxyReq: (proxyReq, req, _res) => {
proxyReq.setHeader('origin', getOrigin(req.headers));
},
pathRewrite: {
'^/api': '',
},
})
);
So I added changeOrigin and the keep-alive header. I'm not sure which of the two resolved the issue, once I got it to work I never bothered to check it out. I suspect it's the header, though.