Replacing nginx as a reverse-proxy with express - express

Question

I would like to replace nginx, serving as a reverse proxy, with an node js express application so I can set-up the rules dynamically and have better logging and testing possibilities.
My nginx set-up looks like:
http {
include mime.types;
default_type application/octet-stream;
sendfile off;
keepalive_timeout 65;
gzip on;
server {
listen 8023;
server_name localhost;
sendfile off;
location / {
proxy_pass https://main.app.url.com/;
}
location /module1/v1/ {
client_max_body_size 30000M;
client_body_buffer_size 200000k;
# local backend of module 1
proxy_pass http://localhost:8080/module1/v1/;
}
location /module1/v1/web/ {
# local front end files for module 1
alias /some/local/path/build/dist;
}
location /module2/v1/web/ {
# local front end files for module 1
alias /some/other/local/path/build/dist;
}
}
}
I tried to use the express-http-proxy middleware, but I am struggling with applying the above rules to it. First, I do not fully understand the difference between proxy_pass and alias directives.
Second I tried following:
const express = require('express');
const app = express();
const proxy = require('express-http-proxy')
const path = '/some/local/path/build/dist';
app.all('/module1/v1/web/', proxy(path, {
proxyReqPathResolver: (req) => {
return '';
}
})
);
};
I got an error:
TypeError: Cannot read property 'request' of undefined
at /Users/user1/Dev/local-dev-runner/node_modules/express-http-proxy/app/steps/sendProxyRequest.js:13:29
at new Promise (<anonymous>)
at sendProxyRequest (/Users/user1/Dev/local-dev-runner/node_modules/express-http-proxy/app/steps/sendProxyRequest.js:11:10)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:188:7)
Although cont path = 'http://www.google.com' returned an valid response.

Answer 1

So this is what I came with:
The trick is to serve local files and to proxy web requests. Apparently, nginx can automatically recognize whether the requests URI is an local or remote path.
I decided to use the nmp packages is-url and express-http-proxy so, the working solution looks like:
const express = require('express');
const app = express();
const isUrl = require('is-url');
const proxy = require('express-http-proxy');
...
/**
* Function adding new redirects to the current server instance. If the target URL is an URL the request will be
* handeled with the express-http-proxy middleware. If the target URL is some local directory the content will be serverd using the express-static middleware.
* #param matchedPath The path (endpoint) for which the redireciton should be configured.
* #param targetUrl The target URL or directory for the redirection.
*/
const setUpRedirect = (matchedPath, targetUrl, name) => {
// Use proxy for Urls
if (isUrl(targetUrl)) {
app.use(matchedPath,
proxy(targetUrl,
{
memoizeHost: false,
limit: '50mb',
proxyReqPathResolver: function(req) {
// I do not have (yet) any clue why I had to do this but it fixed the behavior
return req.originalUrl;
},
}),
)
}
else { // When targetUrl is directory serve static files from there
app.use(matchedPath,
express.static(targetUrl),
);
};
};
...
setUpRedirect('/module1/v1/web/:major([0-9]+).:minor([0-9]+).:bugfix([0-9]+)', '/some/local/path/build/dist';)
setUpRedirect('/module2/v1/web/:major([0-9]+).:minor([0-9]+).:bugfix([0-9]+)', 'http://some/remote/url/';)
server = app.listen(8080);