NodeJS behind AWS ELB redirecting http to https failed health check - node.js

Question

I configured the ELB to open up both 80 and 443, where 443 is configured with SSL. Both ELB ports points to the instances' 80 port. The ELB's heatlh check is using ping target HTTP:80/index.html. It used to work, until I recently decided to start redirecting http to https.
Now the following codes are on the server.js(the codes within // are my newly added codes):
//
app.use(function(req, res, next) {
if (config.env === 'prod' && req.get('X-Forwarded-Proto') !== 'https') {
console.log("redirecting")
console.log('https://' + req.get('Host') + req.url)
res.set('X-Forwarded-Proto', 'https');
res.redirect('https://' + req.get('Host') + req.url);
}
else
next();
});
//
app.use(express.static(path.join(__dirname, 'home')));
app.set('trust proxy'); // enable this to trust the proxy
app.listen(app.get('port'), function() {
console.log('Express server listening on port ' + app.get('port'));
});
app.get("/*", function(req, res, next) {
res.sendFile(path.join(__dirname, 'home/index.html'));
});
I supposed the above request will redirect all request to the elb server but with https protocol.
However the server start printing:
redirecting
https://10.x.x.xx/index.html
And then the ELB is failing as https://10.x.x.xx/inde.html is not available.
However the index.html's location right under the {domain}/.
I think the way I redirect may be wrong - but I have no idea how to fix it.

Answer 1

My solution was to check for the health API route prior to redirecting.
Set up Health check on AWS load balancer to /api/health
Add condition
if (config.env === 'prod' && req.get('X-Forwarded-Proto') !== 'https' && req.url !== '/api/health') {
// redirect
}

Answer 2

The load balancer health check requests won't have the x-forwarded-proto header, since they haven't been forwarded from a client, they are coming directly from the load balancer. You probably need to check if the header exists first, before doing the redirect.
Also I'm a bit confused about your SSL setup. Are you doing SSL termination at the Load Balancer, but also serving an SSL certificate at the EC2 server? You say "Both ELB ports points to the instances' 80 port", which means you aren't serving an SSL certificate on the EC2 server, so your health check URL should be http instead of https.
Also this line that you have right before the redirect accomplishes nothing at all:
res.set('X-Forwarded-Proto', 'https');