nginx reverse proxy to different applications based on an index in the host name - nginx

Question

Previously, I had a single staging environment reachable behind a DNS staging.example.com/. Behind this address is a nginx proxy with the following config. Note that my proxy either redirects
To a (s3 behind) cloudfront distribution (app1)
To a loadbalancer by forwarding the host name (and let's consider my ALB is able to pick the appropriate app based on the host name) (app2)
server {
listen 80;
listen 443 ssl;
server_name
staging.example.com
;
location / {
try_files /maintenance.html #app1;
}
location ~ /(faq|about_us|terms|press|...) {
try_files /maintenance.html #app2;
}
[...] # Lots of similar config than redirects either to app1 or app2
# Application hosted on s3 + CloudFront
location #app1 {
proxy_set_header Host app1-staging.example.com;
proxy_pass http://d2c72vkj8qy1kv.cloudfront.net;
}
# Application hosted behind a load balancer
location #app2 {
proxy_set_header Host app2-staging.example.internal;
proxy_set_header X-ALB-Host $http_host;
proxy_pass https://staging.example.internal;
}
}
Now, my team needs a couple more staging environments. We are not yet ready to transition to docker deployments (the ultimate goal of being able to spawn a complete infra per branch that we need to test... is a bit overkill given our team size) and I'm trying to pull out some tricks instead so we can easily get a couple more staging environments using roughly the same nginx config.
Assume I have a created a few more DNS names with a index_i like staging1.example.com, staging2.example.com. So my nginx proxy will receive requests with a host header that looks like staging#{index_i}.example.com
What I'm thinking of doing :
For my s3 + Cloudfront app, I'm thinking of nesting my files under [bucket_id]/#{index_i}/[app1_files] (previously they were directly in the root folder [bucket_id]/[app1_files])
For my load balancer app, let's assume my load balancer knows where to dispatch https://staging#{iindex_i}.example.com requests.
I'm trying to pull something like this
# incoming host : staging{index_i}.example.com`
server {
listen 80;
listen 443 ssl;
server_name
staging.example.com
staging1.example.com
staging2.example.com # I can list them manually, but is it possible to have something like `staging*.example.com` ?
;
[...]
location #app1 {
proxy_set_header Host app1-staging$index_i.example.com; # Note the extra index_i here
proxy_pass http://d2c72vkj8qy1kv.cloudfront.net/$index_i; # Here proxy_passing to a subfolder named index_i
}
location #app2 {
proxy_set_header Host app2-staging$index_i.example.internal; # Note the extra index_i here
proxy_set_header X-ALB-Host $http_host;
proxy_pass http://staging$index_i.example.internal; # Here I am just forwarding the host header basically
}
So ultimately my questions are
- When my nginx server receives a connexion, can I extract the index_i variable from the request host header (using maybe some regex ?)
- If yes, how can effectively implement the app1 and app2 blocks with index_i ?

Answer 1

After looking at several other questions, I was able to come up with this config that works perfectly: it's possible to extract the said variable using a regex in the host name.
On the downside, for my static single page applications, to make it work with S3, I had to create one bucket per "staging index" (because of the way static hosting on S3 works with website hosting / a single index.html to be used on 404). This made it in turn impossible to work with a single Cloudfront distribution in front of my (previously single) s3.
Here is example of using a proxy with a create-react-app frontend and server-side rendering behind an ALB
server {
listen 80;
listen 443 ssl;
server_name ~^staging(?<staging_index>\d*).myjobglasses.com$
location #create-react-app-frontend {
proxy_pass http://staging$staging_index.example.com.s3-website.eu-central-1.amazonaws.com;
}
location #server-side-rendering-app {
# Now Amazon Application Load Balancer can redirect traffic based on ANY HTTP header
proxy_set_header EXAMPLE-APP old-frontend;
proxy_pass https://staging$staging_index.myjobglasses.com;
}