Is using a reverse proxy considered best practice for a Phoenix setup?

Phoenix Forum Questions / Help
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There are use cases where a reverse proxy may be a necessity. There are administrators that are may be used to having a reverse proxy in place. More generally, however, do you consider the use of a reverse proxy to be best practice for a Phoenix setup?

Cowboy is great, for instance, but support for newer protocols (HTTP2, TLS 1.3) tends to lag considerably behind the likes of Nginx or Caddy. On the other hand, having fewer moving parts (here a lone Cowboy) is usually preferable. Other than the obvious “it depends”, what do you think?

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Caddy 2 supports http2 (but afaik you need tls setup for the upstream server):

Edit: Seems this has also been the case for caddy v1

3

I use nginx as reverse proxy now almost entirely because I found it much easier to use certbot/let’s encrypt with it. I also just know how to config nginx better than cowboy and it comes out of the box with most servers I’d be using, so it’s familiarity and convenience. Though yeah, I probably should consider trying a flow that uses just cowboy again some time.

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4

Just to bring some closure to this thread:

I decided to go down the reverse proxy path and tried Caddy. I got TLS 1.3 working in no time and removed much more configuration than I added! My basic setup required a Caddyfile as simple as this:

{
  http_port   [port1]
  https_port  [port2]
}

cdn.[my.website] www.[my.website] {
  reverse_proxy [ipv4]:[port3]
}

[my.website] {
  header strict-transport-security "max-age=63072000; includesubdomains; preload"
  redir https://www.[my.website]{uri}
}
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5

Having now spent some time experimenting with Caddy 2, I wish to share my experience as to how it complements my Phoenix setup, by compiling a list of areas in which Caddy excels:

• adding support for the latest protocols, such as TLS 1.3 or HTTP/3 (experimental)
• serving a maintenance page when the Cowboy / Phoenix web server is down
• adding security and other headers to all requests, or to a broad range of requests
• adding an authentication token header, e.g. to protect a staging server
• redirecting automatically from the domain root to the www subdomain
• dealing with the issue of trailing slashes in URL paths

On the contrary, I found that for complex request-specific operations (such as the addition of Content Security Policy headers), Caddy is not the right tool. Phoenix mechanisms offer far more flexibility.

I hope that someone finds this information useful.

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6

Given that three years have passed by, based on the experience what would the best approach on this topic? I am going through the same design decision for one of my project.

7

I am using Caddy, not only in production, but also in local. As it allows me to forget random port number to access different sub programs running alongside the server.

Plus I get HTTP/3, HTTPS and ease of configuration.

(common) {
	header /* {
		-server
		-X-Powered-By
		-via
	}
	@static {
		file
		path *.ico *.css *.js *.gif *.webp *.avif *.jpg *.jpeg *.png *.svg *.woff *.woff2
	}
	header @static cache-control "max-age=0; must-revalidate; public;"

	handle_errors {
		@custom_err file /errors/{err.status_code}.html /errors/error.html
		handle @custom_err {
			rewrite * {file_match.relative}
			file_server
		}
		respond "{err.status_code} {err.status_text}"
	}
}

www.derpytools.site {
	redir https://derpytools.site permanent
}

derpytools.site {
	tls certs/caddy/cert.pem certs/caddy/key.pem
	# tls /etc/caddy/certs/cert.pem /etc/caddy/certs/key.pem
	encode zstd gzip

	# Directly reverse proxy to Phoenix
	reverse_proxy localhost:4000

	# Proxy to Varnish Cache (Only use with production builds)
	# reverse_proxy localhost:3080

	import common
}

img.derpytools.site {
	# Directly reverse proxy to imgproxy
	reverse_proxy localhost:9080

	# Reverse proxy to Varnish cache instead (Only use with production builds)
	# reverse_proxy localhost:3080 {
	# 	# header_down Cache-Control "max-age=0; must-revalidate; public;"
	# 	# header_down Cache-Control "public; max-age=31536000; immutable;"
	# }

	import common
}

docs.derpytools.site {
	encode zstd gzip

	root * doc
	file_server browse
}

netdata.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:19999

	basicauth * {
		DerpyCoder $2b$05$4N/0p0i/fsNkiYHhNs9yruEMPbiOsQqxEfMkmrkan9w5hKNxSFRdK
	}

	import common
}

canary.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:4001

	basicauth * {
		DerpyCoder $2b$05$4N/0p0i/fsNkiYHhNs9yruEMPbiOsQqxEfMkmrkan9w5hKNxSFRdK
	}

	import common
}

metrics.derpytools.site {
	metrics

	import common
}

livebook.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:49223
}

search.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:7700
}

grafana.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:3000
}

prometheus.derpytools.site {
	encode zstd gzip

	reverse_proxy localhost:9090
}
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8

Having already detailed the usefulness of Caddy as a reverse proxy, it is also worth noting its web server capability. When Caddy runs on a separate host, static asset requests can be served locally, so that only dynamic asset requests need be forwarded to the Phoenix endpoint.

2 Likes
9

Thanks for coming back to me. I am leaning more towards Nginx as my reverse proxy, Looking to use the proxy server and also do the Authentication and Authorisation using Vouch Proxy.

The key question I am struggling with is - Should I use Phoenix to do the Authentication and Authorisation with Identity providers or use specific components like Vouch Proxy!!! Increases the moving parts in the deployment but has dedicated elements for specific functionality.

Any suggestions and advice is welcome.