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Many services, one cloudflared


4 min read
Route many different local services through many different URLs, with only one cloudflared

I work on the Argo Tunnel team, and we make a program called cloudflared, which lets you securely expose your web service to the Internet while ensuring that all its traffic goes through Cloudflare.

Say you have some local service (a website, an API, a TCP server, etc), and you want to securely expose it to the internet using Argo Tunnel. First, you run cloudflared, which establishes some long-lived TCP connections to the Cloudflare edge. Then, when Cloudflare receives a request for your chosen hostname, it proxies the request through those connections to cloudflared, which in turn proxies the request to your local service. This means anyone accessing your service has to go through Cloudflare, and Cloudflare can do caching, rewrite parts of the page, block attackers, or build Zero Trust rules to control who can reach your application (e.g. users with a email). Previously, companies had to use VPNs or firewalls to achieve this, but Argo Tunnel aims to be more flexible, more secure, and more scalable than the alternatives.

Some of our larger customers have deployed hundreds of services with Argo Tunnel, but they’re consistently experiencing a pain point with these larger deployments. Each instance of cloudflared can only proxy a single service. This means if you want to put, say, 100 services on the internet, you’ll need 100 instances of cloudflared running on your server. This is inefficient (because you’re using 100x as many system resources) and, even worse, it’s a pain to manage 100 long-lived services!

Today, we’re thrilled to announce our most-requested feature: you can now expose unlimited services using one cloudflared. Any customer can start using this today, at no extra cost, using the Named Tunnels we released a few months ago.

Named Tunnels

Earlier this year, we announced Named Tunnels—tunnels with immutable IDs that you can run and stop as you please. You can route traffic into the tunnel by adding a DNS or Cloudflare Load Balancer record, and you can route traffic from the tunnel into your local services by running cloudflared.

You can create a tunnel by running $ cloudflared tunnel create my_tunnel_name. Once you’ve got a tunnel, you can use DNS records or Cloudflare Load Balancers to route traffic into the tunnel. Once traffic is routed into the tunnel, you can use our new ingress rules to map traffic to local services.

Map traffic with ingress rules

An ingress rule basically says “send traffic for this internet URL to this local service.” When you invoke cloudflared it’ll read these ingress rules from the configuration file. You write ingress rules under the ingress key of your config file, like this:

$ cat ~/cloudflared_config.yaml

tunnel: my_tunnel_name
credentials-file: .cloudflared/e0000000-e650-4190-0000-19c97abb503b.json
 # Rules map traffic from a hostname to a local service:
 - hostname:
   service: https://localhost:8000
 # Rules can match the request's path to a regular expression:
 - hostname:
   path: /images/*\.(jpg|png|gif)
   service: https://machine1.local:3000
 # Rules can match the request's hostname to a wildcard character:
 - hostname: "*"
   service: ssh://localhost:2222
 # You can map traffic to the built-in “Hello World” test server:
 - hostname:
   service: hello_world
 # This “catch-all” rule doesn’t have a hostname/path, so it matches everything
 - service: http_status:404

This example maps traffic to three different local services. But cloudflared can map traffic to more than just addresses: it can respond with a given HTTP status (as in the last rule) or with the built-in Hello World test server (as in the second-last rule). See the docs for a full list of supported services.

You can match traffic using the hostname, a path regex, or both. If you don’t use any filters, the ingress rule will match everything (so if you have DNS records from different zones routing into the tunnel, the rule will match all their URLs). Traffic is matched to rules from top to bottom, so in this example, the last rule will match anything that wasn’t matched by an earlier rule. We actually require the last rule to match everything; otherwise, cloudflared could receive a request and not know what to respond with.

Testing your rules

To make sure all your rules are valid, you can run

$ cat ~/cloudflared_config_invalid.yaml

 - hostname:
   service: https://localhost:8000

$ cloudflared tunnel ingress validate
Validating rules from /usr/local/etc/cloudflared/config.yml
Validation failed: The last ingress rule must match all URLs (i.e. it should not have a hostname or path filter)

This will check that all your ingress rules use valid regexes and map to valid services, and it’ll ensure that your last rule (and only your last rule) matches all traffic. To make sure your ingress rules do what you expect them to do, you can run

$ cloudflared tunnel ingress rule
Using rules from ~/cloudflared_config.yaml
Matched rule #2
        path: /images/*\.(jpg|png|gif)

This will check which rule matches the given URL, almost like a dry run for the ingress rules (no tunnels are run and no requests are actually sent). It’s helpful for making sure you’re routing the right URLs to the right services!

Per-rule configuration

Whenever cloudflared gets a request from the internet, it proxies that request to the matching local service on your origin. Different services might need different configurations for this request; for example, you might want to tweak the timeout or HTTP headers for a certain origin. You can set a default configuration for all your local services, and then override it for specific ones, e.g.

  # Set configuration for all services
    connectTimeout: 30s
 # This service inherits all the default (root-level) configuration
 - hostname:
   service: https://localhost:8000
 # This service overrides the default configuration
 - service: https://localhost:8001
     connectTimeout: 10s
     disableChunkedEncoding: true
 # Catch-all rule doesn’t actually use any of the config
 - service: http_status:404

For a full list of configuration options, check out the docs.

What’s next?

We really hope this makes Argo Tunnel an even easier way to deploy services onto the Internet. If you have any questions, file an issue on our GitHub. Happy developing!

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Adam Chalmers|@adam_chal

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