MainProxy

Route requests to other Phoenix Endpoints or Plugs with WebSocket support.

This library is useful for Gigalixir, Render, Heroku or other deployments where only one web port is exposed.

Installation

Add MainProxy to your list of dependencies in mix.exs.

Note: if you are running an umbrella project, adding MainProxy as a dependency at the root mix.exs won't work. Instead, either add it to one of your child apps or create a new child app solely for the proxy.

def deps do
  [
    {:main_proxy, "~> 0.1"},
  ]
end

Configure rules for routing requests by adding configuration (i.e. config/config.exs). Backend configuration is optional and can be replaced by the merge_config/2 callback of your proxy module (more info below) if you need to generate configuration at runtime.

config :main_proxy,
  # any Cowboy options are allowed
  http: [:inet6, port: 4080],
  https: [:inet6, port: 4443]

Note: backends can also be configured via configuration, but configuring the backends via your proxy module (see the use MainProxy.Proxy example below) is recommended.

See Configuration Examples for more.

Then create the proxy module and add it to your application startup (often in MyApp.Application):

module:

defmodule MyApp.Proxy do
  use MainProxy.Proxy

  @impl MainProxy.Proxy
  def backends do
    [
      %{
        domain: "my-cool-app.com",
        phoenix_endpoint: MyCoolAppWeb.Endpoint
      },
      %{
        domain: "members.my-cool-app.com",
        phoenix_endpoint: MyAppMembersWeb.Endpoint
      },
      %{
        verb: ~r/get/i,
        path: ~r{^/main-proxy-plug-test$},
        plug: MainProxy.Plug.Test,
        opts: [1, 2, 3]
      }
    ]
  end
end

Proxies must be explicitly started as part of your application supervision tree. Proxies can be added to the supervision tree as follows (usually in MyApp.Application):

children = [
  # ... other children
  MyApp.Proxy,
]

To avoid the platform routing requests directly to your Web apps' Endpoints, and thus bypassing the Endpoint on which MainProxy is running, you can configure your other Web apps' Endpoints to not start a server in your production config.

# An Endpoint on which MainProxy is not running
config :my_app_web, MyAppWeb.Endpoint,
  # ...
  server: false

Available Options

• :http - the configuration for the HTTP server. It accepts all options as defined by Plug.Cowboy.
• :https - the configuration for the HTTPS server. It accepts all options as defined by Plug.Cowboy.
• :server - true by default. If you are running application with mix phx.server, this option is ignored, and the server will always be started.
• :backends - the rule for routing requests. See Configuration Examples for more.
  • :domain
  • :verb
  • :host
  • :path
  • :phoenix_endpoint / :plug
  • :opts - only for :plug
• :log_requests - true by default. Log the requests or not.

Configuration Examples

Route requests to apps based on hostname

defmodule MyApp.Proxy do
  use MainProxy.Proxy

  @impl MainProxy.Proxy
  def backends do
    [
      %{
        host: ~r{^app-name\.gigalixirapp\.com$},
        phoenix_endpoint: MyAppWeb.Endpoint
      },
      %{
        host: ~r{^www\.example\.com$},
        phoenix_endpoint: MyAppWeb.Endpoint
      },
      %{
        host: ~r{^api\.example\.com$},
        phoenix_endpoint: MyAppApiWeb.Endpoint
      },
      %{
        host: ~r{^members\.example\.com$},
        phoenix_endpoint: MyAppMembersWeb.Endpoint
      }
    ]
  end
end

Configuration via application config

config :main_proxy,
  http: [port: 80],
  backends: [
    %{
      host: ~r{^app-name\.gigalixirapp\.com$},
      phoenix_endpoint: MyAppWeb.Endpoint
    },
    %{
      host: ~r{^www\.example\.com$},
      phoenix_endpoint: MyAppWeb.Endpoint
    }
  ]

How does MainProxy work?

1. We start a Cowboy server with a single dispatch handler: MainProxy.Cowboy2Handler.
2. The handler checks the verb, host and path of the request, and compares them to the supplied configuration to determine where to route the request.
3. If the backend that matched is a phoenix_endpoint, MainProxy delegates to the Phoenix.Endpoint.Cowboy2Handler with your app's Endpoint.
4. If the backend that matched is a plug, MainProxy calls the plug as normal.
5. If no backend is matched, a text response with a status code of 404 is returned.

Development

mix run --no-halt
curl -i foo.com.127.0.0.1.xip.io:4080
curl -i localhost:4080

Thanks

This application is based on the main_proxy application inside the acme_bank project, which was based on a gist shared by Gazler.