fix: crash recovery (#729)

dev.exs

@@ -1220,8 +1220,8 @@ Task.start(fn ->
   children = [
     Demo.Repo,
     {Phoenix.PubSub, [name: Demo.PubSub]},
-    DemoWeb.Endpoint,
-    {Beacon, sites: [dev_site, dy_site]}
+    {Beacon, sites: [dev_site, dy_site]},
+    DemoWeb.Endpoint
   ]
 
   {:ok, _} = Supervisor.start_link(children, strategy: :one_for_one)

guides/general/troubleshooting.md

@@ -41,8 +41,3 @@ Note that if you're using `:host` on the scope and running in `localhost`,
 consider adding `"localhost"` to the list of allowed hosts.
 
 Also check the [Beacon.Router](https://hexdocs.pm/beacon/Beacon.Router.html) for more information.
-
-## RuntimeError - could not find persistent term for endpoint
-
-`Beacon` should be started after your host's `Endpoint`, please review the application children
-and make sure is declared after the endpoint.

guides/upgrading/v0.4.0.md

@@ -0,0 +1,19 @@
+# Upgrading to v0.4.0
+
+## Move `Beacon` before the endpoint in application.ex
+
+Open the file `application.ex`, find the Beacon tuple in the list of `children`,
+and move it to before the endpoint(s) declarations:
+
+```elixir
+@impl true
+def start(_type, _args) do
+  children = [
+    # ...
+    {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site)]]}, # <- moved to before `MyAppWeb.Endpoint`
+    MyAppWeb.Endpoint
+  ]
+```
+
+In v0.3.0 the order was inverted which caused a regression on crash recoveries.
+

lib/beacon/beacon.ex

@@ -58,13 +58,12 @@ defmodule Beacon do
         children = [
           MyApp.Repo,
           {Phoenix.PubSub, name: MyApp.PubSub},
-          MyAppWeb.Endpoint,
-          {Beacon,
-           [
-             sites: [
-               Application.fetch_env!(:beacon, :my_site)
-             ]
-           ]}
+          {Beacon, [
+            sites: [
+              Application.fetch_env!(:beacon, :my_site)
+            ]
+          ]},
+          MyAppWeb.Endpoint
         ]
 
         opts = [strategy: :one_for_one, name: MyApp.Supervisor]

lib/beacon/private.ex

@@ -6,6 +6,15 @@ defmodule Beacon.Private do
 
   # Should be avoided as much as possible.
 
+  @doc """
+  Fetch the host app `:otp_app` from the Repo config.
+  """
+  def otp_app!(%Beacon.Config{repo: repo}) do
+    repo.config()[:otp_app] || raise Beacon.RuntimeError, "failed to discover :otp_app"
+  rescue
+    _ -> reraise Beacon.RuntimeError, [message: "failed to discover :otp_app, make sure Repo is started before Beacon"], __STACKTRACE__
+  end
+
   @phoenix_live_view_version to_string(Application.spec(:phoenix_live_view)[:vsn])
 
   @doc """
@@ -48,4 +57,17 @@ defmodule Beacon.Private do
       Phoenix.LiveView.Route.live_link_info(endpoint, router, url)
     end
   end
+
+  def endpoint_config(otp_app, endpoint) do
+    Phoenix.Endpoint.Supervisor.config(otp_app, endpoint)
+  end
+
+  def endpoint_host(otp_app, endpoint) do
+    url_config = endpoint_config(otp_app, endpoint)[:url]
+    host_to_binary(url_config[:host] || "localhost")
+  end
+
+  # https://github.com/phoenixframework/phoenix/blob/4ebefb9d1f710c576f08c517f5852498dd9b935c/lib/phoenix/endpoint/supervisor.ex#L301-L302
+  defp host_to_binary({:system, env_var}), do: host_to_binary(System.get_env(env_var))
+  defp host_to_binary(host), do: host
 end

lib/beacon/router.ex

@@ -257,15 +257,16 @@ defmodule Beacon.Router do
   #
   # It's considered reachable if a dynamic page can be served on the site prefix.
   def reachable?(%Beacon.Config{} = config, opts \\ []) do
+    otp_app = Beacon.Private.otp_app!(config)
     %{site: site, endpoint: endpoint, router: router} = config
-    reachable?(site, endpoint, router, opts)
+    reachable?(site, endpoint, router, otp_app, opts)
   rescue
     # missing router or missing beacon macros in the router
     _ -> false
   end
 
-  defp reachable?(site, endpoint, router, opts) do
-    host = Keyword.get_lazy(opts, :host, fn -> endpoint.host() end)
+  defp reachable?(site, endpoint, router, otp_app, opts) do
+    host = Keyword.get_lazy(opts, :host, fn -> Beacon.Private.endpoint_host(otp_app, endpoint) end)
 
     prefix =
       Keyword.get_lazy(opts, :prefix, fn ->

lib/mix/tasks/beacon.gen.site.ex

@@ -188,7 +188,8 @@ defmodule Mix.Tasks.Beacon.Gen.Site do
         quote do
           [sites: [Application.fetch_env!(:beacon, unquote(site))]]
         end}},
-      after: [repo, endpoint],
+      after: [repo],
+      before: [endpoint],
       opts_updater: fn zipper ->
         with {:ok, zipper} <-
                Igniter.Code.Keyword.put_in_keyword(

test/mix/tasks/gen_site_test.exs

@@ -137,8 +137,13 @@ defmodule Mix.Tasks.Beacon.GenSiteTest do
       project
       |> Igniter.compose_task("beacon.gen.site", @opts_my_site)
       |> assert_has_patch("lib/test/application.ex", """
-      20 + |      TestWeb.Endpoint,
-      21 + |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site)]]}
+            ...|
+       12 12   |      Test.Repo,
+       13 13   |      {DNSCluster, query: Application.get_env(:test, :dns_cluster_query) || :ignore},
+          14 + |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site)]]},
+       14 15   |      {Phoenix.PubSub, name: Test.PubSub},
+       15 16   |      # Start the Finch HTTP client for sending emails
+            ...|
       """)
     end
 
@@ -148,8 +153,8 @@ defmodule Mix.Tasks.Beacon.GenSiteTest do
       |> apply_igniter!()
       |> Igniter.compose_task("beacon.gen.site", @opts_other_site)
       |> assert_has_patch("lib/test/application.ex", """
-      21    - |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site)]]}
-         21 + |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site), Application.fetch_env!(:beacon, :other)]]}
+      14    - |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site)]]},
+         14 + |      {Beacon, [sites: [Application.fetch_env!(:beacon, :my_site), Application.fetch_env!(:beacon, :other)]]},
       """)
     end
   end