fix(portal): Properly check background jobs (#8986)

The `background_jobs_enabled` config in an ENV var that needs to be set
for a specific configuration key. It's not set on the top-level
`:domain` config by default.

Instead, it's used to enable / disable specific modules to start by the
application's Supervisor.

The `Domain.Events.ReplicationConnection` module is updated in this PR
to follow this convention.

elixir/apps/domain/lib/domain/application.ex

@@ -41,41 +41,9 @@ defmodule Domain.Application do
 
       # Observability
       Domain.Telemetry
-    ] ++ background_children()
-  end
-
-  defp background_children do
-    if background_jobs_enabled?() do
-      [
-        # Job system
-        {Oban, Application.fetch_env!(:domain, Oban)},
-
-        # WAL replication
-        replication_child_spec()
-      ]
-    else
-      []
-    end
-  end
-
-  defp replication_child_spec do
-    {connection_opts, config} =
-      Application.fetch_env!(:domain, Domain.Events.ReplicationConnection)
-      |> Keyword.pop(:connection_opts)
-
-    init_state = %{
-      connection_opts: connection_opts,
-      instance: struct(Domain.Events.ReplicationConnection, config)
-    }
-
-    %{
-      id: Domain.Events.ReplicationConnection,
-      start: {Domain.Events.ReplicationConnection, :start_link, [init_state]},
-      restart: :transient,
-      # Allow up to 240 restarts in 20 minutes - covers duration of a deploy
-      max_restarts: 240,
-      max_seconds: 1200
-    }
+    ] ++
+      oban() ++
+      replication()
   end
 
   defp configure_logger do
@@ -109,12 +77,40 @@ defmodule Domain.Application do
     end
   end
 
-  defp background_jobs_enabled? do
-    # The web and api applications also start Domain's supervision tree so that they may
-    # use the same database connection pool and other shared resources. We want to restrict
-    # some children to only run in the domain node.
-    # For now, we use BACKGROUND_JOBS_ENABLED to determine if we are running in the domain node.
-    # We could also use the node's name, but this doesn't work as well in dev/test environments.
-    Application.get_env(:domain, :background_jobs_enabled, false)
+  # TODO: Configure Oban workers to only run on domain nodes
+  defp oban do
+    [{Oban, Application.fetch_env!(:domain, Oban)}]
+  end
+
+  defp replication do
+    config = Application.fetch_env!(:domain, Domain.Events.ReplicationConnection)
+
+    if config[:enabled] do
+      [
+        replication_child_spec()
+      ]
+    else
+      []
+    end
+  end
+
+  defp replication_child_spec do
+    {connection_opts, config} =
+      Application.fetch_env!(:domain, Domain.Events.ReplicationConnection)
+      |> Keyword.pop(:connection_opts)
+
+    init_state = %{
+      connection_opts: connection_opts,
+      instance: struct(Domain.Events.ReplicationConnection, config)
+    }
+
+    %{
+      id: Domain.Events.ReplicationConnection,
+      start: {Domain.Events.ReplicationConnection, :start_link, [init_state]},
+      restart: :transient,
+      # Allow up to 240 restarts in 20 minutes - covers duration of a deploy
+      max_restarts: 240,
+      max_seconds: 1200
+    }
   end
 end

elixir/config/config.exs

@@ -31,6 +31,7 @@ config :domain, Domain.Repo,
   start_apps_before_migration: [:ssl, :logger_json]
 
 config :domain, Domain.Events.ReplicationConnection,
+  enabled: true,
   connection_opts: [
     hostname: "localhost",
     port: 5432,

elixir/config/runtime.exs

@@ -28,6 +28,7 @@ if config_env() == :prod do
            )
 
   config :domain, Domain.Events.ReplicationConnection,
+    enabled: compile_config!(:background_jobs_enabled),
     connection_opts: [
       hostname: compile_config!(:database_host),
       port: compile_config!(:database_port),