Add Postgres notify trigger for route updates

This adds triggers that send Postgres notifications for route_changes
when rows are inserted, updated and deleted for content items and
publish intents.

db/migrate/20241105135438_add_notify_trigger_for_route_changes.rb

@@ -0,0 +1,38 @@
+class AddNotifyTriggerForRouteChanges < ActiveRecord::Migration[7.2]
+  def up
+    execute <<-SQL
+      CREATE OR REPLACE FUNCTION notify_route_change() RETURNS trigger AS $$
+      BEGIN
+        PERFORM pg_notify('route_changes', '');
+        RETURN OLD;
+      END;
+      $$ LANGUAGE plpgsql;
+    SQL
+
+    execute <<-SQL
+      CREATE TRIGGER content_item_change_trigger
+      AFTER INSERT OR UPDATE OR DELETE ON content_items
+      FOR EACH ROW EXECUTE PROCEDURE notify_route_change();
+    SQL
+
+    execute <<-SQL
+      CREATE TRIGGER publish_intent_change_trigger
+      AFTER INSERT OR UPDATE OR DELETE ON publish_intents
+      FOR EACH ROW EXECUTE PROCEDURE notify_route_change();
+    SQL
+  end
+
+  def down
+    execute <<-SQL
+      DROP TRIGGER IF EXISTS content_item_change_trigger ON content_items;
+    SQL
+
+    execute <<-SQL
+      DROP TRIGGER IF EXISTS publish_intent_change_trigger ON publish_intents;
+    SQL
+
+    execute <<-SQL
+      DROP FUNCTION IF EXISTS notify_route_change();
+    SQL
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2024_03_12_132747) do
+ActiveRecord::Schema[7.2].define(version: 2024_11_05_135438) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -114,5 +114,4 @@
     t.index ["uid"], name: "index_users_on_uid", unique: true
     t.index ["updated_at"], name: "index_users_on_updated_at"
   end
-
 end

spec/integration/notify_route_change_spec.rb

@@ -0,0 +1,77 @@
+require "rails_helper"
+
+def postgres_listener(channel)
+  queue = Queue.new
+
+  Thread.new do
+    conn = ActiveRecord::Base.lease_connection
+    conn.execute("LISTEN #{channel}")
+    loop do
+      conn.raw_connection.wait_for_notify do |event, _id, _data|
+        queue << event
+      end
+    end
+  ensure
+    conn.execute "UNLISTEN #{channel}"
+  end
+
+  # Wait for the thread to be ready to listen for nofitications
+  sleep 0.1
+
+  queue
+end
+
+describe "Postgres trigger", type: :request, skip_db_cleaner: true do
+  before do
+    # We need to use truncation instead of transaction to ensure the changes are commited and the trigger is fired
+    DatabaseCleaner.clean
+    DatabaseCleaner.strategy = :truncation
+  end
+
+  it "sends a notification when content item created" do
+    listener = postgres_listener("route_changes")
+    create(:content_item)
+
+    expect(listener.pop).to eq("route_changes")
+  end
+
+  it "sends a notification when content item updated" do
+    content_item = create(:content_item)
+
+    listener = postgres_listener("route_changes")
+    content_item.update!(base_path: "/foo")
+
+    expect(listener.pop).to eq("route_changes")
+  end
+
+  it "sends a notification when content item destroyed" do
+    content_item = create(:content_item)
+    listener = postgres_listener("route_changes")
+    content_item.destroy!
+
+    expect(listener.pop).to eq("route_changes")
+  end
+
+  it "sends a notification when publish intent created" do
+    listener = postgres_listener("route_changes")
+    create(:publish_intent)
+
+    expect(listener.pop).to eq("route_changes")
+  end
+
+  it "sends a notification when publish intent updated" do
+    publish_intent = create(:publish_intent)
+    listener = postgres_listener("route_changes")
+    publish_intent.update!(publish_time: 10.minutes.from_now)
+
+    expect(listener.pop).to eq("route_changes")
+  end
+
+  it "sends a notification when publish intent destroyed" do
+    publish_intent = create(:publish_intent)
+    listener = postgres_listener("route_changes")
+    publish_intent.destroy!
+
+    expect(listener.pop).to eq("route_changes")
+  end
+end