Change Web Push API deliveries to use request pooling (#16014)

app/workers/web/push_notification_worker.rb

@@ -3,22 +3,67 @@
 class Web::PushNotificationWorker
   include Sidekiq::Worker
 
-  sidekiq_options backtrace: true, retry: 5
+  sidekiq_options queue: 'push', retry: 5
+
+  TTL     = 48.hours.to_s
+  URGENCY = 'normal'
 
   def perform(subscription_id, notification_id)
-    subscription = ::Web::PushSubscription.find(subscription_id)
-    notification = Notification.find(notification_id)
+    @subscription = Web::PushSubscription.find(subscription_id)
+    @notification = Notification.find(notification_id)
 
-    subscription.push(notification) unless notification.activity.nil?
-  rescue Webpush::ResponseError => e
-    code = e.response.code.to_i
+    # Polymorphically associated activity could have been deleted
+    # in the meantime, so we have to double-check before proceeding
+    return unless @notification.activity.present? && @subscription.pushable?(@notification)
 
-    if (400..499).cover?(code) && ![408, 429].include?(code)
-      subscription.destroy!
-    else
-      raise e
+    payload = @subscription.encrypt(push_notification_json)
+
+    request_pool.with(@subscription.audience) do |http_client|
+      request = Request.new(:post, @subscription.endpoint, body: payload.fetch(:ciphertext), http_client: http_client)
+
+      request.add_headers(
+        'Content-Type'     => 'application/octet-stream',
+        'Ttl'              => TTL,
+        'Urgency'          => URGENCY,
+        'Content-Encoding' => 'aesgcm',
+        'Encryption'       => "salt=#{Webpush.encode64(payload.fetch(:salt)).delete('=')}",
+        'Crypto-Key'       => "dh=#{Webpush.encode64(payload.fetch(:server_public_key)).delete('=')};#{@subscription.crypto_key_header}",
+        'Authorization'    => @subscription.authorization_header
+      )
+
+      request.perform do |response|
+        # If the server responds with an error in the 4xx range
+        # that isn't about rate-limiting or timeouts, we can
+        # assume that the subscription is invalid or expired
+        # and must be removed
+
+        if (400..499).cover?(response.code) && ![408, 429].include?(response.code)
+          @subscription.destroy!
+        elsif !(200...300).cover?(response.code)
+          raise Mastodon::UnexpectedResponseError, response
+        end
+      end
     end
   rescue ActiveRecord::RecordNotFound
     true
   end
+
+  private
+
+  def push_notification_json
+    json = I18n.with_locale(@subscription.locale || I18n.default_locale) do
+      ActiveModelSerializers::SerializableResource.new(
+        @notification,
+        serializer: Web::NotificationSerializer,
+        scope: @subscription,
+        scope_name: :current_push_subscription
+      ).as_json
+    end
+
+    Oj.dump(json)
+  end
+
+  def request_pool
+    RequestPool.current
+  end
 end