Move garbage collection into middleware

This prevents garbage collection to randomly break the installer:
before installation, the models that are being accessed have no
database connection.

Now, the middleware is only mounted into the forum's middleware
stack. I want API requests to have stable performance, and the
forum middleware stack is only mounted when Flarum is installed.

src/Forum/ForumServiceProvider.php

@@ -17,6 +17,7 @@ use Flarum\Extension\Event\Disabled;
 use Flarum\Extension\Event\Enabled;
 use Flarum\Foundation\AbstractServiceProvider;
 use Flarum\Http\Middleware\AuthenticateWithSession;
+use Flarum\Http\Middleware\CollectGarbage;
 use Flarum\Http\Middleware\DispatchRoute;
 use Flarum\Http\Middleware\HandleErrors;
 use Flarum\Http\Middleware\ParseJsonBody;
@@ -54,6 +55,7 @@ class ForumServiceProvider extends AbstractServiceProvider
             $pipe->pipe($app->make(HandleErrors::class, ['debug' => $debugMode]));
 
             $pipe->pipe($app->make(ParseJsonBody::class));
+            $pipe->pipe($app->make(CollectGarbage::class));
             $pipe->pipe($app->make(StartSession::class));
             $pipe->pipe($app->make(RememberFromCookie::class));
             $pipe->pipe($app->make(AuthenticateWithSession::class));

src/Http/Middleware/CollectGarbage.php

@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Http\Middleware;
+
+use Flarum\Http\AccessToken;
+use Flarum\User\AuthToken;
+use Flarum\User\EmailToken;
+use Flarum\User\PasswordToken;
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Zend\Stratigility\MiddlewareInterface;
+
+class CollectGarbage implements MiddlewareInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function __invoke(Request $request, Response $response, callable $out = null)
+    {
+        $this->collectGarbageSometimes();
+
+        return $out ? $out($request, $response) : $response;
+    }
+
+    private function collectGarbageSometimes()
+    {
+        // In order to save performance, we only execute this query
+        // from time to time (with 50% chance).
+        if (! $this->hit()) {
+            return;
+        }
+
+        AccessToken::whereRaw('last_activity <= ? - lifetime', [time()])->delete();
+
+        $earliestToKeep = date('Y-m-d H:i:s', time() - 24 * 60 * 60);
+
+        EmailToken::where('created_at', '<=', $earliestToKeep)->delete();
+        PasswordToken::where('created_at', '<=', $earliestToKeep)->delete();
+        AuthToken::where('created_at', '<=', $earliestToKeep)->delete();
+    }
+
+    private function hit()
+    {
+        return mt_rand(1, 100) <= 2;
+    }
+}

src/Http/Server.php

@@ -18,9 +18,6 @@ use Flarum\Http\Middleware\HandleErrors;
 use Flarum\Http\Middleware\StartSession;
 use Flarum\Install\InstallServiceProvider;
 use Flarum\Update\UpdateServiceProvider;
-use Flarum\User\AuthToken;
-use Flarum\User\EmailToken;
-use Flarum\User\PasswordToken;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Zend\Diactoros\Response\HtmlResponse;
@@ -67,9 +64,6 @@ class Server
      */
     public function __invoke(ServerRequestInterface $request, ResponseInterface $response, callable $out)
     {
-        // FIXME: Only call this when app is installed. Do this via middleware?
-        $this->collectGarbage();
-
         $middleware = $this->getMiddleware($request->getUri()->getPath());
 
         return $middleware($request, $response, $out);
@@ -152,24 +146,6 @@ class Server
         return $pipe;
     }
 
-    private function collectGarbage()
-    {
-        if ($this->hitsLottery()) {
-            AccessToken::whereRaw('last_activity <= ? - lifetime', [time()])->delete();
-
-            $earliestToKeep = date('Y-m-d H:i:s', time() - 24 * 60 * 60);
-
-            EmailToken::where('created_at', '<=', $earliestToKeep)->delete();
-            PasswordToken::where('created_at', '<=', $earliestToKeep)->delete();
-            AuthToken::where('created_at', '<=', $earliestToKeep)->delete();
-        }
-    }
-
-    private function hitsLottery()
-    {
-        return mt_rand(1, 100) <= 2;
-    }
-
     private function getErrorDir()
     {
         return __DIR__.'/../../error';