Created middleware which closes DB connection after every request

config/autoload/entity-manager.global.php

@@ -1,7 +1,7 @@
 <?php
 declare(strict_types=1);
 
-use Shlinkio\Shlink\Common;
+use function Shlinkio\Shlink\Common\env;
 
 return [
 
@@ -10,9 +10,9 @@ return [
             'proxies_dir' => 'data/proxies',
         ],
         'connection' => [
-            'user' => Common\env('DB_USER'),
-            'password' => Common\env('DB_PASSWORD'),
-            'dbname' => Common\env('DB_NAME', 'shlink'),
+            'user' => env('DB_USER'),
+            'password' => env('DB_PASSWORD'),
+            'dbname' => env('DB_NAME', 'shlink'),
             'charset' => 'utf8',
         ],
     ],

config/autoload/middleware-pipeline.global.php

@@ -10,10 +10,18 @@ return [
 
     'middleware_pipeline' => [
         'pre-routing' => [
-            'middleware' => [
+            'middleware' => (function () {
+                $middleware = [
                     ErrorHandler::class,
                     Expressive\Helper\ContentLengthMiddleware::class,
-            ],
+                ];
+
+                if (Common\Exec\ExecutionContext::currentContextIsSwoole()) {
+                    $middleware[] = Common\Middleware\CloseDbConnectionMiddleware::class;
+                }
+
+                return $middleware;
+            })(),
             'priority' => 12,
         ],
         'pre-routing-rest' => [

module/Common/config/dependencies.config.php

@@ -31,6 +31,7 @@ return [
             Template\Extension\TranslatorExtension::class => ConfigAbstractFactory::class,
 
             Middleware\LocaleMiddleware::class => ConfigAbstractFactory::class,
+            Middleware\CloseDbConnectionMiddleware::class => ConfigAbstractFactory::class,
             IpAddress::class => Middleware\IpAddressMiddlewareFactory::class,
 
             Image\ImageBuilder::class => Image\ImageBuilderFactory::class,
@@ -78,6 +79,7 @@ return [
 
         Template\Extension\TranslatorExtension::class => ['translator'],
         Middleware\LocaleMiddleware::class => ['translator'],
+        Middleware\CloseDbConnectionMiddleware::class => ['em'],
 
         IpGeolocation\IpApiLocationResolver::class => ['httpClient'],
         IpGeolocation\GeoLite2LocationResolver::class => [Reader::class],

module/Common/src/Middleware/CloseDbConnectionMiddleware.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Common\Middleware;
+
+use Doctrine\ORM\EntityManagerInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+
+class CloseDbConnectionMiddleware implements MiddlewareInterface
+{
+    /** @var EntityManagerInterface */
+    private $em;
+
+    public function __construct(EntityManagerInterface $em)
+    {
+        $this->em = $em;
+    }
+
+    /**
+     * Process an incoming server request and return a response, optionally delegating
+     * response creation to a handler.
+     */
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $handledRequest =  $handler->handle($request);
+        $this->em->getConnection()->close();
+
+        return $handledRequest;
+    }
+}

module/Common/test/Middleware/CloseDbConnectionMiddlewareTest.php

@@ -0,0 +1,53 @@
+<?php
+declare(strict_types=1);
+
+namespace ShlinkioTest\Shlink\Common\Middleware;
+
+use Doctrine\DBAL\Connection;
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\Framework\TestCase;
+use Prophecy\Prophecy\ObjectProphecy;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Common\Middleware\CloseDbConnectionMiddleware;
+use Zend\Diactoros\Response;
+use Zend\Diactoros\ServerRequestFactory;
+
+class CloseDbConnectionMiddlewareTest extends TestCase
+{
+    /** @var CloseDbConnectionMiddleware */
+    private $middleware;
+    /** @var ObjectProphecy */
+    private $handler;
+    /** @var ObjectProphecy */
+    private $em;
+
+    public function setUp()
+    {
+        $this->handler = $this->prophesize(RequestHandlerInterface::class);
+        $this->em = $this->prophesize(EntityManagerInterface::class);
+
+        $this->middleware = new CloseDbConnectionMiddleware($this->em->reveal());
+    }
+
+    /**
+     * @test
+     */
+    public function connectionIsClosedWhenMiddlewareIsProcessed()
+    {
+        $req = ServerRequestFactory::fromGlobals();
+        $resp = new Response();
+
+        $conn = $this->prophesize(Connection::class);
+        $closeConn = $conn->close()->will(function () {
+        });
+        $getConn = $this->em->getConnection()->willReturn($conn->reveal());
+        $handle = $this->handler->handle($req)->willReturn($resp);
+
+        $result = $this->middleware->process($req, $this->handler->reveal());
+
+        $this->assertSame($result, $resp);
+        $getConn->shouldHaveBeenCalledOnce();
+        $closeConn->shouldHaveBeenCalledOnce();
+        $handle->shouldHaveBeenCalledOnce();
+    }
+}