Report requests that PHP-FPM fails to start as errors

src/FpmRuntime/FpmHandler.php

@@ -187,6 +187,11 @@ public function handleRequest(HttpRequestEvent $event, Context $context): HttpRe
             throw new FastCgiCommunicationFailed;
         }
 
+        // PHP-FPM sends no output when it fails to start the request, such as running out of memory parsing the body
+        if ($response->getOutput() === '') {
+            throw new FastCgiCommunicationFailed('PHP-FPM failed to start the request, the PHP-FPM logs contain the error');
+        }
+
         $responseHeaders = $this->getResponseHeaders($response);
         // The status code is returned separately, it is not an HTTP header
         unset($responseHeaders['status']);

tests/FpmRuntime/FpmHandlerTest.php

@@ -3,6 +3,7 @@
 namespace Bref\Test\FpmRuntime;
 
 use Bref\Context\Context;
+use Bref\FpmRuntime\FastCgi\FastCgiCommunicationFailed;
 use Bref\FpmRuntime\FastCgi\Timeout;
 use Bref\FpmRuntime\FpmHandler;
 use Bref\Test\HttpRequestProxyTest;
@@ -1257,6 +1258,33 @@ public function test worker logs are still written in case of a timeou
         }
     }
 
+    public function test requests that FPM fails to start are reported as errors()
+    {
+        $this->fpm = new FpmHandler(__DIR__ . '/fixtures/request.php', __DIR__ . '/fixtures/php-fpm-low-memory.conf');
+        $this->fpm->start();
+
+        try {
+            $this->fpm->handle([
+                'version' => '1.0',
+                'httpMethod' => 'POST',
+                'headers' => [
+                    'Content-Type' => 'application/x-www-form-urlencoded',
+                ],
+                'body' => implode('&', array_map(fn (int $i) => "a{$i}[]=1", range(1, 50000))),
+            ], $this->fakeContext);
+            $this->fail('No exception was thrown');
+        } catch (FastCgiCommunicationFailed $e) {
+            self::assertSame('PHP-FPM failed to start the request, the PHP-FPM logs contain the error', $e->getMessage());
+
+            // PHP-FPM should work after that
+            $statusCode = $this->fpm->handle([
+                'version' => '1.0',
+                'httpMethod' => 'GET',
+            ], $this->fakeContext)['statusCode'];
+            self::assertEquals(200, $statusCode);
+        }
+    }
+
     /**
      * @see https://github.com/brefphp/bref/issues/316
      */

tests/FpmRuntime/fixtures/php-fpm-low-memory.conf

@@ -0,0 +1,10 @@
+error_log = /dev/null
+
+[default]
+pm = static
+pm.max_children = 1
+listen = /tmp/.bref/php-fpm.sock
+; Run out of memory parsing the test's request body, without displaying the error
+php_admin_value[memory_limit] = 8M
+php_admin_value[max_input_vars] = 100000
+php_admin_value[display_errors] = Off