Fix PHP warnings when session backend exits before returning. (#3109)

Co-authored-by: Fabrizio Balliano <[email protected]>

Author: colinmollenhour

app/code/core/Mage/Core/Model/Session/Abstract/Varien.php

@@ -33,6 +33,7 @@ class Mage_Core_Model_Session_Abstract_Varien extends Varien_Object
     public const VALIDATOR_SESSION_LIFETIME            = 'session_lifetime';
     public const VALIDATOR_PASSWORD_CREATE_TIMESTAMP   = 'password_create_timestamp';
     public const SECURE_COOKIE_CHECK_KEY               = '_secure_cookie_check';
+    public const REGISTRY_CONCURRENCY_ERROR            = 'concurrent_connections_exceeded';
 
     /** @var bool Flag true if session validator data has already been evaluated */
     protected static $isValidated = false;
@@ -71,6 +72,9 @@ public function start($sessionName = null)
                 /* @var Cm_RedisSession_Model_Session $sessionResource */
                 $sessionResource = Mage::getSingleton('cm_redissession/session');
                 $sessionResource->setSaveHandler();
+                if (method_exists($sessionResource, 'setDieOnError')) {
+                    $sessionResource->setDieOnError(false);
+                }
                 break;
             case 'user':
                 // getSessionSavePath represents static function for custom session handler setup
@@ -148,7 +152,20 @@ public function start($sessionName = null)
             session_cache_limiter((string)$sessionCacheLimiter);
         }
 
-        session_start();
+        // Start session, abort and render error page if it fails
+        try {
+            if (session_start() === false) {
+                throw new Exception('Unable to start session.');
+            }
+        } catch (Throwable $e) {
+            session_abort();
+            if (Mage::registry(self::REGISTRY_CONCURRENCY_ERROR)) {
+                require_once Mage::getBaseDir() . DS . 'errors' . DS . '503.php';
+                die();
+            } else {
+                Mage::printException($e);
+            }
+        }
 
         Mage::dispatchEvent('session_before_renew_cookie', ['cookie' => $cookie]);
 

composer.json

@@ -23,7 +23,7 @@
         "ext-soap": "*",
         "ext-zlib": "*",
         "colinmollenhour/cache-backend-redis": "^1.14",
-        "colinmollenhour/magento-redis-session": "^3.0",
+        "colinmollenhour/magento-redis-session": "^3.1",
         "cweagans/composer-patches": "^1.7",
         "magento-hackathon/magento-composer-installer": "^3.1 || ^2.1 || ^4.0",
         "pelago/emogrifier": "^7.0",

composer.lock

@@ -61,5 +61,12 @@ services:
     volumes:
       - mysql:/var/lib/mysql
 
+  redis:
+    image: redis:6-alpine
+    command: redis-server --appendonly yes --maxmemory 10m
+    volumes:
+      - redis:/data
+
 volumes:
   mysql:
+  redis: