MC-28948: Doesn't work: "Files" as fallback when Magento fails to connect to "Redis"

Author: ameysar

lib/internal/Magento/Framework/Session/SaveHandler.php

@@ -6,7 +6,7 @@
 namespace Magento\Framework\Session;
 
 use Magento\Framework\Session\Config\ConfigInterface;
-use \Magento\Framework\Exception\SessionException;
+use Magento\Framework\Exception\SessionException;
 
 /**
  * Magento session save handler
@@ -21,8 +21,21 @@ class SaveHandler implements SaveHandlerInterface
     protected $saveHandlerAdapter;
 
     /**
-     * Constructor
-     *
+     * @var SaveHandlerFactory
+     */
+    private $saveHandlerFactory;
+
+    /**
+     * @var ConfigInterface
+     */
+    private $sessionConfig;
+
+    /**
+     * @var string
+     */
+    private $defaultHandler;
+
+    /**
      * @param SaveHandlerFactory $saveHandlerFactory
      * @param ConfigInterface $sessionConfig
      * @param string $default
@@ -32,18 +45,22 @@ public function __construct(
         ConfigInterface $sessionConfig,
         $default = self::DEFAULT_HANDLER
     ) {
+        $this->saveHandlerFactory = $saveHandlerFactory;
+        $this->sessionConfig = $sessionConfig;
+        $this->defaultHandler = $default;
+
         /**
          * Session handler
          *
          * Save handler may be set to custom value in deployment config, which will override everything else.
          * Otherwise, try to read PHP settings for session.save_handler value. Otherwise, use 'files' as default.
          */
-        $saveMethod = $sessionConfig->getOption('session.save_handler') ?: $default;
+        $saveMethod = $this->sessionConfig->getOption('session.save_handler') ?: $this->defaultHandler;
 
         try {
-            $this->saveHandlerAdapter = $saveHandlerFactory->create($saveMethod);
+            $this->saveHandlerAdapter = $this->saveHandlerFactory->create($saveMethod);
         } catch (SessionException $e) {
-            $this->saveHandlerAdapter = $saveHandlerFactory->create($default);
+            $this->saveHandlerAdapter = $this->saveHandlerFactory->create($this->defaultHandler);
         }
     }
 
@@ -56,7 +73,7 @@ public function __construct(
      */
     public function open($savePath, $name)
     {
-        return $this->saveHandlerAdapter->open($savePath, $name);
+        return $this->callSafely('open', $savePath, $name);
     }
 
     /**
@@ -66,7 +83,7 @@ public function open($savePath, $name)
      */
     public function close()
     {
-        return $this->saveHandlerAdapter->close();
+        return $this->callSafely('close');
     }
 
     /**
@@ -77,7 +94,7 @@ public function close()
      */
     public function read($sessionId)
     {
-        return $this->saveHandlerAdapter->read($sessionId);
+        return $this->callSafely('read', $sessionId);
     }
 
     /**
@@ -89,7 +106,7 @@ public function read($sessionId)
      */
     public function write($sessionId, $data)
     {
-        return $this->saveHandlerAdapter->write($sessionId, $data);
+        return $this->callSafely('write', $sessionId, $data);
     }
 
     /**
@@ -100,19 +117,38 @@ public function write($sessionId, $data)
      */
     public function destroy($sessionId)
     {
-        return $this->saveHandlerAdapter->destroy($sessionId);
+        return $this->callSafely('destroy', $sessionId);
     }
 
     /**
-     * Garbage Collection - remove old session data older
-     * than $maxLifetime (in seconds)
+     * Garbage Collection - remove old session data older than $maxLifetime (in seconds)
      *
      * @param int $maxLifetime
      * @return bool
      * @SuppressWarnings(PHPMD.ShortMethodName)
      */
     public function gc($maxLifetime)
     {
-        return $this->saveHandlerAdapter->gc($maxLifetime);
+        return $this->callSafely('gc', $maxLifetime);
+    }
+
+    /**
+     * Call save handler adapter method.
+     *
+     * In case custom handler failed, default files handler is used.
+     *
+     * @param string $method
+     * @param mixed $arguments
+     *
+     * @return mixed
+     */
+    private function callSafely(string $method, ...$arguments)
+    {
+        try {
+            return $this->saveHandlerAdapter->{$method}(...$arguments);
+        } catch (SessionException $exception) {
+            $this->saveHandlerAdapter = $this->saveHandlerFactory->create($this->defaultHandler);
+            return $this->saveHandlerAdapter->{$method}(...$arguments);
+        }
     }
 }

lib/internal/Magento/Framework/Session/SaveHandler/Redis.php

@@ -43,14 +43,12 @@ class Redis implements \SessionHandlerInterface
      * @param ConfigInterface $config
      * @param LoggerInterface $logger
      * @param Filesystem $filesystem
-     * @throws SessionException
      */
     public function __construct(ConfigInterface $config, LoggerInterface $logger, Filesystem $filesystem)
     {
         $this->config = $config;
         $this->logger = $logger;
         $this->filesystem = $filesystem;
-        $this->getConnection();
     }
 
     /**