Issue #972528 by mkalkbrenner, harijari, ryanissamson, mikeytown2, haripalrao, kasperg: dblog fails to log MAX_ALLOWED_PACKET errors because they're longer than MAX_ALLOWED_PACKET

core/lib/Drupal/Core/Database/Driver/mysql/Connection.php

@@ -14,6 +14,7 @@ use Drupal\Core\Database\DatabaseNotFoundException;
 use Drupal\Core\Database\TransactionCommitFailedException;
 use Drupal\Core\Database\DatabaseException;
 use Drupal\Core\Database\Connection as DatabaseConnection;
+use Drupal\Component\Utility\Unicode;
 
 /**
  * @addtogroup database
@@ -34,6 +35,16 @@ class Connection extends DatabaseConnection {
    */
   protected $needsCleanup = FALSE;
 
+  /**
+   * The minimal possible value for the max_allowed_packet setting of MySQL.
+   *
+   * @link https://mariadb.com/kb/en/mariadb/server-system-variables/#max_allowed_packet
+   * @link https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_max_allowed_packet
+   *
+   * @var int
+   */
+  const MIN_MAX_ALLOWED_PACKET = 1024;
+
   /**
    * Constructs a Connection object.
    */
@@ -49,6 +60,24 @@ class Connection extends DatabaseConnection {
     $this->connectionOptions = $connection_options;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function query($query, array $args = array(), $options = array()) {
+    try {
+      return parent::query($query, $args, $options);
+    } catch (DatabaseException $e) {
+      if ($e->getPrevious()->errorInfo[1] == 1153) {
+        // If a max_allowed_packet error occurs the message length is truncated.
+        // This should prevent the error from recurring if the exception is
+        // logged to the database using dblog or the like.
+        $message = Unicode::truncateBytes($e->getMessage(), self::MIN_MAX_ALLOWED_PACKET);
+        $e = new DatabaseExceptionWrapper($message, $e->getCode(), $e->getPrevious());
+      }
+      throw $e;
+    }
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -278,6 +307,7 @@ class Connection extends DatabaseConnection {
       }
     }
   }
+
 }
 
 

core/modules/system/src/Tests/Database/LargeQueryTest.php

@@ -0,0 +1,58 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Database\LargeQueryTest.
+ */
+
+namespace Drupal\system\Tests\Database;
+
+use Drupal\Component\Utility\Environment;
+use Drupal\Core\Database\Database;
+use Drupal\Core\Database\DatabaseException;
+
+/**
+ * Tests handling of large queries.
+ *
+ * @group Database
+ */
+class LargeQueryTest extends DatabaseTestBase {
+
+  /**
+   * Tests truncation of messages when max_allowed_packet exception occurs.
+   */
+  function testMaxAllowedPacketQueryTruncating() {
+    // This test only makes sense if we are running on a MySQL database.
+    // Test if we are.
+    $database = Database::getConnectionInfo('default');
+    if ($database['default']['driver'] == 'mysql') {
+      // The max_allowed_packet value is configured per database instance.
+      // Retrieve the max_allowed_packet value from the current instance and
+      // check if PHP is configured with sufficient allowed memory to be able
+      // to generate a query larger than max_allowed_packet.
+      $max_allowed_packet = db_query('SELECT @@global.max_allowed_packet')->fetchField();
+      if (Environment::checkMemoryLimit($max_allowed_packet + (16 * 1024 * 1024))) {
+        $long_name = str_repeat('a', $max_allowed_packet + 1);
+        try {
+          db_query('SELECT name FROM {test} WHERE name = :name', array(':name' => $long_name));
+          $this->fail("An exception should be thrown for queries larger than 'max_allowed_packet'");
+        } catch (DatabaseException $e) {
+          // Close and re-open the connection. Otherwise we will run into error
+          // 2006 "MySQL server had gone away" afterwards.
+          Database::closeConnection();
+          Database::getConnection();
+          $this->assertEqual($e->getPrevious()->errorInfo[1], 1153, "Got a packet bigger than 'max_allowed_packet' bytes exception thrown.");
+          // Use strlen() to count the bytes exactly, not the unicode chars.
+          $this->assertTrue(strlen($e->getMessage()) <= $max_allowed_packet, "'max_allowed_packet' exception message truncated.");
+        }
+      }
+      else {
+        $this->verbose('The configured max_allowed_packet exceeds the php memory limit. Therefore the test is skipped.');
+      }
+    }
+    else {
+      $this->verbose('The test requires MySQL. Therefore the test is skipped.');
+    }
+  }
+
+}