"Asymmetric transaction rollback error" in integration test

Question

I encountered this error in an integration test. It looks like on shutdown it tries to rollback a transaction which is not open.

Stack Trace

Fatal error: Uncaught Exception: Asymmetric transaction rollback. in .../vendor/magento/framework/DB/Adapter/Pdo/Mysql.php on line 272

Exception: Asymmetric transaction rollback. in .../vendor/magento/framework/DB/Adapter/Pdo/Mysql.php on line 272

Call Stack:
    1. {main}() .../vendor/phpunit/phpunit/phpunit:0
    2. PHPUnit_TextUI_Command::main() .../vendor/phpunit/phpunit/phpunit:47
    3. PHPUnit_TextUI_Command->run() .../vendor/phpunit/phpunit/src/TextUI/Command.php:110
    4. PHPUnit_TextUI_TestRunner->doRun() .../vendor/phpunit/phpunit/src/TextUI/Command.php:159
    5. PHPUnit_Framework_TestSuite->run() .../vendor/phpunit/phpunit/src/TextUI/TestRunner.php:440
    6. PHPUnit_Framework_TestSuite->run() .../vendor/phpunit/phpunit/src/Framework/TestSuite.php:747
    7. PHPUnit_Framework_TestSuite->run() .../vendor/phpunit/phpunit/src/Framework/TestSuite.php:747
    8. PHPUnit_Framework_TestCase->run() .../vendor/phpunit/phpunit/src/Framework/TestSuite.php:747
    9. PHPUnit_Framework_TestResult->run() .../vendor/phpunit/phpunit/src/Framework/TestCase.php:841
   10. PHPUnit_Framework_TestResult->endTest() .../vendor/phpunit/phpunit/src/Framework/TestResult.php:860
   11. Magento\TestFramework\Event\PhpUnit->endTest() .../vendor/phpunit/phpunit/src/Framework/TestResult.php:391
   12. Magento\TestFramework\EventManager->fireEvent() .../dev/tests/integration/framework/Magento/TestFramework/Event/PhpUnit.php:138
   13. call_user_func_array:{.../dev/tests/integration/framework/Magento/TestFramework/EventManager.php:49}() .../dev/tests/integration/framework/Magento/TestFramework/EventManager.php:49
   14. Magento\TestFramework\Event\Transaction->endTest() .../dev/tests/integration/framework/Magento/TestFramework/EventManager.php:49
   15. Magento\TestFramework\Event\Transaction->_processTransactionRequests() .../dev/tests/integration/framework/Magento/TestFramework/Event/Transaction.php:56
   16. Magento\TestFramework\Event\Transaction->_rollbackTransaction() .../dev/tests/integration/framework/Magento/TestFramework/Event/Transaction.php:78
   17. Magento\TestFramework\Db\Adapter\Mysql->rollbackTransparentTransaction() .../dev/tests/integration/framework/Magento/TestFramework/Event/Transaction.php:113
   18. Magento\Framework\DB\Adapter\Pdo\Mysql->rollBack() .../dev/tests/integration/framework/Magento/TestFramework/Db/Adapter/Mysql.php:51

It's hard to pinpoint the problem, so I cannot show relevant parts of the code under test, but I'll give some more background:

I did not use transactions on my own, but the test has a @magentoDataFixture where I create a product and a category and if I remove that, the error disappears.

The same fixture works in other tests.

I also use

 * @magentoAppIsolation enabled
 * @magentoDbIsolation enabled

but the same error occurs if I remove them.

What could possibly go wrong to lead to this error and how can I avoid this?

---

I added some logging to beginTransaction(), commit() and rollback() and found the following calls during test execution (calling class and "++", "--" on successful increment/decrement of transaction level):

array (
  0 => 'begin: Magento\\TestFramework\\Db\\Adapter\\Mysql',
  1 => '++',
  2 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  3 => '++',
  4 => 'begin: Magento\\Framework\\EntityManager\\Operation\\Update',
  5 => '++',
  6 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  7 => '++',
  8 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  9 => '++',
  10 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  11 => '--',
  12 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  13 => '--',
  14 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  15 => '++',
  16 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  17 => '--',
  18 => 'commit Magento\\Framework\\EntityManager\\Operation\\Update',
  19 => '--',
  20 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  21 => '--',
  22 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  23 => '++',
  24 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  25 => '--',
  26 => 'begin: Magento\\Catalog\\Model\\ResourceModel\\Product\\Indexer\\Eav\\AbstractEav',
  27 => '++',
  28 => 'commit Magento\\Catalog\\Model\\ResourceModel\\Product\\Indexer\\Eav\\AbstractEav',
  29 => '--',
  30 => 'begin: Magento\\Catalog\\Model\\ResourceModel\\Product\\Indexer\\Eav\\AbstractEav',
  31 => '++',
  32 => 'commit Magento\\Catalog\\Model\\ResourceModel\\Product\\Indexer\\Eav\\AbstractEav',
  33 => '--',
  34 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  35 => '++',
  36 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  37 => '--',
  38 => 'begin: Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  39 => '++',
  40 => 'commit Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  41 => '--',
  42 => 'rollback Magento\\Framework\\Model\\ResourceModel\\AbstractResource',
  43 => '--',
)

It looks like the last rollback comes out of nowhere, without matching begin, so that the next rollback from the test framework fails.

Answer 1

Found the culprit and it has nothing to do with the test framework: Magento\CatalogSearch\Model\Indexer\Fulltext\Plugin which adds commit callbacks for saving and deleting products.

If an exception is thrown in a commit callback, rollback() is called additionally to commit()

private function addCommitCallback(ResourceProduct $productResource, \Closure $proceed, AbstractModel $product)
{
    try {
        $productResource->beginTransaction();
        $result = $proceed($product);
        $productResource->addCommitCallback(function () use ($product) {
            $this->reindexRow($product->getEntityId());
        });
        $productResource->commit();
    } catch (\Exception $e) {
        $productResource->rollBack();
        throw $e;
    }

    return $result;
}

In Magento\Framework\Model\ResourceModel\AbstractResource, exceptions from the commit callbacks are simply rethrown:

public function commit()
{
    $this->getConnection()->commit();
    /**
     * Process after commit callbacks
     */
    if ($this->getConnection()->getTransactionLevel() === 0) {
        $callbacks = CallbackPool::get(spl_object_hash($this->getConnection()));
        try {
            foreach ($callbacks as $callback) {
                call_user_func($callback);
            }
        } catch (\Exception $e) {
            throw $e;
        }
    }
    return $this;
}

The two methods together lead to this nasty bug. To fix it, either exceptions from commit() or exceptions from the callbacks should probably be wrapped into a different exception type that can be handled differently by the core plugin.

I created an issue on GitHub: https://github.com/magento/magento2/issues/6497

Until this is fixed, "just" make sure that commit callbacks never throw exceptions...