Race condition when generating CustomFieldBehavior files

[mattgrayisok]

Description

If multiple simultaneous requests are received by Craft after compiled classes are cleared it's possible to hit a race condition when generating CustomFieldBehavior files. Resulting in:

2021-01-11 18:02:57 [-][-][-][error][yii\base\ErrorException:2] yii\base\ErrorException: rename(/var/www/html/storage/runtime/compiled_classes/CustomFieldBehavior_kcrkgabnyotw5ffc92d1058d85.79986753.php,/var/www/html/storage/runtime/compiled_classes/CustomFieldBehavior_kcrkgabnyotw.php): No such file or directory in /var/www/html/vendor/craftcms/cms/src/Craft.php:277

Stack trace:
#0 /var/www/html/vendor/craftcms/cms/src/web/ErrorHandler.php(76): yii\base\ErrorHandler->handleError(2, 'rename(/var/www...', '/var/www/html/v...', 277)
#1 [internal function]: craft\web\ErrorHandler->handleError(2, 'rename(/var/www...', '/var/www/html/v...', 277, Array)
#2 /var/www/html/vendor/craftcms/cms/src/Craft.php(277): rename('/var/www/html/s...', '/var/www/html/s...')
#3 /var/www/html/vendor/craftcms/cms/src/Craft.php(221): Craft::_generateCustomFieldBehavior(Array, '/var/www/html/s...', true, false)
#4 /var/www/html/vendor/craftcms/cms/src/Craft.php(169): Craft::_autoloadCustomFieldBehavior()

The offending code is here:

cms/src/Craft.php

Line 275 in cefde5c

$tmpFile = $dir . DIRECTORY_SEPARATOR . uniqid(pathinfo($filePath, PATHINFO_FILENAME), true) . '.php';

The problem exists because the temporary files being generated are prefixed with the same filename pattern that is used to clean up any old files. This causes the first request which exits the writeToFile mutex lock to delete the temp files created by any other simultaneously processing requests, subsequently causing them to error out on the following rename().

🥩

Steps to reproduce

1. Clear the compiled classes cache
2. Send some simultaneous requests to Craft

Additional info

• Craft version: 3.5
• PHP version: 7.4
• Database driver & version:
• Plugins & versions:

[brandonkelly]

Thanks for reporting that! Just fixed for the next release. Now Craft will only delete other CustomFieldBehavior classes that are over 10 seconds old.

[brandonkelly]

Craft 3.5.18 is out now with that fix ✨