Handling Concurrent User Registration with PHP and MySQL: Race Conditions
I've hit a wall trying to I'm working on a personal project and This might be a silly question, but I've been struggling with this for a few days now and could really use some help..... Building an application that allows users to register with unique usernames has led to a frustrating scenario. When two users try to register at the same time with the same username, I'm encountering race conditions that result in duplicate entries in the database. My current setup uses PHP 8.1 with MySQL for the backend. Here's a snippet of the registration code: ```php $username = $_POST['username']; $query = "INSERT INTO users (username) VALUES (:username)"; $stmt = $pdo->prepare($query); $stmt->execute(['username' => $username]); ``` The table is defined with a unique constraint on the `username` column. When the race condition occurs, one user gets inserted successfully, while the other receives a SQL error due to the unique constraint violation. The error I see is: ``` SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'username' for key 'username' ``` I've tried wrapping the insert in a transaction and implementing a retry mechanism for handling the exception, but this approach feels hacky and might still lead to a poor user experience. ```php try { $pdo->beginTransaction(); $stmt->execute(['username' => $username]); $pdo->commit(); } catch (PDOException $e) { $pdo->rollBack(); // Retry logic... } ``` Is there a more robust solution to handle this scenario? I'm also open to suggestions for alternative design patterns or best practices that could reduce the risk of race conditions in user registration workflows. How would you solve this? How would you solve this? My development environment is macOS. Any help would be greatly appreciated! My team is using Php for this microservice. Thanks in advance!