使用Laravel处理预订系统中的并发

Question

I'm developing a REST api in Laravel 5.2 with postgresql that handles bookings for diferent establishments that have an start_time and an end_time. The user can see in the frontend the diferents times available in a certain establishments and make a booking. Here is the problematic situation:

1. Customer A wants to book an establishment. Sees that the establishment A is free from 15:00 hs to 20:00 hs
2. Customer A selects the 16:00 to 17:00 time. (Have to press a button to confirm the booking)
3. Customer B wants to book an establishment. Sees that the establishment A is free from 15:00 hs to 20:00
4. Customer B selects the 16:00 to 17:00 apointment (Again, have to press a button to confirm the booking)
5. Customer A confirms the booking
6. If customer B confirms the booking, we will have 2 bookings at the same time.

Have read a lot about queues in laravel and I'm not really sure if that is the correct way to solve this problem.

The establishments doesnt have arbitrary hours so the customers can pick up a 1 or 2 or 3 hours booking.

This is my booking model

    Schema::create('bookings', function (Blueprint $table) {
        $table->increments('id');
        $table->timestamps();
        $table->timestamp('start_time');
        $table->timestamp('end_time');
        $table->integer('user_id')->nullable();
        $table->integer('establishment_id')->nullable();
        $table->string('name')->nullable();
        $table->string('phone_number')->nullable();

    });

Answer 1

Comments point to the fact that atomic data changes should be managed by the database. There are a few tools to help with this in most modern relational databases, eg transactions, foreign keys, composite keys and constraints. Eloquent and the query builder both have some support for all the above.

Using transactions you can lock a database table or tables whilst you read/write data. In the event of a failure all changes can be rolled back. This means you can carry out multiple dependent operations/changes with a guarantee that they will fail/succeed together and that external data changes cannot occur during that transaction.

Because you are not restricted to single hour bookings a simple composite key will not work but you can use transactions to query if a slot is available and then book the slot within the same transaction. This will be compatible with multiple rdb implementations via laravel / qb.

Another, possibly more performant approach would be to use composite keys with unique constraint and just book multiple 1 hour slots behind the scenes - this would restrict booking times to multiples of whatever booking unit you use, eg 1 hour units would not allow for a 1 1/2 hour booking, you would need 30 minute units

laravel transactions

laravel create composite indexes