remedge / test_notification_service

Project setup

• setup .env.local file (copy from .env)
• composer install
• bin/console doctrine:database:create
• bin/console doctrine:migrations:migrate
• bin/console doctrine:fixtures:load

CRON Setup

• Add to crontab the command 0 0 * * * php /path/to/project/bin/console user:check-subscriptions-expiration.

Console Commands

• User creation: bin/console user:create {username} {email}.
• Checking subscriptions: bin/console user:check-subscriptions-expiration.
• Starting one consumer: php bin/console messenger:consume async -vv.

Project Description

• The project is implemented using the DDD approach.
• The entry points to the application are located in the App\User\Presentation\Cli folder.
• Stubs have been written for the functions check_email and send_email - App\User\Infrastructure\DummyEmailSender and App\User\Infrastructure\DummyEmailChecker.
• As there are more than 1 million emails and sending takes from 1 to 10 seconds, an asynchronous queue should be used for deferred sending, in this project symfony/doctrine-messenger is used.
• If possible, OOP should not be used - I hope this is a joke.

Data Description

• The User entity should always contain a valid email; if it's not valid, the entity should not be created in the database. The function check_email should be invoked when the User entity is created. An example of its use can be seen in the console command App\User\Presentation\Cli\CreateUserCommand.
• The validts field makes sense to bind to midnight, for example, "May 19 0:00" so that the CRON command can be run only once a day.
• The valid field is moved to a separate table called email_check_results, which represents cached verified emails, in order not to call the highly expensive check_email function.
• Indexes have been added to the fields confirmed and validts, as it's used for data selection.
• In the message {username}, your subscription is expiring soon it makes sense to mention exactly how many days are left until the subscription expires, which is done.

Load Calculation

Let's estimate the approximate number of necessary consumers for our queue. We have ~1,000,000 users. Sending 1 email takes from 1 to 10 seconds, we take the maximum - 10 seconds. Let's say we need to fit into 2 days with sending all the emails. 1,000,000 * 10 = 10,000,000 seconds = ~2777 hours = ~116 days. 116 / 2 = 58 consumers.