8.1. Web site components¶
- A front-end web server such as Apache runs on your server and talks to the world. It serves static files and may run other web sites, but it routes a subset of its traffic to an internal TCP/IP port, where it finds CRATE.
- CRATE runs and serves content to an internal TCP/IP port.
- CRATE talks to one or more databases (e.g. MySQL, SQL Server). These include research databases, but also a database used by CRATE to store its own data.
- A separate CRATE subsystem handles back-end tasks, like sending e-mails
and processing consent requests (which can be a bit slow).
- This uses the Celery task queue system. Celery itself is a Python program that talks to a message queue, and can put messages into this queue (CRATE calls Celery) , or retrieve them from the queue (Celery calls CRATE)  to get jobs done.
- The actual message queue is managed by a “message broker”, which is software that provides message queues via AMQP; typically this broker is RabbitMQ.
- You can use Flower to monitor this system (see crate_launch_flower).
- Some sort of operating system supervisor typically controls the various aspects of CRATE. Under Windows, CRATE provides a Windows service (see CRATE Windows service). Under Linux, supervisor is typically used.
|||Gunicorn runs under Windows only|
|||In the source code, look for calls like