Let work enter at a pace the service can handle

Imagine a busy ticket desk with a shared address book. Learn what an admission rule protects, and what it cannot promise to visitors.

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Visitors share a limited resource

A request is a visitor asking the application, a program, to do a task. A database stores the information the program needs. Visitors may arrive faster than that database can serve them, just as a ticket desk can become busier than its staff can handle.

Words in this chapter

Request: An instruction sent to the service.
Application: The program carrying out the visitor's task.
Database: The store of information the application looks up.

THE IDEA TO KEEP

Serving a request uses resources behind the application.

Opening the illustration…

Parts and connections

A visitorWaiting

A person asking to use the service.

ApplicationWaiting

The program doing the visitor's task.

Shared databaseWaiting

The limited lookup resource behind the application.