Chapter 10. Introducing Reactor
Have you ever held a subscription for a newspaper or a magazine? The internet has certainly taken a bite out of the subscriber base of traditional publications, but there was a time when a newspaper subscription was one of the best ways to keep up with the events of the day. You could count on a fresh delivery of current events every morning, to read during breakfast or on the way to work.
Now suppose that if, after paying for your subscription, several days go by and no papers have been delivered. A few more days go by, and you call the newspaper sales office to ask why you haven’t yet received your daily paper. Imagine your surprise if they explain, “You paid for a full year of newspapers. The year hasn’t completed yet. You’ll certainly receive them all once the full year of newspapers is ready.”
Thankfully, that’s not at all how subscriptions work. Newspapers have a certain timeliness to them. They’re delivered as quickly as possible after publication so that they can be read while their content is still fresh. Moreover, as you’re reading the latest issue, newspaper reporters are writing new stories for future editions, and the presses are fired up producing the next edition—all in parallel.
As we develop application code, there are two styles of code we can write: imperative and reactive: