Cloud Native Go, 2nd Edition

Chapter 6. Cloud Native Design Principles

The most important property of a program is whether it accomplishes the intention of its user.¹

C. A. R. Hoare, Communications of the ACM (October 1969)

Professor Sir Charles Antony Richard (Tony) Hoare is a brilliant guy. He invented quicksort, authored Hoare Logic for reasoning about the correctness of computer programs, and created the formal language “communicating sequential processes” (CSP) that inspired Go’s beloved concurrency model. Oh, and he developed the structured programming paradigm² that forms the foundation of all modern programming languages in common use today. He also invented the null reference. Please don’t hold that against him, though. He publicly apologized³ for it in 2009, calling it his “billion-dollar mistake.”

Tony Hoare literally invented programming as we know it. So when he says that the single most important property of a program is whether it accomplishes the intention of its user, you can take that on some authority. Think about this for a second: Hoare specifically (and quite rightly) points out that it’s the intention of a program’s users—not its creators—that dictates whether a program is performing correctly. How inconvenient that the intentions of a program’s users aren’t always the same as those of its creator!

Given this assertion, it stands to reason that a user’s first expectation about a program is that the program works. But how do you know that a program is “working”? This is actually a ...