In my last post I talked about the need to keep things separated once they've been decoupled. Let's look at one of the ways this breaks down: entity services. If a pattern is a solution to a problem in a context, what is an antipattern? An antipattern is a commonly-rediscovered solution to a problem in a context, that inadvertently creates a resulting context we like less than the original context.

Software doesn't have any natural boundaries. There are no rivers, mountains, or deserts to separate different pieces of software. If two services interact, then they have a sort of "attractive force" that makes them grow towards each other. The interface between them becomes more specific. Semantic coupling sneaks in. At a certain point, they might as well be one module running in one process. If you're building microservices, you need to make sure they don't grow together into an impenetrable bramble.

Humans are great storytellers and even better story-listeners. We love to hear stories so much that when there aren't any available, we make them up on our own. From an early age, children grasp the idea of narrative. Even if they don't understand the forms of storytelling so much, you can hear a four-year-old weave a linked list of events from her day. We look for stories behind everything. At a deep level, we want the world's events to mean something.

I’m excited to announce the beta of Release It! Second edition. It’s been ten years since the first edition was released. Many of the lessons in that book hold strong. Some are even more relevant today than in 2007. But a few things have changed. For one thing, capacity management is much less of an issue today. The rise of the cloud means that developers are more exposed to networks than ever.

I’ve come to believe that every system implicitly defines a spectrum of changes, ordered by their likelihood. As designers and developers, we make decisions about what to embody as architecture, code, and data based on known requirements and our experience and intuition. We pick some kinds of changes and say they are so likely that we should represent the current choice as data in the system. For instance, who are the users?

Queues are the enemy of high-velocity flow. When we see them in our software, we know they will be a performance limiter. We should look at them in our processes the same way. I've seen meeting rooms full of development managers with a chart of the year, trying to allocate which week each dev project will enter the QA environment. Any project that gets done too early just has to wait its turn in QA.

Last post covered technical definitions of fault, error, and failure. In this post we will apply these definitions in a system. Our context is a long-running service or server. It handles requests from many different consumers. Consumers may be human users, as in the case of a web site, or they may be other programs. Engineering literature has many definitions of "availability." For our purpose we will use observed availability.

Our systems suffer many insults when they contact the real world. Flaky inputs, unreliable networks, and misbehaving users, to name just a few. As we design our components and systems to thrive in the only environment that matters, it pays to have mental schema and language to discuss the issues. A fault is an incorrect internal state in your software. Faults are often introduced at component, module, or subsystem boundaries.

This is an excerpt from something I'm working on this Labor Day holiday: – Large scale power outages act a lot like software failures. It starts with a small event, like a power line grounding out on a tree. Ordinarily that would be no big deal but under high-stress conditions it can turn into a cascading failure that affects millions of people. We can also learn from how power gets restored after an outage.

Do you remember Digital Audio Tape? DAT was supposed to have all the advantages of digital audio—high fidelity and perfect reproduction—plus the "advantages" of tape. (Presumably those advantages did not include melting on the dashboard of your Chevy Chevelle or spontaneously turning into The Best of Queen after a fortnight.) In hindsight, we can see that DAT was a twilight product. As the sun set on the cassette era, DAT was an attempt to bridge the discontinuous technology change to digital music production.