Errors happen. Code has bugs. Hardware, software, and networks are unreliable. Failures happen for all types of applications, not just for microservices. But microservices applications are more complex, and so problems can become considerably worse as we grow our application. The more microservices we maintain, the greater the chance at any given time that some of those microservices will be misbehaving!
We can’t avoid problems entirely. It doesn’t matter if these are caused by human error or unreliable infrastructure. It’s a certainty-problems happen. But just because problems can’t always be avoided, doesn’t mean we shouldn’t try to mitigate against these. A well-engineered application anticipates and accounts for problems, even when the specific nature of some problems can’t be anticipated.
As our application evolves to be more complex, we’ll need techniques to combat problems and keep our microservices healthy. Our industry has developed many “best” practices and patterns for dealing with problems. We’ll cover some of the most useful ones in this chapter. Following this guidance will make your application run more smoothly and be more reliable, resulting in less stress and easier recovery from problems when they do happen.