JavaScript: Functional Programming for JavaScript Developers

Circuit breaker pattern

Systems, even the best designed systems, fail. The larger and more distributed a system, the higher the probability of failure. Many large systems such as Netflix or Google have extensive built-in redundancies. The redundancies don't decrease the chance of a failure of a component but they do provide a backup. Switching to the backup is frequently transparent to the end user.

The circuit breaker pattern is a common component of a system that provides this sort of redundancy. Let's say that your application queries an external data source every five seconds, perhaps you're polling for some data that you're expecting to change. What happens when this polling fails? In many cases the failure is simply ignored and the polling ...