Stateful Apps

We briefly introduced the concept of statefulness in Chapter 12, Your Application and HA. Stateful components of applications are a necessity to just about all information technology systems in the world. They're necessary to keep account details, records of transactions, information on HTTP requests, and a whole host of other purposes. The challenging part of running these applications in a production environment almost always has to do with either the network or the persistence mechanism. Whether it's spinning metal disks, flash storage, block storage, or some other yet-to-be-invented tool, persistence is notoriously difficult to deal with in all forms. Part of why this is difficult is because all of these forms have a non-zero probability of failure, which can become very significant once you need to have hundreds or even thousands of storage devices in a production environment. These days, many cloud providers will give assistance to customers and offer...