Chapter 7. Completing the worker-pool application
This chapter covers
- Implementing the entire worker pool application
- Building multiple supervision hierarchies
- Dynamically creating Supervisors and workers
In this chapter, you’ll continue to evolve the design of the Pooly application, which you started in chapter 6. By the end of this chapter, you’ll have a full, working worker-pool application. You’ll get to explore the Supervisor API more thoroughly and also explore more advanced (read: fun!) Supervisor topics.
In chapter 6, you were left with a rudimentary worker-pool application, if we can even call it that. In the following sections, you’ll add some smarts to Pooly. For example, there’s currently no way to handle crashes and restarts gracefully. The current version of Pooly can only handle a single pool with a fixed number of workers. Version 3 of Pooly will implement support for multiple pools and a variable number of worker processes.
Sometimes the pool must deal with an unexpected load. What happens when there are too many requests? What happens when all the workers are busy? In version 4, you’ll make pools that are variable in size and allow for the overflowing of workers. You’ll also implement queuing for consumer processes when all workers are busy.