Chapter 9. Isolating error effects
This chapter covers
- Understanding supervision trees
- Starting workers dynamically
- “Let it crash”
In chapter 8, you learned about the basic theory behind error handling in concurrent systems based on the concept of supervisors. The idea is to have a process whose only job is to supervise other processes and to restart them if they crash. This gives you a way to deal with all sorts of unexpected errors in your system. Regardless of what goes wrong in a worker process, you can be sure that the supervisor will detect an error and restart the worker.
In addition to providing basic error detection and recovery, supervisors play an important role in isolating error effects. By placing individual workers directly under a supervisor, you can confine an error’s impact to a single worker. This has an important benefit: it makes your system more available to its clients. Unexpected errors will occur no matter how hard you try to avoid them. Isolating the effects of such errors allows other parts of the system to run and provide service while you’re recovering from the error.