- Multithreading and concurrency is a difficult topic, and our goal as developers is to predict the possible problems on the design stage of development.
- Many different problems occur in a inaccurately crafted concurrent environment: dead locks, threads starvation, resource leackage or wrong disposal.
- Learn the difference between IORefs, MVars and STM TVars in a concurrent environment so you could consciously choose between them to design a reliable concurrent code.
- TVars are thread-save and transactional, and also they are fundamental because you can express other data structures with them.
- Try to organize your threads safely to avoid leakage of handlers or other concurrent problems.
- Transactional data structures represent a data model, transactions (funtions within the STM monad) represent a behavior model.
- Normally, bare threads should be treated as a limited resource, even if they are green.
- Leakage of green threads is a less sharp problem than leakage of OS-specific threads, but still is not desirable from the design point of view.
- Free monads can be your architectural pattern for constructing a general-purpose application framework.
- Incorporating STM into the framework as an interface brings another state handling mechanism for the business logic.
- STM on the implementation layer can and will make the framework safely concurrent.
- Bare IO is a temptation for developers, so it’s better to put it (IO, not developers) in a straitjacket
