What are the best practices for using async in Haskell?

What are the best practices for using async in Haskell?

When using async in Haskell, it's important to manage resources effectively. Here are some best practices:

1. Use async for concurrent tasks that can run independently.
2. Always handle exceptions using waitCatch to avoid unhandled exceptions.
3. Limit the number of concurrent threads to prevent resource exhaustion.
4. Use withAsync for scoped async operations to ensure proper cleanup.

Can you explain how to handle exceptions with async?

Certainly! To handle exceptions in async operations, you can use waitCatch instead of wait. This function returns an Either type, allowing you to distinguish between a successful result and an exception. Here's a simple example:

result <- waitCatch myAsyncAction
case result of
    Left ex -> putStrLn $ "Caught exception: " ++ show ex
    Right value -> putStrLn $ "Result: " ++ show value

What about limiting the number of concurrent threads?

You can limit the number of concurrent threads by using a semaphore or a bounded queue. For example, you can use the Control.Concurrent.Semaphore module to create a semaphore that restricts the number of concurrent actions. This helps prevent resource exhaustion and keeps your application responsive.

Are there any libraries that can help with async in Haskell?

Yes, there are several libraries that can help with async programming in Haskell. The most popular one is the async library, which provides abstractions for concurrent programming. Additionally, libraries like stm (Software Transactional Memory) can help manage shared state in a concurrent environment.