Ruby methods are colorless
Debate over Ruby’s “colorless” concurrency model highlights a broader split in how languages handle async work. Many developers argue that explicit async/await and “colored” functions (as in JavaScript, C#, Rust) make I/O boundaries, latency and potential yield points clearer, aiding reasoning and performance tuning, especially in UIs and network-heavy code. Others prefer Ruby-, Go- or Erlang-style models where scheduling is handled by the runtime and call sites stay syntactically uniform, warning that pervasive async coloring complicates APIs, refactoring and long‑lived codebases without solving the hardest concurrency and parallelism problems.
Ruby’s “colorless” concurrency
- Ruby hides async behavior behind threads and fibers, so most methods look synchronous.
- Fibers plus a scheduler can make many IO operations non-blocking without changing method signatures.
- Some see this as elegant and ergonomic; others warn it hides when code blocks or yields, making reasoning about performance and contention harder.
- Ruby’s GVL limits true parallelism in MRI for CPU-bound code; Ractors or alternative runtimes (JRuby) are suggested for real parallelism.
Async/await and function coloring
- Many comments revisit “function coloring”: async functions returning promises/tasks vs sync ones.
- Critics: coloring forces async all the way up the call stack, leads to duplicated “sync vs async” APIs, complicates refactors, and exposes single-threaded runtimes into user code.
- Supporters: coloring is a feature; it advertises where IO and yields happen, like a lightweight effect system or Rust’s borrow checker for concurrency.
- Several note that upgrading legacy callback-based code to async/await is painful.
Comparisons across languages
- JavaScript: async/await seen as sugar over promises to avoid callback hell, but also as a new “hell” in large codebases.
- Go: goroutines and channels give colorless concurrency, but boilerplate (channels, WaitGroups) and error handling are highlighted; structured concurrency libraries exist.
- C#, Kotlin, Rust, Python: all have colored async; discussion of dual sync/async APIs, cancellation, and structured concurrency.
- Haskell/Scala: cited as examples of “polymorphic over async” via monads; same code can be sync or async depending on the effect type.
- Erlang/Elixir: actor model and preemptive scheduling sidestep much of the coloring debate.
Use cases and performance
- Async/await praised for high-concurrency IO workloads (scrapers, HTTP services, UI latency) and for making potential parallelism visible.
- Others argue threads or actor/message-passing models remain simpler and more robust for many server workloads.
- Game-dev and UI discussions emphasize scheduling, frame deadlines, and that yielding on IO is often unacceptable in real-time loops.
Tooling, API design, and ambiguity
- Several stress IDE support and type annotations as ways to surface async behavior without syntax noise.
- API evolution issues: once a function is async, it tends to stay that way even if internals change.
- No consensus: some prefer explicit async markers; others prefer colorless models with stronger runtimes or richer type systems.