Ractor¶

Give TIMEx a pure-ish CPU chunk, ship it to a Ractor, and wait—up to your deadline—for an answer. If the clock wins first, TIMEx walks away: the Ractor keeps chewing in the background and its result is dropped.

Mental model: texting a friend for trivia at a bar quiz. If they reply before last call, great. If not, you guess yourself—they might still text you later, but you are not waiting at the door.

Quick example¶

TIMEx.deadline(2.0, strategy: :ractor) { pure_function(input) }

Keep the block shareable and side-effect light—Ractors still have sharp edges in Ruby.

At a glance¶

Topic	Plain English
CPU-heavy work	No hard stop inside the Ractor if you time out—the work may finish anyway.
Blocking IO	Same story: you stopped waiting, not the syscall.
Mutexes / shared state	Safer than threads for isolation—Ractors do not share mutable soup by default.
Ruby version	Same baseline as the gem (3.3+ today). Ractors remain experimental in MRI—ship with extra paranoia.

When this actually helps¶

Optional speculative compute (prefetch, warm cache) where losing the result is fine because another code path covers you.
CPU-only embarrassingly parallel helpers that never touch the outside world.

When to pick something else¶

If you must reclaim CPU when time is up, use Subprocess so the OS can actually evict the work.

Real-world: speculative cache warm on a product page¶

The product page already has the data it needs from Postgres. While the template renders, you would like to pre-decode a related-products JSON blob into the cache—but only if it finishes in under 50 ms. Past that, the page ships without it and the next request can warm the cache itself:

def related_products_warm!(product_id, blob)
  TIMEx.deadline(0.05, strategy: :ractor, on_timeout: :return_nil) do
    parsed = JSON.parse(blob, symbolize_names: true)
    Rails.cache.write("related:#{product_id}", parsed, expires_in: 5.minutes)
    parsed
  end
end

If 50 ms is not enough this time, the ractor keeps parsing in the background (telemetry emits ractor.leak) and your request returns nil instead of waiting—exactly the trade-off speculative work is supposed to make.