Closeable

Some blocking calls only wake up when their handle dies. Closeable wraps a resource (socket, DB connection, anything with a close that interrupts the read) and, on expiry, closes it so the blocked syscall returns with a normal IO error—no Thread#raise required.

Mental model: instead of shaking someone awake, you gently turn off the lamp they were staring at. The room handles the interrupt for you.

Quick example

TIMEx::Strategies::Closeable.new(resource: socket).call(deadline: 2.0) do |io, d|
  io.read(1024)
end

After a timeout-driven close, treat that handle as toast—do not put it back in a pool unless your pool knows how to vet dead connections.

At a glance

Topic	Plain English
CPU-heavy Ruby	Not the target—still need checkpoints for pure Ruby loops.
Blocking IO	Yes: closing wakes many blocking reads/writes cleanly.
Mutexes / shared state	Safer than async exceptions: you get predictable IO errors.
C extensions	Often works when the ext is just wrapping a real fd.
Side effect	The resource is closed—plan on opening a fresh one next time.

When it fits

• Connections you would throw away on timeout anyway.
• Pooled resources—pair with pool.remove(conn) (or your pool’s equivalent) in ensure so zombies never re-enter rotation.

Real-world: a stuck Postgres query in a Rails request

You ran the perfect plan in dev; in prod the same query sometimes pins a connection for minutes behind a missing index. Closeable closes the raw socket so the blocked PG::Connection#exec returns with PG::ConnectionBad instead of holding the request hostage, and you discard the connection so the pool refills with a healthy one:

def find_with_deadline(sql, deadline:)
  ActiveRecord::Base.connection_pool.with_connection do |conn|
    socket = conn.raw_connection.socket_io
    TIMEx::Strategies::Closeable.new(resource: socket).call(deadline: deadline) do |_io, _d|
      conn.exec_query(sql)
    end
  rescue PG::ConnectionBad
    ActiveRecord::Base.connection_pool.remove(conn)
    raise TIMEx::Expired.new("postgres query exceeded deadline", strategy: :closeable)
  end
end

The runaway query stops eating CPU on the database, the pool stays healthy, and the controller gets a normal exception instead of a 30-second hang.