Module: Apartment::Patches::LiveTenantPropagation

Defined in:
lib/apartment/patches/live_tenant_propagation.rb

Overview

Backports rails/rails#56902 (“Pass IsolatedExecutionState.context to share_with”) to Rails versions where the fix has not landed.

On Rails 7.2 / 8.0 / 8.1.x stable, ActionController::Live#process calls ActiveSupport::IsolatedExecutionState.share_with(Thread.current, …) which reads from Thread.current.active_support_execution_state. Under :fiber isolation that’s empty — the data lives on Fiber.current’s accessor. The spawned thread’s root fiber starts with empty state and any CurrentAttributes set on the request fiber are invisible inside response.stream.write — silent cross-tenant data exposure.

The fix: before Live#process spawns the streaming thread, point Thread.current.active_support_execution_state at the same hash Fiber.current.active_support_execution_state points at. share_with’s shallow .dup then copies the right data into the spawned thread’s root fiber. Restore Thread’s prior state on exit.

Mechanically equivalent to what rails/rails#56902 does on main: capture IsolatedExecutionState.context (= Fiber.current under :fiber) and pass it to share_with. Apartment can’t edit Rails source from inside a gem, but a temporary mirror feeds share_with the right pointer with the same end result.

No-op under :thread isolation (Rails’ own propagation already works there). No-op when Fiber.current.active_support_execution_state is nil (no CurrentAttributes have been touched on this fiber yet, so there is nothing to propagate).

See docs/designs/rails-boundary-tenancy.md.

Instance Method Summary collapse

Instance Method Details

#process(name) ⇒ Object 



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# File 'lib/apartment/patches/live_tenant_propagation.rb', line 37

def process(name)
  return super unless ActiveSupport::IsolatedExecutionState.isolation_level == :fiber

  fiber_state = Fiber.current.active_support_execution_state
  return super if fiber_state.nil?

  previous_thread_state = Thread.current.active_support_execution_state
  Thread.current.active_support_execution_state = fiber_state
  begin
    super
  ensure
    Thread.current.active_support_execution_state = previous_thread_state
  end
end