Lua Multitasking Environment.
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Lumen: Lua Multitasking Environment.

"A nice generic framework to develop complex, portable concurrent applications in Lua."


Lumen is a very simple environment for coroutine based multitasking. Consists of a scheduler, and that's it. The API was inspired by a brief description of Sierra's scheduler. Lumen has no external dependencies nor C code, and runs on unmodified Lua (works with Lua 5.1, 5.2 and LuaJIT). Tasks that interface with LuaSocket and nixio for socket and async file I/O support are provided.

Lumen's API reference is available online. Notice that this is a second generation API (2.0). If you come from the past and are interested in the old Lumen, check the "v1.0" branch.

WARNING: Lumen is under heavy development, and API changes happen rather frequently, as other weird breakages.

How does it look?

Here is a small program, with two tasks: one emits ten numbered signals, one second apart. Another tasks receives those signals and prints them.

    local sched=require 'lumen.sched'

    -- task receives signals
    	local waitd = {'an_event'}
    	while true do
    		local _, data = sched.wait(waitd)
    -- task emits signals
    	for i = 1, 10 do
    		sched.signal('an_event', i)


Tasks can emit signals, and block waiting for them, and that's it.

  • A signal can be of any type, and carry any parameters
  • A task can wait on several signals, with an optional timeout.
  • Signals can be buffered; this helps avoid losing signals when waiting signals in a loop.
  • There is an catalog that can be used to simplify sharing data between tasks.

Pipes & Streams

There are also pipes and streams, for intertask communications.

  • Unlike with plain signals, writers can get blocked too (when pipe or stream gets full).
  • Synchronous and asynchronous (with a timeout) modes supported.
  • Multiple readers and writers supported.
  • For when no signal can get lost!


There are cases when you must guarantee that only one task is accessing a piece of code at a time. Mutexes provide a mechanism for that. Notice that Lumen, being a cooperative scheduler, will never preempt control from a task. That means you only may have to resort to mutexes when your critical piece of code relinquish control explicitly, for example with a call to sleep, emitting a signal or blocking waiting for a signal.


There are a few other useful modules, like an integrated remote Lua shell and a lightweigth HTTP server.

How to try it out?

There several test programs in the tests/ folder. This example has a few tasks exchanging messages, showing off basic functionality:

lua test.lua


Same as Lua, see COPYRIGHT.


Copyright (C) 2012 Jorge Visca,


Andrew Starks (@andrewstarks)