lua-llthreads2

This is full dropin replacement for llthreads library.

Incompatibility list with origin llthreads library

does not support Lua 5.0
does not support ffi interface (use Lua C API for LuaJIT)
returns nil instead of false on error
start method returns self instead of true on success

Additional

thread:join() method support zero timeout to check if thread alive (does not work on Windows with pthreads)
thread:join() method support arbitrary timeout on Windows threads
thread:alive() method return whether the thread is alive (does not work on Windows with pthreads)
set_logger function allow logging errors (crash Lua VM) in current llthread's threads
thread:start() has additional parameter which control in which thread child Lua VM will be destroyed
allow pass cfunctions to child thread (e.g. to initialize Lua state)

Thread start arguments

`detached`	`joinable`	join returns	child state closes by	gc calls	detach on
false	false	`true`	child	join	`<NEVER>`
false(*)	true(*)	Lua values	parent	join *	`<NEVER>`
true	false(*)	raise error	child	`<NONE>`	start
true	true	`true`	child	detach	gc

Usage

Use custom logger

In this example I use lua-log library.

-- This is child thread.
local llthreads = require "llthreads2"
-- Send logs using ZMQ
local LOG = require"log".new(
  require "log.writer.net.zmq".new("tcp://127.0.0.1:5555")
)
llthread.set_logger(function(msg) LOG.error(msg) end)
-- This error with traceback will be passed to logger
error("SOME ERROR")

Start attached thread collectd in child thread

-- This is main thread.
local thread = require "llthreads2".new[[
  require "utils".sleep(5)
]]

-- We tell that we start attached thread but child Lua State shuld be close in child thread. 
-- If `thread` became garbage in main thread then finallizer calls thread:join() 
-- and main thread may hungup. But because of child state closes in child thread all objects
-- in this state can be destroyed and we can prevent deadlock.
thread:start(false, false)

-- We can call join.
-- Because of Lua state destroys in child thread we can not get 
-- returned Lua values so we just returns `true`.
thread:join()

Start detached joinable thread

-- This is main thread.
local thread = require "llthreads2".new[[
  require "utils".sleep(5)
]]

-- We tell that we start detached joinable thread. In fact we start attached 
-- thread but if `thread` became garbage in main thread then finallizer just 
-- detach child thread and main thread may not hungup.
thread:start(true, true)

-- We can call join.
-- Because of Lua state destroys in child thread we can not get 
-- returned Lua values so we just returns `true`.
thread:join()

Pass to child thread host application`s library loader

If you close parent Lua state then some dynamic library may be unloaded and cfunction in child Lua state (thread) became invalid.

-- `myhost.XXX` modules is built-in modules in host application
-- host application registers cfunction as module loader
local preload = {}
preload[ 'myhost.logger' ] = package.preload[ 'myhost.logger' ]
preload[ 'myhost.config' ] = package.preload[ 'myhost.config' ]
llthreads.new([[
  -- registers preload
  local preload  = ...
  for name, fn in pairs(preload) do package.preload[name] = fn end

  local log = require 'myhost.logger'

]], preload):start(true)

Wait while thread is alive

local thread = require "llthreads2".new[[
  require "utils".sleep(5)
  return 1
]]
thread:start()

-- we can not use `thread:join(0)` because we can not call it twice
-- so all returned values will be lost
while thread:alive() do 
  -- do some work
end

local ok, ret = thread:join() -- true, 1

Use `ex` module

local Threads = require "llthreads2.ex"

local ok, v = Threads.new(function()
  return 1
end):start():join()
assert(v == 1)

local thread = Threads.new({
  -- this thread code gets changed arguments
  function(a, b)
    assert(1 == a)
    assert(2 == b)
    print("Done")
  end;
  
  -- prelude can change thread arguments
  prelude = function(a, b)
    assert("1" == a)
    assert(nil == b)
    return tonumber(a), 2
  end;
}, "1")

thread:start():join()

moteus/lua-llthreads2