haproxy-agent.lua

#!/usr/bin/env lua

local socket = require("socket")
local signal = require("posix.signal")

local cfg = {}
local reload_cfg_interval = 1
local socket_timeout = 10
local status_file = "haproxy-agent.conf"

local host = os.getenv("HOST") or "0.0.0.0"
local port = tonumber(os.getenv("PORT")) or 9090
local sock, err = socket.bind("0.0.0.0", port)
if sock then
  print(string.format("haproxy-agent listening on %s:%d", host, port))
else
  print(string.format("can't bind to socket with %s:%d, please check", host, port))
  os.exit(2)
end

--[[
--example config
ready up maxconn:30 0% # test
myservice.paulbsd.com: ready up 93% maxconn:15
--]]--

local cfg_loader = coroutine.create(function()
  while true do
    cfg = get_cfg()
    coroutine.yield()
  end
end)

function get_cfg()
  local res = {}
  local lines = io.lines(status_file)
  for line in lines do
    local s, e, key, value = string.find(line, "([%w%p]+): ([%w %p]+)")
    if value then
      res[key] = value
    else
      local s, e, value = string.find(line, "([%w %p]+)")
      if value then
        res["all"] = value
      end
    end
  end
  return res
end

function close(conn)
  conn:close()
  conn:shutdown()
end

function run()
  while true do
      local conn = sock:accept()
      conn:settimeout(socket_timeout)
      local s, e = conn:receive("*l")
      if e == "timeout" then close(conn) coroutine.yield() end
      if s and e ~= "closed" then
        local send = ""
        if cfg[s] then
          send = cfg[s]
        elseif cfg["all"] then
          send = cfg["all"]
        end
        conn:send(send.."\n")
      end
      close(conn)
      coroutine.yield()
  end
end

local runner = coroutine.create(function() run() end)
local last_time = os.time()
coroutine.resume(cfg_loader)

signal.signal(signal.SIGINT, function(signum)
  if sock then sock:close() end
  os.exit(128+signum)
end)

while true do
  coroutine.resume(runner)
  if os.time()-last_time > reload_cfg_interval then
    coroutine.resume(cfg_loader)
    last_time = os.time()
  end
end