Question

我正在尝试使用服务器套接字实现一个脚本，该脚本还会定期轮询来自多个传感器的数据（即每分钟59秒）。我不想将数据序列化到磁盘，而是将其保存在套接字将在轮询时响应的表中。这里有一些草图代码来说明我想要做的事情（我没有包含访问此服务器的客户端代码，但该部分没问题）

#!/usr/bin/env lua

local socket = require("socket")
local server = assert(socket.bind("*", 0))
local ip, port = server:getsockname()

local data = {}
local count = 1
local function pollSensors()
  -- I do the sensor polling here and add to table e.g os.time()
  table.insert(data, os.time() .."\t" .. tostring(count))
  count = count + 1
end

while true do
  local client = server:accept()
  client:settimeout(2)
  local line, err = client:receive()
  -- I do process the received line to determine the response
  -- for illustration I'll just send the number of items in the table
  if not err then client:send("Records: " ..table.getn(data) .. "\n") end
  client:close()
  if os.time().sec == 59 then
     pollSensors()
  end
end

我担心服务器有时会阻塞，因此我会错过第59秒。

这是实现这个的好方法还是有一个（更简单）更好的方法（比如使用协程）？如果协同程序会更好，我该如何为我的场景实现它们？

Answer 1

要实现这一目标，您需要某种多任务处理。我使用网络感知调度程序。

e.g。 cqueues看起来像这样：

local cqueues = require "cqueues"
local cs = require "cqueues.socket"

local data = {}
local count = 1
local function pollSensors()
    -- I do the sensor polling here and add to table e.g os.time()
    table.insert(data, os.time() .."\t" .. tostring(count))
    count = count + 1
end

local function handle_client(client)
    client:setmode("b", "bn") -- turn on binary mode for socket and turn off buffering
    -- ported code from question:
    client:settimeout(2) -- I'm not sure why you chose a 2 second timeout
    local line, err = client:read("*l") -- with cqueues, this read will not block the whole program, but just yield the current coroutine until data arrives.
    -- I do process the received line to determine the response
    -- for illustration I'll just send the number of items in the table
    if not err then
        assert(client:write(string.format("Records: %d\n", #data)))
    end
    client:close()
end

local cq = cqueues.new() -- create a new scheduler
-- create first coroutine that waits for incoming clients
cq:wrap(function()
    local server = cs.listen{host = "0.0.0.0"; port = "0"}
    local fam, ip, port = server:localname()
    print(string.format("Now listening on ip=%s port=%d", ip, port))
    for client in server:clients() do -- iterates over `accept`ed clients
        -- create a new coroutine for each client, passing the client in
        cqueues.running():wrap(handle_client, client)
    end
end)
-- create second coroutine that reads sensors
cq:wrap(function()
    while true do
        -- I assume you just wanted to read every 60 seconds; rather than actually *on* the 59th second of each minute.
        pollSensors()
        cqueues.sleep(60)
    end
end)
-- Run scheduler until all threads exit
assert(cq:loop())

Answer 2

我认为使用不同语言的“cron”库可以很好地实现定期启动一些应用程序/代码。例如，lua中的cron lib可以下载here。

Lua - Socket接收带有其他事件的计时器

2 个答案: