新入门openresty, 对线程模型openresty有些不解，求教

wisdom71036 · 2017-08-19T10:24:39+00:00

Hi folks, I am excited to announce the new formal release, 1.11.2.5, of the OpenResty web platform based on NGINX and LuaJIT: https://openresty.org/en/...

新入门openresty, 对线程模型openresty有些不解，求教

wisdom71036

学习openresty中，对访问module对象有些疑问，比如：

account.lua:

local _M = {}

local c = {}

local i = 0

function _M.new (self)
    if c.index == nil then
        ngx.sleep(0.1)
        i = i+1
        ngx.log(ngx.NOTICE, "setting..."..i)
        c.index = i
    else
        ngx.log(ngx.NOTICE, "index is "..c.index)
    end
end

return _M

accounttest.lua:

local account = require("account")

local a = account:new()

nginx.conf lua_code_cache on.

执行ab -n 5 -c 5 -k -r "http://127.0.0.1/accounttest" 的结果是

2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:22: new(): setting...2, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:22: new(): setting...3, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:22: new(): setting...4, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:22: new(): setting...5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

问题是，我一直认为nginx是单线程模型，然而在并发访问时看上去5个request都同时读到了c.index == nil, 从而都去做setting初始化了。i=i+1却工作正常。本来suppose这样的返回结果：

2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

如果这是正确的结果，求教如果初始化开销很大，如何实现module初始化一次？即保证c.index setting一次。求教！

spacewanderlzx

因为 ngx.sleep(0.1) 这里会切换当前执行的协程（换句话说，当前执行的请求改变了），
所以5个request都同时读到了c.index == nil。

如果模块初始化不能放到 init_by_lua* 之类的阶段执行(比如需要使用 cosocket 接口跟外部交互），你可以用 lua-resty-core 和 ngx.worker.id()，给每个 worker 分配一把锁。
或者，如果你能保证整个初始化过程中不会调用 cosocket 或 ngx.sleep 这样的操作，也可以省下这把锁。

在 2017年8月19日星期六 UTC+8上午10:24:39，wisdo...@gmail.com写道：

学习openresty中，对访问module对象有些疑问，比如：
account.lua:
local _M = {} local c = {} local i = 0 function _M.new (self) if c.index == nil then ngx.sleep(0.1) i = i+1 ngx.log(ngx.NOTICE, "setting..."..i) c.index = i else ngx.log(ngx.NOTICE, "index is "..c.index) end end return _M
accounttest.lua:
local account = require("account") local a = account:new()
nginx.conf lua_code_cache on.
执行ab -n 5 -c 5 -k -r "http://127.0.0.1/accounttest" 的结果是
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:22: new(): setting...2, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:22: new(): setting...3, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:22: new(): setting...4, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:22: new(): setting...5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

问题是，我一直认为nginx是单线程模型，然而在并发访问时看上去5个request都同时读到了c.index == nil, 从而都去做setting初始化了。i=i+1却工作正常。本来suppose这样的返回结果：
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

如果这是正确的结果，求教如果初始化开销很大，如何实现module初始化一次？即保证c.index setting一次。求教！

spacewanderlzx

补充一点，如果模块初始化的过程中不会用到 cosocket/ngx.sleep 这一类导致协程切换的操作，另外又想达到动态初始化的目的，还有一种方法是把 _M.new()

 的调用放到模块里面。像这样：

_M.new()

return _M

由于通过 require 加载的模块会被缓存起来，所以 require 操作只会执行一次，进而保证模块只会被初始化一次。
需要注意 require 里面不支持协程切换的操作。

wisdom71036

谢谢，确实如你所说。

On Saturday, August 19, 2017 at 6:15:14 PM UTC+8, Zexuan Luo wrote:

补充一点，如果模块初始化的过程中不会用到 cosocket/ngx.sleep 这一类导致协程切换的操作，另外又想达到动态初始化的目的，还有一种方法是把 _M.new()的调用放到模块里面。像这样：
_M.new()
return _M 由于通过 require 加载的模块会被缓存起来，所以 require 操作只会执行一次，进而保证模块只会被初始化一次。需要注意 require 里面不支持协程切换的操作。

ssdrliu

有个疑问，5个请求为何打出了10条日志？

在 2017年8月19日星期六 UTC+8上午10:24:39，wisdo...@gmail.com写道：

学习openresty中，对访问module对象有些疑问，比如：
account.lua:
local _M = {} local c = {} local i = 0 function _M.new (self) if c.index == nil then ngx.sleep(0.1) i = i+1 ngx.log(ngx.NOTICE, "setting..."..i) c.index = i else ngx.log(ngx.NOTICE, "index is "..c.index) end end return _M
accounttest.lua:
local account = require("account") local a = account:new()
nginx.conf lua_code_cache on.
执行ab -n 5 -c 5 -k -r "http://127.0.0.1/accounttest" 的结果是
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:22: new(): setting...2, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:22: new(): setting...3, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:22: new(): setting...4, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:22: new(): setting...5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

问题是，我一直认为nginx是单线程模型，然而在并发访问时看上去5个request都同时读到了c.index == nil, 从而都去做setting初始化了。i=i+1却工作正常。本来suppose这样的返回结果：
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

如果这是正确的结果，求教如果初始化开销很大，如何实现module初始化一次？即保证c.index setting一次。求教！

734819342

额. 这是必然,ngx.sleep(0.1)会导致nginx转身去处理其他request...

binnn

Sender: 牧童
Send Time: 2017-09-12 10:52
Receiver: openresty
Subject: [openresty] Re: 新入门openresty, 对线程模型openresty有些不解，求教
有个疑问，5个请求为何打出了10条日志？

在 2017年8月19日星期六 UTC+8上午10:24:39，wisdo...@gmail.com写道：
学习openresty中，对访问module对象有些疑问，比如：
account.lua:
local _M = {} local c = {} local i = 0 function _M.new (self) if c.index == nil then ngx.sleep(0.1) i = i+1 ngx.log(ngx.NOTICE, "setting..."..i) c.index = i else ngx.log(ngx.NOTICE, "index is "..c.index) end end return _M
accounttest.lua:
local account = require("account") local a = account:new()
nginx.conf lua_code_cache on.
执行ab -n 5 -c 5 -k -r "http://127.0.0.1/accounttest" 的结果是
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:22: new(): setting...2, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:22: new(): setting...3, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:22: new(): setting...4, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:22: new(): setting...5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *4 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *1 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *2 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 5, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

问题是，我一直认为nginx是单线程模型，然而在并发访问时看上去5个request都同时读到了c.index == nil, 从而都去做setting初始化了。i=i+1却工作正常。本来suppose这样的返回结果：
2017/08/19 09:40:44 [notice] 9718#4340731: *3 [lua] account.lua:22: new(): setting...1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"
2017/08/19 09:40:44 [notice] 9718#4340731: *5 [lua] account.lua:25: new(): index is 1, client: 127.0.0.1, server: buybox.coupang.com, request: "GET /clustertest HTTP/1.0", host: "127.0.0.1"

如果这是正确的结果，求教如果初始化开销很大，如何实现module初始化一次？即保证c.index setting一次。求教！
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