1. lua模块demo（redis，http，mysql，cjson，本地缓存）

1.1. 配置

1. 在nginx.conf中设置lua_shared_dict my_cache 128m; 开启nginx本地缓存，放到http{} 层
2. location配置

location /redis-get{
    resolver 8.8.8.8;
    default_type text/html;
    content_by_lua_file /usr/local/openresty/lua/redis-get.lua;
}

1. 这里推荐个工具，使用notepad++，下载个插件NppFtp，效果如下图，可以直接对liunx上的文件进行编辑保存

1.2. http

1. 远程调用可以使用该模块 https://github.com/ledgetech/lua-resty-http
2. 把lib包里的两个文件复制到 /usr/local/openresty/lualib/resty
3. 通过require("resty.http") 调用

1.3. mysql

1. 连接工具

local connectMysqlUtil = {}

local mysql = require "resty.mysql"
-- connect to mysql;
function connectMysqlUtil.connect()
    local db, err = mysql:new()
    if not db then
        return false
    end
    db:set_timeout(1000)
    
    local ok, err, errno, sqlstate = db:connect{
        host = "127.0.0.1",
        port = 8083,
        database = "test",
        user = "dev",
        password = "1234",
        max_packet_size = 1024 * 1024 }
    
    if not ok then
        ngx.say("connect mysql failed")
        return false
    end
    return db
end

return connectMysqlUtil

参考 https://www.cnblogs.com/zhuzi91/p/7879956.html

1.4. string工具

local stringEx = {}

function stringEx.ToStringEx(value)
    if type(value)=='table' then
       return stringEx.TableToStr(value)
    elseif type(value)=='string' then
        return "\'"..value.."\'"
    else
       return tostring(value)
    end
end

function stringEx.TableToStr(t)
    if t == nil then return "" end
    local retstr= "{"

    local i = 1
    for key,value in pairs(t) do
        local signal = ","
        if i==1 then
          signal = ""
        end

        if key == i then
            retstr = retstr..signal..stringEx.ToStringEx(value)
        else
            if type(key)=='number' or type(key) == 'string' then
                retstr = retstr..signal..'['..stringEx.ToStringEx(key).."]="..stringEx.ToStringEx(value)
            else
                if type(key)=='userdata' then
                    retstr = retstr..signal.."*s"..stringEx.TableToStr(getmetatable(key)).."*e".."="..stringEx.ToStringEx(value)
                else
                    retstr = retstr..signal..key.."="..stringEx.ToStringEx(value)
                end
            end
        end

        i = i+1
    end

     retstr = retstr.."}"
     return retstr
end

function stringEx.StrToTable(str)
    if str == nil or type(str) ~= "string" then
        return
    end
    
    return loadstring("return " .. str)()
end

return stringEx

1.5. 整合redis+本地缓存

-- 自定义的字符串转换工具
local stringEx = require("stringExt")

-- 本地缓存
local local_cache = ngx.shared.my_cache

-- redis连接池，设置连接空闲时间
local function close_redis(red)
    if not red then
        return
    end
    local pool_max_idle_time = 10000
    local pool_size = 100
    local ok,err = red:set_keepalive(pool_max_idle_time,pool_size)
    if not ok then
        ngx.say("set keepalive fail ",err)
    end
end

-- 读redis缓存
local function read_redis(key)
    local redis = require("resty.redis")
    local red = redis.new();
    local ok,err = red:connect("127.0.0.1",8084)
    if not ok then 
        ngx.say("connect fail ",err)
        return close_redis(red)
    end
    red:set_timeout(1000)

    local count,err = red:get_reused_times()
    if 0==count then
        ok,err = red:auth("123456")
        if not ok then
            ngx.say("auth fail ",err)
            return close_redis(red)
        end
    elseif err then
        ngx.say("fail to get reused times")
        return close_redis(red)
    end

    local res,err = red:get(key)
    if not res then
        ngx.say("get msg fail ",err)
        return close_redis(red)
    elseif res then
        ngx.say(" set expire 10000 ")
        red:expire(key,10)
    end
    local_cache:set(key,res,5)
    ngx.say("read from redis ")
    ngx.say(res)
    close_redis(red)
end

-- http请求参数
local args = ngx.req.get_uri_args()
local key = args["key"]
if not key then 
    ngx.say("key must be exist")
    return
end

local keyCache = local_cache:get(key)
if not keyCache then
    local res = read_redis(key)
    if not res then
        ngx.say("redis is null")
    end
else
    ngx.say("read from localCache ")
    ngx.say(keyCache)
end

-- http调用工具，需要额外下载，地址：https://github.com/ledgetech/lua-resty-http 说明：https://blog.csdn.net/xiejunna/article/details/53445342
local http = require("resty.http")
local httpc = http.new();
if not httpc then 
    ngx.say("\n\r httpc new fail")
end
httpc:set_timeout(8000)
-- keepalive参数不写可能导致报错
local res,err = httpc:request_uri("http://www.xxx.com",{
    method="POST",
    path="/xxx/rpc.api",
    body = 'a=1&b=2',
    headers = {
          ["Content-Type"] = "application/x-www-form-urlencoded",
        },
    keepalive_timeout = 60,
    keepalive_pool = 10
})
if not res then
    ngx.say("httpc call fail ")
    return
end
local cjson = require("cjson")
local json = cjson.new()
if not json then
    ngx.say("json is null")
    return
end

-- 测试调用结果
-- ngx.say(stringEx.TableToStr(res))
-- ngx.say(stringEx.ToStringEx(json.decode(res["body"])))
-- ngx.say(type(json.decode(res["body"])))
-- ngx.say(stringEx.ToStringEx(json.decode(res["body"])["header"]["request_seq"]))
-- ngx.say(type(json.decode(res["body"])["header"]))
-- ngx.say(type(json.decode(res["body"])["header"]["request_seq"]))

local connectMysqlUtil = require("connectMysqlUtil")
local db = connectMysqlUtil.connect()
if not db then
    ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
    return
end

local res,err,errcode,sqlstate = db:query("select * from t_uls_order_info where order_id='20190119232946000023'",10)
if not res then
    ngx.say("bad request: ",err,":",errcode,": ",sqlstate,".")
    return
end

ngx.say("result:",json.encode(res))

1.6. 总结

1. 本文记录了对http，mysql，redis，nginx本地缓存的基本使用方式，后续需要使用到该模块的需求可以直接参考修改本示例代码
2. 对于实际的互联网需求，这里可以想象个基于这些模块的需求，优先读取ngnix本地缓存，过期时间较短，其次读取redis缓存，减少redis压力，进一步减少mysql读取压力