最近有个工作是使用Nginx + Lua实现一个操作MongoDB数据库的API，主要实现其count和query功能。之前没有写过Lua，于是也就勉强着上手，在cloudwu的 lua-mongo 的基础上实现了操作MongoDB的API。

cloudwu的lua-mongo驱动实现了连接Mongo，进行find和findOne等基本操作的功能，所以在lua-mongo的基础上增加了count和query等方法。修改的具体内容如下：

1、API基于luajit-2.0开发，相当于lua 5.1，需要使用lua-compat-5.2兼容lua 5.2

2、使用ngx.socket.tcp替换mongo.socket模块

3、增加了count，query，auth等方法

修改之后的代码见： lua-mongo

具体的操作MongoDB的lua代码如下：
复制代码 代码如下:
-- lua mongo test script
-- utils
function string:split(sep)
  local sep, fields = sep or ":", {}
  local pattern = string.format("([^%s]+)", sep)
  self:gsub(pattern, function(c) fields[#fields + 1] = c end)
  return fields
end
-- 常量
HOST = "127.0.0.1"
PORT = 27017
KEEPALIVE_TIMEOUT = 60000
KEEPALIVE_SIZE = 100
CONN_TIMEOUT = 3000
DB_USER = "user"
DB_PASSWD = "password"
DB_NAME = "blog"
DB_COLLECTION = "article"
-- 引用
mongo = require("mongo")
cjson = require("cjson.safe")
cbson = require("bson")
-- 状态
local status_msg = "error"
local status_code = 500
local message = "unknown error"
local mongo_query = {["category_id"] = {["$in"] = {1,2,3,4}}, ["status"] = {["$ne"] = 2}, ["create_time"] = {["$lte"] = 1427102260}}
local mongo_sort = {["create_time"] = 1}
local mongo_limit = 100
local mongo_skip = 0
local mongo_fields = { ["_id"] = false }
-- 涉及到时间的字段，需要使用bson转化一下
if mongo_query["create_time"] then
  local create_time = mongo_query["create_time"]
  local t = type(create_time)
  if t == "table" then
    for key, value in pairs(create_time) do
      mongo_query["create_time"][key] = cbson.date(value)
    end
  else
    mongo_query["create_time"] = cbson.date(create_time)
  end
end
local conn = mongo.client({ host = HOST, port = PORT })
conn:set_timeout(CONN_TIMEOUT)
local db = conn:getDB(DB_NAME)
local reused_times = conn:get_reused_times()
if reused_times == 0 then
  db:auth(DB_USER, DB_PASSWD)
end
local col = db:getCollection(DB_COLLECTION)
local result = {}
-- count
local count, err = col:count(mongo_query)
local ok, err = conn:set_keepalive(KEEPALIVE_TIMEOUT, KEEPALIVE_SIZE)
if count ~= nil then
  result = count
  status_code = 200
  status_msg = "ok"
  message = "success"
end
-- query
local bson_obj
if mongo_sort then
  bson_obj = cbson.encode_order("$query", mongo_query, "$orderby", mongo_sort)
else
  bson_obj = cbson.encode({ ["$query"] = mongo_query })
end
local results = col:query(bson_obj, mongo_fields, mongo_skip, mongo_limit)
local ok, err = conn:set_keepalive(KEEPALIVE_TIMEOUT, KEEPALIVE_SIZE)
if results then
  for _, object in pairs(results) do
    for key, value in pairs(object) do
      if value == cbson.null then
        object[key] = cjson.null
      else
        local type_name, value = cbson.type(value)
        object[key] = value
      end
    end
  end
  result = results
  status_code = 200
  status_msg = "ok"
  message = "success"
end
-- findOne
local results = col:findOne({["id"] = 14 })
local ok, err = conn:set_keepalive(KEEPALIVE_TIMEOUT, KEEPALIVE_SIZE)
if results then
  for key, value in pairs(results) do
    if value == cbson.null then
      results[key] = cjson.null
    else
      local type_name, value = cbson.type(value)
      results[key] = value
    end
  end
  result = results
  status_code = 200
  status_msg = "ok"
  message = "success"
end
ngx.status = status_code
json_out = cjson.encode({ status = status_msg, message = message, data = result })
ngx.header["Content-Length"] = json_out:len()
ngx.print(json_out)