连接池还是连接迟？

基于 lua-resty-mongol

学习玩可以，在生产环境测试效果不理想。

缺点：

　　1. 不支持复制集

　　2. 高并发情况下容易 timeout

- mongol_pool.lua

local conf = require "mongol_conf"
local mongol = require("resty.mongol")

local _M = {
	_VERSION = "0.1.0"
}

function _M:new(database)
	_M.database = database or conf.database

	return setmetatable({}, {__index = _M})
end

function _M:get_connect(host, port, timeout)
	local host = host or conf.host
	local port = port or conf.port
	local timeout = timeout or conf.timeout
	if ngx.ctx.mongo_client then
		return ngx.ctx.mongo_client
	end

	local conn = mongol:new()
	if not conn then
		return nil, '### MongoDB initialize failed. ###'
	end

	conn:set_timeout(timeout)

    -- config the ngx.socket.tcp/cosocket built-in connection pool
    -- https://github.com/openresty/lua-nginx-module#ngxsockettcp
    local pool = conf.username..":"..conf.database..":"..conf.host..":"..conf.port
    local pool_size = conf.pool_size
    local backlog = conf.backlog
    local pool_opts = {
        pool = pool,
        pool_size = pool_size,
        -- backlog = backlog
    }
	local ok, err = conn:connect(host, port, pool_opts)
	if not ok then
		return nil, err
	end

	ngx.ctx.mongo_client = conn
	return ngx.ctx.mongo_client,nil
end

function _M:close(keepalive_time, pool_size)
	local keepalive_time = keepalive_time or conf.keepalive_time
	local pool_size = pool_size or conf.pool_size
	if ngx.ctx.mongo_client then
        -- no need to manually call the close method on it afterwards.
		ngx.ctx.mongo_client:set_keepalive(keepalive_time, pool_size)
		ngx.ctx.mongo_client = nil
	end
end

function _M:get_col(colname)
	local conn, err = _M:get_connect()
	if not conn or err then
		return nil, '### MongoDB connect failed: '..err..' ###';
	end

	local database = _M.database or conf.database
	local db = conn:new_db_handle(database)
	if db == nil then
		_M:close()
		return nil, '### MongoDB new_db_handle failed. ###'
	end
    local times,err =conn:get_reused_times()
    if 0 == times or nil == times then
	    local ok, err = db:auth_scram_sha1(conf.username, conf.password)
	    if ok ~= 1 then
	    	_M:close()
	    	return nil, '### MongoDB auth_scram_sha1 failed: '..err.." ###"
	    end
    else
        ngx.log(ngx.ERR, '$$$ reused: ')
        ngx.log(ngx.ERR, times)
    end
	local colname = colname or conf.colname

	return db:get_col(colname),nil
end

return _M

- mongol_conf.lua

local _M = {
    host  = 'your-mongodb-host',
    port = 27017,
    username  = 'standby',
    password = 'standby',
    database = 'standby',
    keepalive_time = 10000,
    pool_size = 100,
    backlog = 100,
    timeout = 10000,
    colname = 'test',
}

return _M