[总结]openresty 限流count.lua:53:attempt to call method 'expire' (a nil value)报错排查

        最近在研究openresty 1.13.6.1版本限流方案，参考该文档：https://github.com/openresty/lua-resty-limit-traffic/blob/master/lib/resty/limit/count.md 编写了一个时间窗内调用总次数限流Demo，可是测试时，遇到如下问题：

2018/03/20 12:38:05 [error] 33074#814554: *1 lua entry thread aborted: runtime error: ...l/Cellar/openresty/1.13.6.1/lualib/resty/limit/count.lua:53: attempt to call method 'expire' (a nil value)

stack traceback:

coroutine 0:

...l/Cellar/openresty/1.13.6.1/lualib/resty/limit/count.lua: in function 'incoming'

conf/limit_frequency.lua:18: in function 'incoming'

...IdeaProjects/luaapp/work/conf/access_limit_frequency.lua:8: in function <...IdeaProjects/luaapp/work/conf/access_limit_frequency.lua:1>, client: 10.202.97.23, server: , request: "GET /limitFrequency HTTP/1.1", host: "10.202.97.23:8080"

报错的直接原因是：openresty/1.13.6.1/lualib/resty/limit/count.lua:53: attempt to call method 'expire' (a nil value)

当时把该错误google了一把，没有找到任何解决方法。于是乎把该错误发到google 讨论组里，https://groups.google.com/forum/#!forum/openresty 很快就有人回应了。原来是我没有在http{} 配置块内添加resty.core依赖： 

   init_by_lua_block {

        require "resty.core"

    }

其实参考文档内有说明依赖resty.core，且原文demo中也有配置init_by_lua_block……

怪自己太粗心，原文文档都没仔细阅读。