limit traffic based on rolling-counter/sliding-window using ngx.shared.DICT about lua-resty-limit-traffic

[agentzh]

Well, ngx_http_lua already supports the init parameter of incr, and we can utilize it here in this library.

I don't want this library to depend on a new 3rd-party nginx C module. But you are free to do whatever new feature experiments yourself :)

[alonbg]

@agentzh, sure, I would prefer not to reinvent stuff :)
But everything (logic under limit_req.incoming() as I described), preferably, should take place within a ngx_shmtx_lock section.
For sliding window I do need the queue. Did you mean adding this functionality to shared_dict list api ?

[agentzh]

@alonbg the standard lua_shared_dict implementation in ngx_http_lua_module already supports lists (or queues). Check it out to see if it fits your needs.

[alonbg]

@agentzh, for my case, using lua_shared_dict lists might cause a race condition. Well, I can use the lua lock API but there would be an overhead if used for every request. Actually, better to think of it as a special kind of rolling incr, which is initialized with window, resolution and an optional max value (being the max sum of all queue elements ). The data structure behind is the queue and the timestamp. I think I'll go forward with the c-api separate modul option and if it's generic enough you could consider it later on for ngx_http_lua_model.
Thanks