[DISCUSS] How to set up limit-* plugin for user specific key from post body/cookie/arg/headers

[Lang Wang]

Hello all,


We used to use this code below [1] to deal with limit-* case (for example:
ratelimit for sending sms verifycode):

mobile stands for users' mobile phone no. from http post body.
But for other people maybe use `cookie`, `arg` or `mobile_phone` from body
instead.
So how can we avoid hard coding this key in the lua code?


1. lua code like:

location /verifycode {
    default_type 'application/json';

    #so you can to use set_by_lua from $mobile
    set $mobile '';

    access_by_lua_block {
        local request_method = ngx.var.request_method
        local args = nil
        if "GET" == request_method then
            local arg = ngx.req.get_uri_args()["mobile"] or 0
            ngx.var.mobile = arg
        elseif "POST" == request_method then
            cjson = require "cjson"
            local body = ngx.req.get_body_data()
            if body then
                -- parsing json body for  {mobile : 123, address: .... }
                local body = cjson.decode(body)
                local arg = body.mobile or 0
                ngx.var.mobile = arg
            end
        end

        local ratelimit = require "resty.redis.ratelimit"
        local lim, err = ratelimit.new("verifycode", "1r/m", 0, 0)

        if not lim then
            ngx.log(ngx.ERR,
                    "failed to instantiate a resty.redis.ratelimit
object: ", err)
            return ngx.exit(500)
        end

        local red = { host = "", port = 6379, timeout = 1, pass = "" }

        local key = ngx.var.mobile
        local delay, err = lim:incoming(key, red)
        if not delay then
            if err == "rejected" then
                return ngx.exit(429)
                -- cjson = require "cjson"
                -- ngx.say(cjson.encode({ code=1603, message = "Too
Many Requests", successful = true }))
            end
            ngx.log(ngx.ERR, "failed to limit req: ", err)
            return ngx.exit(500)
        end

        if delay >= 0.001 then
            -- the 2nd return value holds the number of excess requests
            -- per second for the specified key.
            local excess = err

            ngx.sleep(delay)
        end
    }
}




Thanks.