Openresty 根据 IP 限流

Question

配置：

http {
    lua_shared_dict my_limit_req_store 100m;

    server {
        location / {
            access_by_lua_block {

                local limit_req = require "resty.limit.req"

                -- limit the requests under 200 req/sec with a burst of 100 req/sec,
                -- that is, we delay requests under 300 req/sec and above 200
                -- req/sec, and reject any requests exceeding 300 req/sec.
                -- 200req/sec 以下不限流，300req/sec 拒绝，200~300req/sec 延迟

                local lim, err = limit_req.new("my_limit_req_store", 200, 100)
                if not lim then
                    ngx.log(ngx.ERR,
                            "failed to instantiate a resty.limit.req object: ", err)
                    return ngx.exit(500)
                end

                -- the following call must be per-request.
                -- here we use the remote (IP) address as the limiting key
                -- 限制条件为 ip
                local key = ngx.var.binary_remote_addr
                -- 300 以上，err 为 rejected,200~300 err 为超过 200 的额外请求数，delay 为延迟时间
                local delay, err = lim:incoming(key, true)
                if not delay then
                    if err == "rejected" then
                        return ngx.exit(503)
                    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. for example, number 31
                    -- means the current request rate is at 231 req/sec for the
                    -- specified key.
                    local excess = err

                    -- the request exceeding the 200 req/sec but below 300 req/sec,
                    -- so we intentionally delay it here a bit to conform to the
                    -- 200 req/sec rate.
                    ngx.sleep(delay)
                end
            }

            # content handler goes here. if it is content_by_lua, then you can
            # merge the Lua code above in access_by_lua into your content_by_lua's
            # Lua handler to save a little bit of CPU time.
        }
    }
}