eg.txt

        location /hello {
            content_by_lua_block {
                local lim = require "limit_conn"

                -- local key = ngx.var.binary_remote_addr
                local exceptions = ngx.worker.exceptions()

                local key = string.char(exceptions % 256) .. ngx.var.binary_remote_addr
                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 lim:is_committed() then
                    local ctx = ngx.ctx
                    ctx.limit_conn = lim
                    ctx.limit_conn_key = key
                    ctx.limit_conn_delay = delay
                end

                if delay >= 0.001 then
                    ngx.sleep(delay)
                end

                ngx.say("hello")
            }
       }