handling multiple reading/writing requests; add rate for monitoring

So far, the process managing read/write requests and the monitoring worked as a while-True loop with the following steps:

1. check for read requests
2. check for write requests
3. expose monitoring metrics with prometheus
4. time sleep before restart

I converted the argument "timesleep" in "monitinterval", so now it described after how many seconds the process should expose again the prometheus metrics The new loop is like this:

1. check for read requests
2. check for write requests
3. check if current_time-previous_monitoring_time > monitoring_interval
4. if yes, expose monitoring metrics with prometheus; otherwise continue (back to step 1)