#20 Write stats collecting mechanism

A solution to a fast request counter implementation can use semaphores : When a worker starts handling a request it increment a sempahore. Meanwhile, a counter process (pool_handler or stats collection child) will attempt to decrease (fast enough) the semaphore with WNOHANG. If the decrement semop do not fail, a counter can be incremented. Note : the 10/5/1 min counters implies to store all requests timestamps ?? Maybe we can associate a timestamp with a request count ? <code>=> if 100 req/s stores {time(NULL), 100} and not time_t [100] = {time(NULL), time(NULL), etc.}</code>