We resume our discussion on the queue layer over object storage from the previous post. It is important for the Queue layer to understand resources usages. These resources usage metrics may apply to different queues, per queue or even as granular as per services. For example, we may have a queue that services a single consumer. It may have process that return different status codes. A simple metric may be to find out success rate in terms of the overall processing made. The success in this case is determined by the number of success status code generated over the processing. Since this kind of metric comes from individual messages, the queue may want to aggregate these metrics across all messages. This is best shown in a dashboard with drill downs to different services. 

  

It's important to note that metrics data is inherently time based. Although metrics can be spot measurements, cumulative over time or delta between time slices, they have an association with the time that they were measured.  Consequently, most metric data is stored in a time series database. Also, previous measurements can be summarized with statistics while the running measurements apply to only the current window of time. Therefore, some of these time-series databases can even be fix-sized. 

  

There are many different tools available to present such charts from data sources. Almost all such reporting mechanisms want to pull data for their charts. However, they cannot directly call the services to query their metrics because this may affect the functionality and performance of those services. Therefore, they do it in a passive manner by finding information from log trails and database states. Most services have logging configured and their logs are usually indexed in a time series database of their own. In our case we can utilize the objects to as time-series buckets that fill over. Consequently, the pull information can come from dedicated namespaces, buckets and objects in the object storage. 

boolean hasLessSetThanUnsetBits(int n)
{
    int set = 0;
    int unset = 0;
    while (n)
    {
        if (n & 0x1) {
             set++;
        } else { 
             unset++;
        }
        n = n >> 1;
    }
    return (set < unset);
}