CalculateRates calculates the moving average rates per service.

NewMetricsClient returns a new client and starts collecting metrics.

NginxMetricsClient holds some state about the clients.

RateKey is the key for aggregated rates, which are averaged across all pods.

TotalKey is the indexing of totals from the nginx traffic stats, which vary per pod.

UpstreamMetric captures nginx metrics referring to upstreams.