Counter is a cumulative metric that represents a single numerical value that only ever goes up.
Counter builder.
Collect trait implmentation for Counter.
Gauge is a metric that represents a single numerical value that can arbitrarily go up and down.
Gauge builder.
Collect trait implmentation for Gauge.
Histogram samples observations (usually things like request durations or response sizes) and
counts them in configurable buckets.
It also provides a sum of all observed values.
Histogram builder.
Collect trait implmentation for Histogram.
Common builder for various metrics.
Process metrics collector.
Summary samples observations (usually things like request durations and response sizes).
Summary builder.
Collect trait implmentation for Summary.