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Dropwizards Metrics

hint: metrics.dropwizard.io v4

Main concepts here:

  • Metric: a Metric is contained in the MetricRegistry and it has an unique name (i.e. a dotted-name string) used to retrieve the Metric from the MetricRegistry.

  • MetricRegistry: it is the container for all the metrics. Usually, there is one MetricRegistry for each application.

  • Meters: a meter measures the rate of events over time (e.g., “requests per second”). A single meter includes mean rate and 1 5 15 moving averages.

    • Instance: metricRegistry.meter("the.meter.name")
    • Usage: meter.mark();

  • Gauges: a gauge is an instantaneous measurement of a value.

    • Register with: metricRegistry.register("the.gauge.name", theGauge);

  • Counters: a counter is a gauge for an AtomicLong. It is used to count, obviously.

    • Instance: metricRegistry.counter("the.counter.name")
    • Usage: counter.inc(); and/or counter.dec();

  • Histograms: a histogram measures the statistical distribution of values in a stream of data (e.g. the response times). It provides: minimum, maximum, mean, median, and percentiles (75th, 90th, 95th, 98th, 99th, and 99.9th).

    • Instance: metricRegistry.histogram("the.histogram.name")
    • Usage: histogram.update(aStreamValue);

  • Timers: a timer measures both the rate that a particular piece of code is called (like the a Meter) and the distribution of its duration (like a Histogram).

    • Instance: metricRegistry.time("the.timer.name")
    • Usage: context = timer.time(); and context.stop()