A new scala class for recording DropWizard Metrics artifacts as JSON with SLF4J Reporter

JsonSlf4jReporter.scala

package com.tormund

import java.util
import java.util.concurrent.TimeUnit

import com.codahale.metrics._
import com.typesafe.scalalogging.StrictLogging
import org.json4s.DefaultFormats

/**
  * an extension of the built-in SLF4J reporter to emit artifacts as JSON instead of regular string
  *
  * @param registry
  * @param name
  * @param filter
  * @param rateUnit
  * @param durationUnit
  */
class JsonSlf4jReporter(registry: MetricRegistry,
                        name: String,
                        filter: MetricFilter,
                        rateUnit: TimeUnit,
                        durationUnit: TimeUnit)
  extends ScheduledReporter(registry: MetricRegistry,
    name: String,
    filter: MetricFilter,
    rateUnit: TimeUnit,
    durationUnit: TimeUnit) with StrictLogging {

  case class TimerStats(name: String, count: Long, mean: Double, min: Double, max: Double)

  /**
    * emit the snapshots as JSON via SLF4J
    *
    * @param gauges
    * @param counters
    * @param histograms
    * @param meters
    * @param timers
    */
  override def report(gauges: util.SortedMap[String, Gauge[_]],
                      counters: util.SortedMap[String, Counter],
                      histograms: util.SortedMap[String, Histogram],
                      meters: util.SortedMap[String, Meter],
                      timers: util.SortedMap[String, Timer]) = {

    import org.json4s.jackson.Serialization._
    import collection.JavaConverters._

    implicit val formats = DefaultFormats

    // obviously this is not complete but you get the idea of what we're trying to do here 😊
    val stats = timers.asScala.map {
      case (k, t) => (k, TimerStats(k, t.getCount,
        convertDuration(t.getSnapshot.getMean),
        convertDuration(t.getSnapshot.getMin),
        convertDuration(t.getSnapshot.getMax)))
    }

    logger.info(s"${write(stats)}")
  }
}

object JsonSlf4jReporter {
  def apply(registry: MetricRegistry, name: String) = new JsonSlf4jReporter(registry, name, MetricFilter.ALL, TimeUnit.SECONDS, TimeUnit.MILLISECONDS)
}