nl.grons.metrics4.scala

Provides a wrapper for by-name expressions with the intent that they can become eligible for implicit conversions and implicit resolution.

The mixin trait for creating a class which creates health checks.

A Scala facade class for DropwizardCounter.

A mixin trait for creating a class that publishes metrics and health checks to the "default" registries.

This follows the Dropwizard 1.0.0+ application convention of storing the metric registry to SharedMetricRegistries under the name "default". This was extended with storing the health check registry to SharedHealthCheckRegistries under the same name.

After mixing in this trait, metrics and health checks can be defined. For example:

class Example(db: Database) extends DefaultInstrumented {
 // Define a health check:
 healthCheck("alive") { workerThreadIsActive() }

 // Define a timer metric:
 private[this] val loading = metrics.timer("loading")

 // Use the timer metric:
 def loadStuff(): Seq[Row] = loading.time {
   db.fetchRows()
 }
}

See InstrumentedBuilder for instruction on overriding the metric base name or using hdrhistograms. See CheckedBuilder for instructions on overriding the timeout for scala.concurrent.Future executions.

A mixin trait to get a fresh empty health check registry every time.

See FreshRegistries for more information.

A mixin trait to get a fresh empty metric registry every time.

See FreshRegistries for more information.

A mixin trait to get a fresh empty metric and health check registry every time.

Often a singleton service class defines a gauge with a static name. However, during testing multiple instances are needed. Unfortunately the metrics registry doesn't allow registering a gauge under the same name twice. This is not a problem when a new registry is used for each instance.

The same is the case for health checks (since dropwizard-metrics 4.1).

Example

With the following gauge in class Example:

class Example(db: Database) extends nl.grons.metrics4.scala.DefaultInstrumented {
 // Define a gauge with a static name
 metrics.gauge("aGauge") { db.rowCount() }
}

This trait can be mixed in with any instance of Example:

 val example = new Example(db) with FreshRegistries

See also FreshMetricRegistry and FreshHealthCheckRegistry in case your class only extends InstrumentedBuilder or CheckedBuilder respectively.

A Scala facade class for DropwizardGauge.

Magnet for the checker. See http://spray.io/blog/2012-12-13-the-magnet-pattern/.

A Scala facade class for DropwizardHistogram.

Implicit conversions of Scala functions to Metric interfaces.

NOTE: no longer needed in Scala 2.12 and later.

The mixin trait for creating a class which is instrumented with metrics.

Use it as follows:

object Application {
 // The application wide metrics registry.
 val metricRegistry = new com.codahale.metrics.MetricRegistry()
}
trait Instrumented extends InstrumentedBuilder {
 val metricRegistry = Application.metricRegistry
}

class Example(db: Database) extends Instrumented {
 private[this] val loading = metrics.timer("loading")

 def loadStuff(): Seq[Row] = loading.time {
   db.fetchRows()
 }
}

As an alternative to your own Instrumented as above, it is possible to use DefaultInstrumented instead.

By default metric names are prefixed with the name of the current class. You can override this metric base name. For example:

class Example(db: Database) extends Instrumented {
 override lazy val metricBaseName = MetricName("Overridden.Base.Name")
 private[this] val loading = metrics.timer("loading")

 def loadStuff(): Seq[Row] = loading.time {
   db.fetchRows()
 }
}

If you want to use hdrhistograms, you can override the metric builder as follows:

trait Instrumented extends InstrumentedBuilder {
 override lazy protected val metricBuilder = new HdrMetricBuilder(metricBaseName, metricRegistry, false)
 val metricRegistry = Application.metricRegistry
}

See the the manual for more instructions on using hdrhistogram.

A Scala facade class for DropwizardMeter.

Example usage:

 class Example(val db: Db) extends Instrumented {
   private[this] val rowsLoadedMeter = metrics.meter("rowsLoaded")

   def load(id: Long): Seq[Row] = {
     val rows = db.load(id)
     rowsLoaded.mark(rows.size)
     rows
   }
 }

Builds and registers metrics.

The (base)name of a metric.

Constructed via the companion object, e.g. MetricName(getClass, "requests").

A gauge to which you can push new values.

Can only be constructed via MetricBuilder.pushGauge.

A gauge to which you can push new values. Values are forgotten after some time.

Can only be constructed via MetricBuilder.pushGaugeWithTimeout.

A Scala facade class for DropwizardTimer.

Features:

• measure the execution duration of a block of code with time
• measure the time until a future is completed with timeFuture
• add an execution duration measurement as a side effect to a partial function with timePF
• direct access to the underlying timer with update, timerContext, count, max, etc.

Example usage:

 class Example(val db: Db) extends Instrumented {
   private[this] val loadTimer = metrics.timer("load")

   def load(id: Long) = loadTimer.time {
     db.load(id)
   }
 }