metrics4-scala/nl.grons.metrics4.scala/DefaultInstrumented

DefaultInstrumented

trait DefaultInstrumented extends InstrumentedBuilder with CheckedBuilder

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.

trait CheckedBuilder

trait InstrumentedBuilder

trait BaseBuilder

class Object

trait Matchable

class Any

Value members

Inherited methods

Converts a code block to a com.codahale.metrics.health.HealthCheck and registers it.

Use it as follows:

object Application {
 // The application wide health check registry.
 val healthCheckRegistry = new com.codahale.metrics.health.HealthCheckRegistry()
}
trait Checked extends CheckedBuilder {
 val registry = Application.healthCheckRegistry
}

class ExampleWorker extends Checked {
 healthCheck("alive") { workerThreadIsActive() }
}

The code block must have a result of type Boolean, Try, Either, Future, com.codahale.metrics.health.HealthCheck.Result, or simply Unit.

A check result of true indicates healthy, false indicates unhealthy.
A check result of type Success indicates healthy, Failure indicates unhealthy. The embedded value (after applying .toString) or throwable is used as (un)healthy message.
A check result of type Future will have 3 seconds to execute (by default). The result of the execution will be treated as Success or Failure.
A check result of type Right indicates healthy, Left[Any] or Left[Throwable] indicates unhealthy. The embedded value (after applying .toString) or throwable is used as (un)healthy message.
If the check result is of type com.codahale.metrics.health.HealthCheck.Result, the result is passed unchanged.
A check result of type Unit indicates healthy.
If a checker throws an exception, the result is considered unhealthy with the throwable as unhealthy message.

It is also possible to override the health check base name. For example:

class ExampleWorker extends Checked {
 override lazy val metricBaseName = MetricName("Overridden.Base.Name")
 healthCheck("alive") { workerThreadIsActive() }
}

To change the timeout for Future execution, set an implicit duration:

class ExampleWorker extends Checked {
 implicit private val timeout = 10.seconds
 healthCheck("alive")(Future { workerThreadIsActive() })
}

NOTE: only one health check can be registered under a name (including the base name which is derived from the
class name by default). Any subsequent health check registrations will be ignored. This happens for example
when a class that defines a health check is instantiated multiple times. This metrics-core behavior might be
changed with https://github.com/dropwizard/metrics/issues/1245.

@param name the name of the health check
@param unhealthyMessage the unhealthy message for checkers that return `false`, defaults to `"Health check failed"`
@param checker the code block that does the health check

Inherited from: CheckedBuilder

The MetricBuilder that can be used for creating timers, counters, etc.

Inherited from: InstrumentedBuilder

Concrete fields

Inherited fields

The base name for all metrics created from this builder.

Inherited from: BaseBuilder

Inherited from: InstrumentedBuilder