Metrics
![](https://scalatra.github.io/scalatra-docbuild/images/glyphicons/glyphicons_023_cogwheels.png)
Scalatra supports metrics via the metrics and metrics-scala projects.
Setup
In order to make use of this functionality, add scalatra-metrics
to your build.sbt
:
"org.scalatra" %% "scalatra-metrics" % "2.7.0"
and mix in the MetricsBootstrap trait into ScalatraBootstrap:
class ScalatraBootstrap extends LifeCycle with MetricsBootstrap {
override def init(context: ServletContext) =
{
// ...
}
}
Mixing in MetricsBootstrap will provide a default instance of both a MetricRegistry and a HealthCheckRegistry to your application. You can also choose to override one or both if the defaults don’t suit your purpose.
class ScalatraBootstrap extends LifeCycle with MetricsBootstrap {
override val metricRegistry = ???
override val healthCheckRegistry = ???
override def init(context: ServletContext) =
{
}
}
Metrics Servlets
Convenience methods to mount the metrics servlets at a specified path from the init method are provided in MetricsSupportExtensions
.
import org.scalatra.metrics.MetricsSupportExtensions._
class ScalatraBootstrap extends LifeCycle with MetricsBootstrap {
override def init(context: ServletContext) =
{
context.mountMetricsAdminServlet("/metrics-admin")
context.mountHealthCheckServlet("/health")
context.mountMetricsServlet("/metrics")
context.mountThreadDumpServlet("/thread-dump")
context.installInstrumentedFilter("/test/*")
}
}
Details for what each servlet does are provided in the Metrics Servlets Documentation
Metrics Filter
A convenience method is also provided to mount a servlet filter to aggregate response code counts and timings. The parameter passed will specify where to apply the filter. To apply it globally, use /*
class ScalatraBootstrap extends LifeCycle with MetricsBootstrap {
override def init(context: ServletContext) =
{
context.installInstrumentedFilter("/test/*")
}
}
Measuring
In order to record metrics in your servlets, mix in the MetricsSupport
trait and call the provided methods:
class TestServlet extends ScalatraServlet with MetricsSupport {
get("/") {
timer("timer") {
// Code that's timed by a timer named "timer"
}
// Increments a counter called "counter"
counter("counter") += 1
// Increments a histogram called "histogram"
histogram("histogram") += 1
// Sets a gauge called "gauge"
gauge("gauge") {
"gauge"
}
// Sets a meter named "meter"
meter("meter").mark(1)
}
}
Health Checks
In order to make use of health checks, mix in the HealthChecksSupport
trait and define your health
checks:
class TestServlet extends ScalatraServlet with HealthChecksSupport {
get("/") {
healthCheck("basic") {
true
}
healthCheck("withMessage", unhealthyMessage = "DEADBEEF") {
true
}
}
}
Advanced
In addition to the provided convenience methods, the full metrics-core
, metrics-servlet
, metrics-servlets
, and metrics-scala
libraries are available for import. The default registries are exposed as implicit val
s, and so can be accessed directly if needed.