Reset registry on module load to make sure that we can use hot reload…

… of play framework

app/com/github/stijndehaes/playprometheusfilters/PrometheusModule.scala

@@ -6,6 +6,7 @@ import io.prometheus.client.CollectorRegistry
 class PrometheusModule extends AbstractModule {
 
   override def configure(): Unit = {
+    CollectorRegistry.defaultRegistry.clear()
     bind(classOf[CollectorRegistry]).toInstance(CollectorRegistry.defaultRegistry)
   }
 }

app/com/github/stijndehaes/playprometheusfilters/controllers/PrometheusController.scala

@@ -5,12 +5,16 @@ import com.github.stijndehaes.playprometheusfilters.utils.WriterAdapter
 import com.google.inject.Inject
 import io.prometheus.client.CollectorRegistry
 import io.prometheus.client.exporter.common.TextFormat
+import org.slf4j.LoggerFactory
 import play.api.http.HttpEntity
 import play.api.mvc._
 
 class PrometheusController @Inject()(registry: CollectorRegistry) extends Controller {
 
+  private val logger = LoggerFactory.getLogger(classOf[PrometheusController])
+
   def getMetrics = Action {
+    logger.trace("Metrics call received")
     val samples = new StringBuilder()
     val writer = new WriterAdapter(samples)
     TextFormat.write004(writer, registry.metricFamilySamples())

app/com/github/stijndehaes/playprometheusfilters/filters/StatusAndRouteLatencyFilter.scala

@@ -1,13 +1,14 @@
 package com.github.stijndehaes.playprometheusfilters.filters
 
 import akka.stream.Materializer
-import com.google.inject.Inject
+import com.google.inject.{Inject, Singleton}
 import io.prometheus.client.{Collector, CollectorRegistry, Histogram}
 import play.api.mvc.{Filter, RequestHeader, Result}
 import play.api.routing.Router.Tags
 
 import scala.concurrent.{ExecutionContext, Future}
 
+@Singleton
 class StatusAndRouteLatencyFilter @Inject()(registry: CollectorRegistry) (implicit val mat: Materializer, ec: ExecutionContext) extends Filter {
 
   private[filters] val requestLatency = Histogram.build