Switched back to using default registry cause it causes problems with…

… other metrics like Hikari metric.

In test clearing registry before each test. Had to change default to 'false' otherwise could not get test working when running all test. Disabling parallel test execution also did not help. No idea why.
Updated Readme.

README.md

@@ -114,7 +114,7 @@ You should be able to immediately get the metrics
 
 The [Prometheus Hotspot library](https://github.com/prometheus/client_java#included-collectors) provides some default collectors
 for garbage collection, memory pool, etc.
-Default these collectors are registered. This can be changed by setting the configuration property to `false`.
+Default these collectors are _not_ registered. This can be changed by setting the configuration property to `true`.
 
 ```
 play-prometheus-filters.register-default-hotspot-collectors = true

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

@@ -12,33 +12,15 @@ object PrometheusModule {
 class PrometheusModule extends Module {
   import PrometheusModule._
 
-  /**
-    * Registering default exporters. See [[DefaultExports.initialize()]]
-    *
-    * Not using DefaultExports.initialize since that makes it impossible to test.
-    * Guice guarantees this is only run once for an application.
-    */
-  def registerDefaultExporters(registry: CollectorRegistry): Unit = {
-    registry.register(new StandardExports)
-    registry.register(new MemoryPoolsExports)
-    registry.register(new BufferPoolsExports)
-    registry.register(new GarbageCollectorExports)
-    registry.register(new ThreadExports)
-    registry.register(new ClassLoadingExports)
-    registry.register(new VersionInfoExports)
-  }
-
   override def bindings(environment: Environment, configuration: Configuration): Seq[Binding[_]] = {
-    val registry = new CollectorRegistry(true)
-
     configuration.getOptional[Boolean](defaultExportsKey).foreach { enabled =>
       if (enabled) {
-        registerDefaultExporters(registry)
+        DefaultExports.initialize()
       }
     }
 
     Seq(
-      bind[CollectorRegistry].to(registry)
+      bind[CollectorRegistry].to(CollectorRegistry.defaultRegistry)
     )
   }
 }

conf/reference.conf

@@ -1,4 +1,4 @@
 play.modules.enabled += com.github.stijndehaes.playprometheusfilters.PrometheusModule
 
 # Registers some default collectors for jvm metrics. See DefaultExports class.
-play-prometheus-filters.register-default-hotspot-collectors = true
+play-prometheus-filters.register-default-hotspot-collectors = false

test/com/github/stijndehaes/playprometheusfilters/PrometheusModuleSpec.scala

@@ -1,15 +1,22 @@
 package com.github.stijndehaes.playprometheusfilters
 
 import io.prometheus.client.CollectorRegistry
-import org.scalatest.{MustMatchers, WordSpec}
+import org.scalatest.{BeforeAndAfter, MustMatchers, WordSpec}
 import play.api.inject.guice.GuiceApplicationBuilder
 
-class PrometheusModuleSpec extends WordSpec with MustMatchers {
+class PrometheusModuleSpec extends WordSpec with MustMatchers with BeforeAndAfter {
+
+  before {
+    // clearing registry before each test
+    CollectorRegistry.defaultRegistry.clear()
+  }
 
   "PrometheusModule" should {
     "register default exporters when enabled" in {
       // default enabled
-      val app = new GuiceApplicationBuilder().build()
+      val app = new GuiceApplicationBuilder()
+        .configure(PrometheusModule.defaultExportsKey -> true)
+        .build()
 
       val collector = app.injector.instanceOf[CollectorRegistry]
       collector.getExporterNames.size must be > 0