= core: put the ModuleLoader back in place for auto-starting modules.

1 files changed, 109 insertions, 0 deletions

diff --git a/kamon-core/src/main/scala/kamon/ModuleLoader.scala b/kamon-core/src/main/scala/kamon/ModuleLoader.scala
new file mode 100644
index 00000000..84d93943
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/ModuleLoader.scala
@@ -0,0 +1,109 @@
+package kamon
+
+import _root_.akka.actor
+import _root_.akka.actor._
+import _root_.akka.event.Logging
+import org.aspectj.lang.ProceedingJoinPoint
+import org.aspectj.lang.annotation.{Around, Pointcut, Aspect}
+
+
+private[kamon] object ModuleLoader extends ExtensionId[ModuleLoaderExtension] with ExtensionIdProvider {
+  def lookup(): ExtensionId[_ <: actor.Extension] = ModuleLoader
+  def createExtension(system: ExtendedActorSystem): ModuleLoaderExtension = new ModuleLoaderExtension(system)
+}
+
+private[kamon] class ModuleLoaderExtension(system: ExtendedActorSystem) extends Kamon.Extension {
+  val log = Logging(system, "ModuleLoader")
+  val settings = ModuleLoaderSettings(system)
+
+
+  if (settings.modulesRequiringAspectJ.nonEmpty && !isAspectJPresent && settings.showAspectJMissingWarning)
+    logAspectJWeaverMissing(settings.modulesRequiringAspectJ)
+
+  // Force initialization of all modules marked with auto-start.
+  settings.availableModules.filter(_.autoStart).foreach { module ⇒
+    if (module.extensionClass == "none")
+      log.debug("Ignoring auto start of the [{}] module with no extension class.")
+    else
+      system.dynamicAccess.getObjectFor[ExtensionId[Kamon.Extension]](module.extensionClass).map { moduleID ⇒
+        log.debug("Auto starting the [{}] module.", module.name)
+        moduleID.get(system)
+
+      } recover {
+        case th: Throwable ⇒ log.error(th, "Failed to auto start the [{}] module.", module.name)
+      }
+
+  }
+
+  // When AspectJ is present the kamon.supervisor.AspectJPresent aspect will make this return true.
+  def isAspectJPresent: Boolean = false
+
+  def logAspectJWeaverMissing(modulesRequiringAspectJ: List[AvailableModuleInfo]): Unit = {
+    val moduleNames = modulesRequiringAspectJ.map(_.name).mkString(", ")
+    val weaverMissingMessage =
+      """
+        |
+        |  ___                           _      ___   _    _                                 ___  ___ _            _
+        | / _ \                         | |    |_  | | |  | |                                |  \/  |(_)          (_)
+        |/ /_\ \ ___  _ __    ___   ___ | |_     | | | |  | |  ___   __ _ __   __ ___  _ __  | .  . | _  ___  ___  _  _ __    __ _
+        ||  _  |/ __|| '_ \  / _ \ / __|| __|    | | | |/\| | / _ \ / _` |\ \ / // _ \| '__| | |\/| || |/ __|/ __|| || '_ \  / _` |
+        || | | |\__ \| |_) ||  __/| (__ | |_ /\__/ / \  /\  /|  __/| (_| | \ V /|  __/| |    | |  | || |\__ \\__ \| || | | || (_| |
+        |\_| |_/|___/| .__/  \___| \___| \__|\____/   \/  \/  \___| \__,_|  \_/  \___||_|    \_|  |_/|_||___/|___/|_||_| |_| \__, |
+        |            | |                                                                                                      __/ |
+        |            |_|                                                                                                     |___/
+        |
+        | It seems like your application was not started with the -javaagent:/path-to-aspectj-weaver.jar option but Kamon detected
+        | the following modules which require AspecJ to work properly:
+        |
+      """.stripMargin + moduleNames +
+        """
+          |
+          | If you need help on setting up the aspectj weaver go to http://kamon.io/introduction/get-started/ for more info. On the
+          | other hand, if you are sure that you do not need or do not want to use the weaver then you can disable this error message
+          | by changing the kamon.show-aspectj-missing-warning setting in your configuration file.
+          |
+        """.stripMargin
+
+    log.error(weaverMissingMessage)
+  }
+}
+
+private[kamon] case class AvailableModuleInfo(name: String, extensionClass: String, requiresAspectJ: Boolean, autoStart: Boolean)
+private[kamon] case class ModuleLoaderSettings(showAspectJMissingWarning: Boolean, availableModules: List[AvailableModuleInfo]) {
+  val modulesRequiringAspectJ = availableModules.filter(_.requiresAspectJ)
+}
+
+private[kamon] object ModuleLoaderSettings {
+
+  def apply(system: ActorSystem): ModuleLoaderSettings = {
+    import kamon.util.ConfigTools.Syntax
+
+    val config = system.settings.config.getConfig("kamon.modules")
+    val showAspectJMissingWarning = system.settings.config.getBoolean("kamon.show-aspectj-missing-warning")
+
+    val modules = config.firstLevelKeys
+    val availableModules = modules.map { moduleName ⇒
+      val moduleConfig = config.getConfig(moduleName)
+
+      AvailableModuleInfo(
+        moduleName,
+        moduleConfig.getString("extension-id"),
+        moduleConfig.getBoolean("requires-aspectj"),
+        moduleConfig.getBoolean("auto-start"))
+
+    } toList
+
+    ModuleLoaderSettings(showAspectJMissingWarning, availableModules)
+  }
+}
+
+@Aspect
+private[kamon] class AspectJPresent {
+
+  @Pointcut("execution(* kamon.ModuleLoaderExtension.isAspectJPresent())")
+  def isAspectJPresentAtModuleSupervisor(): Unit = {}
+
+  @Around("isAspectJPresentAtModuleSupervisor()")
+  def aroundIsAspectJPresentAtModuleSupervisor(pjp: ProceedingJoinPoint): Boolean = true
+
+}