fallback to reference configuration when the application config fails to load, related to #564

Author: ivantopo

kamon-core-tests/src/test/scala/kamon/InitialConfigLoadingSpec.scala

@@ -0,0 +1,51 @@
+package kamon
+
+import java.io._
+import java.util.concurrent.TimeUnit
+
+import org.scalatest.{Matchers, WordSpec}
+import org.scalatest.concurrent.Eventually
+import org.scalatest.time.SpanSugar._
+
+import scala.util.{Failure, Success, Try}
+
+class InitialConfigLoadingSpec extends WordSpec with Matchers with Eventually {
+
+  "the initial config loading" should {
+    "fallback to using reference configuration only when application.conf files are malformed" in {
+      val process = Runtime.getRuntime.exec(createProcessWithConfig("kamon.KamonWithCustomConfig", "{This is a bad config}"))
+      val processOutputReader = new BufferedReader(new InputStreamReader(process.getInputStream()))
+
+      eventually(timeout(10 seconds)) {
+        val outputLine = processOutputReader.readLine()
+        outputLine shouldBe "All Good"
+      }
+
+      if(process.isAlive) {
+        process.destroyForcibly().waitFor(5, TimeUnit.SECONDS)
+      }
+    }
+  }
+
+  def createProcessWithConfig(mainClass: String, configContent: String): String = {
+    val tempConfigFile = File.createTempFile("bad-config", ".conf")
+    val writer = new BufferedWriter(new FileWriter(tempConfigFile))
+    writer.write(configContent)
+    writer.flush()
+    writer.close()
+
+    val configOptions = "-Dconfig.trace=loads -Dconfig.file=" + tempConfigFile.getAbsolutePath()
+    System.getProperty("java.home") + File.separator + "bin" + File.separator + "java " + configOptions +
+      " -cp " + System.getProperty("java.class.path") + " " + mainClass
+  }
+}
+
+object KamonWithCustomConfig extends App {
+  Try {
+    Kamon.counter("test").increment()
+  } match {
+    case Success(_) => println("All Good")
+    case Failure(_) => println("All Bad")
+  }
+
+}

kamon-core/src/main/scala/kamon/Kamon.scala

@@ -32,7 +32,7 @@ import scala.util.Try
 object Kamon extends MetricLookup with ReporterRegistry with Tracer {
   private val logger = LoggerFactory.getLogger("kamon.Kamon")
 
-  @volatile private var _config = ConfigFactory.load()
+  @volatile private var _config = loadInitialConfiguration()
   @volatile private var _environment = Environment.fromConfig(_config)
   @volatile private var _filters = Filters.fromConfig(_config)
 
@@ -187,6 +187,27 @@ object Kamon extends MetricLookup with ReporterRegistry with Tracer {
   private def schedulerPoolSize(config: Config): Int =
     config.getInt("kamon.scheduler-pool-size")
 
+  private def loadInitialConfiguration(): Config = {
+    Try {
+      ConfigFactory.load(ConfigFactory.load())
+
+    } recoverWith {
+      case t: Throwable =>
+        logger.warn("Failed to load the default configuration, attempting to load the reference configuration", t)
+
+        Try {
+          val referenceConfig = ConfigFactory.defaultReference()
+          logger.warn("Initializing with the default reference configuration, none of the user settings might be in effect", t)
+          referenceConfig
+        }
+
+    } recover {
+      case t: Throwable =>
+        logger.error("Failed to load the reference configuration, please check your reference.conf files for errors", t)
+        ConfigFactory.empty()
+    } get
+  }
+
 }
 
 trait OnReconfigureHook {