From 8a21ee2028b5f11fe0b9148078b49e4000937202 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jakob@driver.xyz>
Date: Tue, 11 Sep 2018 13:35:03 -0700
Subject: Rearchitect reporting stack to mixin-based structure

---
 src/main/scala/xyz/driver/core/app/DriverApp.scala |  3 +-
 src/main/scala/xyz/driver/core/app/init.scala      |  9 +++--
 .../scala/xyz/driver/core/init/AkkaBootable.scala  |  7 +++-
 .../scala/xyz/driver/core/init/CloudServices.scala | 28 +++++++------
 .../driver/core/reporting/GoogleMdcLogger.scala    | 14 +++++++
 .../xyz/driver/core/reporting/GoogleReporter.scala | 17 ++++----
 .../xyz/driver/core/reporting/NoReporter.scala     |  8 ++++
 .../driver/core/reporting/NoTraceReporter.scala    |  8 ++--
 .../scala/xyz/driver/core/reporting/Reporter.scala | 46 +++++++++++-----------
 .../driver/core/reporting/ScalaLoggerLike.scala    | 32 ---------------
 .../driver/core/reporting/ScalaLoggingCompat.scala | 36 +++++++++++++++++
 .../xyz/driver/core/reporting/SpanContext.scala    |  4 +-
 12 files changed, 123 insertions(+), 89 deletions(-)
 create mode 100644 src/main/scala/xyz/driver/core/reporting/GoogleMdcLogger.scala
 create mode 100644 src/main/scala/xyz/driver/core/reporting/NoReporter.scala
 delete mode 100644 src/main/scala/xyz/driver/core/reporting/ScalaLoggerLike.scala
 create mode 100644 src/main/scala/xyz/driver/core/reporting/ScalaLoggingCompat.scala

diff --git a/src/main/scala/xyz/driver/core/app/DriverApp.scala b/src/main/scala/xyz/driver/core/app/DriverApp.scala
index 50e471c..03da72b 100644
--- a/src/main/scala/xyz/driver/core/app/DriverApp.scala
+++ b/src/main/scala/xyz/driver/core/app/DriverApp.scala
@@ -91,8 +91,7 @@ class DriverApp(
       def route: Route = versionRt ~ healthRoute
     }
     val combinedRoute =
-      Route.seal(
-        modules.map(_.route).foldLeft(basicRoutes.routeWithDefaults)(_ ~ _) ~ swaggerRoute.route ~ defaultOptionsRoute)
+      Route.seal(modules.map(_.route).foldLeft(basicRoutes.routeWithDefaults)(_ ~ _) ~ swaggerRoute.route)
     (extractHost & extractClientIP & trace(tracer) & handleRejections(authenticationRejectionHandler)) {
       case (origin, ip) =>
         ctx =>
diff --git a/src/main/scala/xyz/driver/core/app/init.scala b/src/main/scala/xyz/driver/core/app/init.scala
index 767fd0b..bb7a798 100644
--- a/src/main/scala/xyz/driver/core/app/init.scala
+++ b/src/main/scala/xyz/driver/core/app/init.scala
@@ -10,7 +10,7 @@ import com.typesafe.config.{Config, ConfigFactory}
 import com.typesafe.scalalogging.Logger
 import org.slf4j.LoggerFactory
 import xyz.driver.core.logging.MdcExecutionContext
-import xyz.driver.core.reporting.{NoTraceReporter, ScalaLoggerLike}
+import xyz.driver.core.reporting.{ScalaLoggingCompat, NoTraceReporter}
 import xyz.driver.core.time.provider.TimeProvider
 import xyz.driver.tracing.{GoogleTracer, NoTracer, Tracer}
 
@@ -26,7 +26,7 @@ object init {
     val gitHeadCommit: scala.Option[String]
   }
 
-  case class ApplicationContext(config: Config, clock: Clock, reporter: ScalaLoggerLike) {
+  case class ApplicationContext(config: Config, clock: Clock, reporter: ScalaLoggingCompat) {
     val time: TimeProvider = clock
   }
 
@@ -90,7 +90,10 @@ object init {
     ApplicationContext(
       config = getEnvironmentSpecificConfig(),
       clock = Clock.systemUTC(),
-      new NoTraceReporter(Logger(LoggerFactory.getLogger(classOf[DriverApp]))))
+      new NoTraceReporter with ScalaLoggingCompat {
+        val logger = Logger(LoggerFactory.getLogger(classOf[DriverApp]))
+      }
+    )
 
   def createDefaultApplication(
       modules: Seq[Module],
diff --git a/src/main/scala/xyz/driver/core/init/AkkaBootable.scala b/src/main/scala/xyz/driver/core/init/AkkaBootable.scala
index 5e0b36c..df6611e 100644
--- a/src/main/scala/xyz/driver/core/init/AkkaBootable.scala
+++ b/src/main/scala/xyz/driver/core/init/AkkaBootable.scala
@@ -14,7 +14,7 @@ import com.typesafe.config.Config
 import kamon.Kamon
 import kamon.statsd.StatsDReporter
 import kamon.system.SystemMetrics
-import xyz.driver.core.reporting.{NoTraceReporter, Reporter, ScalaLoggerLike, SpanContext}
+import xyz.driver.core.reporting.{NoTraceReporter, Reporter, ScalaLoggingCompat, SpanContext}
 import xyz.driver.core.rest.HttpRestServiceTransport
 
 import scala.concurrent.duration._
@@ -119,7 +119,10 @@ trait AkkaBootable {
     *
     * @group utilities
     */
-  def reporter: Reporter with ScalaLoggerLike = new NoTraceReporter(ScalaLoggerLike.defaultScalaLogger(json = false))
+  def reporter: Reporter with ScalaLoggingCompat =
+    new Reporter with NoTraceReporter with ScalaLoggingCompat {
+      val logger = ScalaLoggingCompat.defaultScalaLogger(json = false)
+    }
 
   /** Top-level application configuration.
     *
diff --git a/src/main/scala/xyz/driver/core/init/CloudServices.scala b/src/main/scala/xyz/driver/core/init/CloudServices.scala
index 31faf4c..a6a477a 100644
--- a/src/main/scala/xyz/driver/core/init/CloudServices.scala
+++ b/src/main/scala/xyz/driver/core/init/CloudServices.scala
@@ -3,14 +3,12 @@ package init
 
 import java.nio.file.Paths
 
-import xyz.driver.core.messaging.{GoogleBus, QueueBus, StreamBus}
+import xyz.driver.core.messaging.{CreateOnDemand, GoogleBus, QueueBus, StreamBus}
 import xyz.driver.core.reporting._
-import xyz.driver.core.reporting.ScalaLoggerLike.defaultScalaLogger
 import xyz.driver.core.rest.{DnsDiscovery, ServiceDescriptor}
 import xyz.driver.core.storage.{BlobStorage, FileSystemBlobStorage, GcsBlobStorage}
 
 import scala.collection.JavaConverters._
-import scala.concurrent.ExecutionContext
 
 /** Mixin trait that provides essential cloud utilities. */
 trait CloudServices extends AkkaBootable { self =>
@@ -21,9 +19,8 @@ trait CloudServices extends AkkaBootable { self =>
   def platform: Platform = Platform.current
 
   /** Service discovery for the current platform.
-    *
     */
-  private lazy val discovery = {
+  private lazy val discovery: DnsDiscovery = {
     def getOverrides(): Map[String, String] = {
       val block = config.getObject("services.dev-overrides").unwrapped().asScala
       for ((key, value) <- block) yield {
@@ -33,7 +30,9 @@ trait CloudServices extends AkkaBootable { self =>
     }.toMap
     val overrides = platform match {
       case Platform.Dev => getOverrides()
-      case _            => Map.empty[String, String] // TODO we may want to provide a way to override deployed services as well
+      // TODO: currently, deployed services must be configured via Kubernetes DNS resolver. Maybe we may want to
+      // provide a way to override deployed services as well.
+      case _ => Map.empty[String, String]
     }
     new DnsDiscovery(clientTransport, overrides)
   }
@@ -47,13 +46,17 @@ trait CloudServices extends AkkaBootable { self =>
    * A potential fix would be to make the log format independent of the platform, and always log
    * as JSON for example.
    */
-  override lazy val reporter: Reporter with ScalaLoggerLike = {
+  override lazy val reporter: Reporter with ScalaLoggingCompat = {
     Console.println("determining platform") // scalastyle:ignore
     val r = platform match {
       case p @ Platform.GoogleCloud(_, _) =>
-        new GoogleReporter(p.credentials, p.namespace, defaultScalaLogger(true))
+        new GoogleReporter(p.credentials, p.namespace) with ScalaLoggingCompat with GoogleMdcLogger {
+          val logger = ScalaLoggingCompat.defaultScalaLogger(true)
+        }
       case Platform.Dev =>
-        new NoTraceReporter(defaultScalaLogger(false))
+        new NoTraceReporter with ScalaLoggingCompat {
+          val logger = ScalaLoggingCompat.defaultScalaLogger(false)
+        }
     }
     r.info(s"application started on platform '${platform}'")(SpanContext.fresh())
     r
@@ -78,11 +81,10 @@ trait CloudServices extends AkkaBootable { self =>
     * @group utilities
     */
   def messageBus: StreamBus = platform match {
-    case Platform.GoogleCloud(keyfile, namespace) => GoogleBus.fromKeyfile(keyfile, namespace)
+    case p @ Platform.GoogleCloud(_, namespace) =>
+      new GoogleBus(p.credentials, namespace) with StreamBus with CreateOnDemand
     case Platform.Dev =>
-      new QueueBus()(self.system) with StreamBus {
-        override def executionContext: ExecutionContext = self.executionContext
-      }
+      new QueueBus()(self.system) with StreamBus
   }
 
 }
diff --git a/src/main/scala/xyz/driver/core/reporting/GoogleMdcLogger.scala b/src/main/scala/xyz/driver/core/reporting/GoogleMdcLogger.scala
new file mode 100644
index 0000000..f5c41cf
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/reporting/GoogleMdcLogger.scala
@@ -0,0 +1,14 @@
+package xyz.driver.core
+package reporting
+
+import org.slf4j.MDC
+
+trait GoogleMdcLogger extends Reporter { self: GoogleReporter =>
+
+  abstract override def log(severity: Reporter.Severity, message: String, reason: Option[Throwable])(
+      implicit ctx: SpanContext): Unit = {
+    MDC.put("trace", s"projects/${credentials.getProjectId}/traces/${ctx.traceId}")
+    super.log(severity, message, reason)
+  }
+
+}
diff --git a/src/main/scala/xyz/driver/core/reporting/GoogleReporter.scala b/src/main/scala/xyz/driver/core/reporting/GoogleReporter.scala
index d4d20a4..14c4954 100644
--- a/src/main/scala/xyz/driver/core/reporting/GoogleReporter.scala
+++ b/src/main/scala/xyz/driver/core/reporting/GoogleReporter.scala
@@ -1,5 +1,6 @@
 package xyz.driver.core
 package reporting
+
 import java.security.Signature
 import java.time.Instant
 import java.util
@@ -9,8 +10,6 @@ import akka.stream.scaladsl.{Flow, RestartSink, Sink, Source, SourceQueueWithCom
 import akka.stream.{Materializer, OverflowStrategy}
 import com.google.auth.oauth2.ServiceAccountCredentials
 import com.softwaremill.sttp._
-import com.typesafe.scalalogging.Logger
-import org.slf4j.MDC
 import spray.json.DerivedJsonProtocol._
 import spray.json._
 import xyz.driver.core.reporting.Reporter.CausalRelation
@@ -18,22 +17,21 @@ import xyz.driver.core.reporting.Reporter.CausalRelation
 import scala.async.Async._
 import scala.concurrent.duration._
 import scala.concurrent.{ExecutionContext, Future}
-import scala.util.{Failure, Random, Success, Try}
 import scala.util.control.NonFatal
+import scala.util.{Failure, Random, Success, Try}
 
 /** A reporter that collects traces and submits them to
   * [[https://cloud.google.com/trace/docs/reference/v2/rest/ Google's Stackdriver Trace API]].
   */
 class GoogleReporter(
-    credentials: ServiceAccountCredentials,
+    val credentials: ServiceAccountCredentials,
     namespace: String,
-    val logger: Logger,
     buffer: Int = GoogleReporter.DefaultBufferSize,
     interval: FiniteDuration = GoogleReporter.DefaultInterval)(
     implicit client: SttpBackend[Future, _],
     mat: Materializer,
     ec: ExecutionContext
-) extends Reporter with ScalaLoggerLike {
+) extends Reporter {
   import GoogleReporter._
 
   private val getToken: () => Future[String] = Refresh.every(55.minutes) {
@@ -156,10 +154,9 @@ class GoogleReporter(
   }
 
   override def log(severity: Reporter.Severity, message: String, reason: Option[Throwable])(
-      implicit ctx: SpanContext): Unit = {
-    MDC.put("trace", s"projects/${credentials.getProjectId}/traces/${ctx.traceId}")
-    super.log(severity, message, reason)
-  }
+      implicit ctx: SpanContext): Unit =
+    sys.error("Submitting logs directly to GCP is " +
+      "currently not supported. Messages should go to stdout.") // TODO: attach logs to traces and submit them directly
 
 }
 
diff --git a/src/main/scala/xyz/driver/core/reporting/NoReporter.scala b/src/main/scala/xyz/driver/core/reporting/NoReporter.scala
new file mode 100644
index 0000000..c1c81f4
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/reporting/NoReporter.scala
@@ -0,0 +1,8 @@
+package xyz.driver.core
+package reporting
+
+trait NoReporter extends NoTraceReporter {
+  override def log(severity: Reporter.Severity, message: String, reason: Option[Throwable])(
+      implicit ctx: SpanContext): Unit = ()
+}
+object NoReporter extends NoReporter
diff --git a/src/main/scala/xyz/driver/core/reporting/NoTraceReporter.scala b/src/main/scala/xyz/driver/core/reporting/NoTraceReporter.scala
index 9179f42..b49cfda 100644
--- a/src/main/scala/xyz/driver/core/reporting/NoTraceReporter.scala
+++ b/src/main/scala/xyz/driver/core/reporting/NoTraceReporter.scala
@@ -1,18 +1,20 @@
 package xyz.driver.core
 package reporting
 
-import com.typesafe.scalalogging.Logger
-
 import scala.concurrent.Future
 
-class NoTraceReporter(val logger: Logger) extends Reporter with ScalaLoggerLike {
+/** A reporter mixin that does not emit traces. */
+trait NoTraceReporter extends Reporter {
+
   override def traceWithOptionalParent[A](
       name: String,
       tags: Map[String, String],
       parent: Option[(SpanContext, Reporter.CausalRelation)])(op: SpanContext => A): A = op(SpanContext.fresh())
+
   override def traceWithOptionalParentAsync[A](
       name: String,
       tags: Map[String, String],
       parent: Option[(SpanContext, Reporter.CausalRelation)])(op: SpanContext => Future[A]): Future[A] =
     op(SpanContext.fresh())
+
 }
diff --git a/src/main/scala/xyz/driver/core/reporting/Reporter.scala b/src/main/scala/xyz/driver/core/reporting/Reporter.scala
index 57e2310..469084c 100644
--- a/src/main/scala/xyz/driver/core/reporting/Reporter.scala
+++ b/src/main/scala/xyz/driver/core/reporting/Reporter.scala
@@ -1,8 +1,5 @@
-package xyz.driver.core.reporting
-
-import com.typesafe.scalalogging.Logger
-import org.slf4j.helpers.NOPLogger
-import xyz.driver.core.reporting.Reporter.{CausalRelation, Severity}
+package xyz.driver.core
+package reporting
 
 import scala.concurrent.Future
 
@@ -13,7 +10,7 @@ import scala.concurrent.Future
   * that led to a particular message. In synchronous systems, execution contexts can easily be determined by an
   * external observer, and, as such, do not need to be propagated explicitly to sub-components (e.g. a stack trace on
   * the JVM shows all relevant information). In asynchronous systems and especially distributed systems however,
-  * execution contexts are not easily determined by an external observer and hence need to be explcictly passed across
+  * execution contexts are not easily determined by an external observer and hence need to be explicitly passed across
   * service boundaries.
   *
   * This reporter provides tracing and logging utilities that explicitly require references to execution contexts
@@ -44,14 +41,15 @@ import scala.concurrent.Future
   * }
   * }}}
   *
-  * Note that computing traces may be a more expensive operation than traditional logging frameworks provide (in terms
-  * of memory and processing). It should be used in interesting and actionable code paths.
+  * '''Note that computing traces may be a more expensive operation than traditional logging frameworks provide (in terms
+  * of memory and processing). It should be used in interesting and actionable code paths.'''
   *
   * @define rootWarning Note: the idea of the reporting framework is to pass along references to traces as
   *                     implicit parameters. This method should only be used for top-level traces when no parent
   *                     traces are available.
   */
 trait Reporter {
+  import Reporter._
 
   def traceWithOptionalParent[A](
       name: String,
@@ -66,7 +64,7 @@ trait Reporter {
     *
     * $rootWarning
     */
-  def traceRoot[A](name: String, tags: Map[String, String] = Map.empty)(op: SpanContext => A): A =
+  final def traceRoot[A](name: String, tags: Map[String, String] = Map.empty)(op: SpanContext => A): A =
     traceWithOptionalParent(
       name,
       tags,
@@ -79,7 +77,8 @@ trait Reporter {
     *
     * @see traceRoot
     */
-  def traceRootAsync[A](name: String, tags: Map[String, String] = Map.empty)(op: SpanContext => Future[A]): Future[A] =
+  final def traceRootAsync[A](name: String, tags: Map[String, String] = Map.empty)(
+      op: SpanContext => Future[A]): Future[A] =
     traceWithOptionalParentAsync(
       name,
       tags,
@@ -102,8 +101,11 @@ trait Reporter {
     * @tparam A Return type of the operation.
     * @return The value of the child operation.
     */
-  def trace[A](name: String, tags: Map[String, String] = Map.empty, relation: CausalRelation = CausalRelation.Child)(
-      op: /* implicit (gotta wait for Scala 3) */ SpanContext => A)(implicit ctx: SpanContext): A =
+  final def trace[A](
+      name: String,
+      tags: Map[String, String] = Map.empty,
+      relation: CausalRelation = CausalRelation.Child)(op: /* implicit (gotta wait for Scala 3) */ SpanContext => A)(
+      implicit ctx: SpanContext): A =
     traceWithOptionalParent(
       name,
       tags,
@@ -117,7 +119,7 @@ trait Reporter {
     *
     * @see trace
     */
-  def traceAsync[A](
+  final def traceAsync[A](
       name: String,
       tags: Map[String, String] = Map.empty,
       relation: CausalRelation = CausalRelation.Child)(
@@ -132,31 +134,29 @@ trait Reporter {
   def log(severity: Severity, message: String, reason: Option[Throwable])(implicit ctx: SpanContext): Unit
 
   /** Log a debug message. */
-  def debug(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Debug, message, None)
-  def debug(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
+  final def debug(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Debug, message, None)
+  final def debug(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
     log(Severity.Debug, message, Some(reason))
 
   /** Log an informational message. */
-  def info(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Informational, message, None)
-  def info(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
+  final def info(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Informational, message, None)
+  final def info(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
     log(Severity.Informational, message, Some(reason))
 
   /** Log a warning message. */
-  def warn(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Warning, message, None)
-  def warn(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
+  final def warn(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Warning, message, None)
+  final def warn(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
     log(Severity.Warning, message, Some(reason))
 
   /** Log an error message. */
-  def error(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Error, message, None)
-  def error(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
+  final def error(message: String)(implicit ctx: SpanContext): Unit = log(Severity.Error, message, None)
+  final def error(message: String, reason: Throwable)(implicit ctx: SpanContext): Unit =
     log(Severity.Error, message, Some(reason))
 
 }
 
 object Reporter {
 
-  val NoReporter: Reporter = new NoTraceReporter(Logger.apply(NOPLogger.NOP_LOGGER))
-
   /** A relation in cause.
     *
     * Corresponds to
diff --git a/src/main/scala/xyz/driver/core/reporting/ScalaLoggerLike.scala b/src/main/scala/xyz/driver/core/reporting/ScalaLoggerLike.scala
deleted file mode 100644
index eda81fb..0000000
--- a/src/main/scala/xyz/driver/core/reporting/ScalaLoggerLike.scala
+++ /dev/null
@@ -1,32 +0,0 @@
-package xyz.driver.core.reporting
-import com.typesafe.scalalogging.Logger
-
-trait ScalaLoggerLike extends Reporter {
-
-  def logger: Logger
-
-  override def log(severity: Reporter.Severity, message: String, reason: Option[Throwable])(
-      implicit ctx: SpanContext): Unit = severity match {
-    case Reporter.Severity.Debug         => logger.debug(message, reason.orNull)
-    case Reporter.Severity.Informational => logger.info(message, reason.orNull)
-    case Reporter.Severity.Warning       => logger.warn(message, reason.orNull)
-    case Reporter.Severity.Error         => logger.error(message, reason.orNull)
-  }
-
-}
-
-object ScalaLoggerLike {
-  import scala.language.implicitConversions
-
-  def defaultScalaLogger(json: Boolean = false): Logger = {
-    if (json) {
-      System.setProperty("logback.configurationFile", "deployed-logback.xml")
-    } else {
-      System.setProperty("logback.configurationFile", "logback.xml")
-    }
-    Logger.apply("application")
-  }
-
-  implicit def toScalaLogger(reporter: ScalaLoggerLike): Logger = reporter.logger
-
-}
diff --git a/src/main/scala/xyz/driver/core/reporting/ScalaLoggingCompat.scala b/src/main/scala/xyz/driver/core/reporting/ScalaLoggingCompat.scala
new file mode 100644
index 0000000..0ff5574
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/reporting/ScalaLoggingCompat.scala
@@ -0,0 +1,36 @@
+package xyz.driver.core
+package reporting
+
+import com.typesafe.scalalogging.{Logger => ScalaLogger}
+
+/** Compatibility mixin for reporters, that enables implicit conversions to scala-logging loggers. */
+trait ScalaLoggingCompat extends Reporter {
+  import Reporter.Severity
+
+  def logger: ScalaLogger
+
+  override def log(severity: Severity, message: String, reason: Option[Throwable])(implicit ctx: SpanContext): Unit =
+    severity match {
+      case Severity.Debug         => logger.debug(message, reason.orNull)
+      case Severity.Informational => logger.info(message, reason.orNull)
+      case Severity.Warning       => logger.warn(message, reason.orNull)
+      case Severity.Error         => logger.error(message, reason.orNull)
+    }
+
+}
+
+object ScalaLoggingCompat {
+  import scala.language.implicitConversions
+
+  def defaultScalaLogger(json: Boolean = false): ScalaLogger = {
+    if (json) {
+      System.setProperty("logback.configurationFile", "deployed-logback.xml")
+    } else {
+      System.setProperty("logback.configurationFile", "logback.xml")
+    }
+    ScalaLogger.apply("application")
+  }
+
+  implicit def toScalaLogger(logger: ScalaLoggingCompat): ScalaLogger = logger.logger
+
+}
diff --git a/src/main/scala/xyz/driver/core/reporting/SpanContext.scala b/src/main/scala/xyz/driver/core/reporting/SpanContext.scala
index ecc2ba3..04a822d 100644
--- a/src/main/scala/xyz/driver/core/reporting/SpanContext.scala
+++ b/src/main/scala/xyz/driver/core/reporting/SpanContext.scala
@@ -1,10 +1,12 @@
 package xyz.driver.core
 package reporting
+
 import scala.util.Random
 
 case class SpanContext private[core] (traceId: String, spanId: String)
+
 object SpanContext {
-  def fresh() = SpanContext(
+  def fresh(): SpanContext = SpanContext(
     f"${Random.nextLong()}%016x${Random.nextLong()}%016x",
     f"${Random.nextLong()}%016x"
   )
-- 
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