Tracing doodles

build.sbt

@@ -38,21 +38,24 @@ val catsEffectVersion = "3.2.9"
 val circeVersion = "0.14.1"
 val fs2Version = "3.2.2"
 val http4sVersion = "0.23.6"
+val natchezVersion = "0.1.5"
 
 lazy val root =
   project
     .in(file("."))
     .aggregate(
       core.js,
       core.jvm,
-      lambdaCloudFormationCustomResource.js,
-      lambdaCloudFormationCustomResource.jvm,
       lambda.js,
       lambda.jvm,
       lambdaEvents.js,
       lambdaEvents.jvm,
+      lambdaNatchez.js,
+      lambdaNatchez.jvm,
       lambdaApiGatewayProxyHttp4s.js,
-      lambdaApiGatewayProxyHttp4s.jvm
+      lambdaApiGatewayProxyHttp4s.jvm,
+      lambdaCloudFormationCustomResource.js,
+      lambdaCloudFormationCustomResource.jvm
     )
     .enablePlugins(NoPublishPlugin)
 
@@ -98,6 +101,17 @@ lazy val lambdaEvents = crossProject(JSPlatform, JVMPlatform)
     )
   )
 
+lazy val lambdaNatchez = crossProject(JSPlatform, JVMPlatform)
+  .crossType(CrossType.Pure)
+  .in(file("lambda-natchez"))
+  .settings(
+    name := "feral-lambda-natchez",
+    libraryDependencies ++= Seq(
+      "org.tpolecat" %%% "natchez-core" % natchezVersion
+    )
+  )
+  .dependsOn(lambda, lambdaEvents)
+
 lazy val lambdaApiGatewayProxyHttp4s = crossProject(JSPlatform, JVMPlatform)
   .crossType(CrossType.Pure)
   .in(file("lambda-api-gateway-proxy-http4s"))

lambda-natchez/src/main/scala/feral/lambda/natchez/HasKernel.scala

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2021 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package feral.lambda.natchez
+
+import feral.lambda.events.ApiGatewayProxyEventV2
+import natchez.Kernel
+
+trait HasKernel[Event] {
+  def extract(event: Event): Kernel
+}
+
+object HasKernel extends HasKernelLowPriority {
+  @inline def apply[E](implicit hk: HasKernel[E]): hk.type = hk
+
+  implicit val apiGateProxyEventV2Kernel: HasKernel[ApiGatewayProxyEventV2] =
+    e => Kernel(e.headers)
+}
+
+private[natchez] sealed class HasKernelLowPriority {
+  implicit def emptyKernel[E]: HasKernel[E] = _ => Kernel(Map.empty)
+}

lambda-natchez/src/main/scala/feral/lambda/natchez/LiftTrace.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2021 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package feral.lambda.natchez
+
+import cats.~>
+import natchez.Span
+import natchez.Trace
+
+// https://github.com/tpolecat/natchez/pull/448
+trait LiftTrace[F[_], G[_]] {
+  def run[A](span: Span[F])(f: Trace[G] => G[A]): F[A]
+  def liftK: F ~> G
+}

lambda-natchez/src/main/scala/feral/lambda/natchez/TracedLambda.scala

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2021 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package feral.lambda.natchez
+
+import cats.effect.kernel.MonadCancelThrow
+import feral.lambda.Lambda
+import natchez.EntryPoint
+import natchez.Trace
+
+object TracedLambda {
+  def apply[F[_]: MonadCancelThrow, G[_], Event: HasKernel, Result](entryPoint: EntryPoint[F])(
+      lambda: Trace[G] => Lambda[G, Event, Result])(
+      implicit lift: LiftTrace[F, G]): Lambda[F, Event, Result] = { (event, context) =>
+    val kernel = HasKernel[Event].extract(event)
+    entryPoint.continueOrElseRoot(context.functionName, kernel).use { span =>
+      lift.run(span)(lambda(_)(event, context.mapK(lift.liftK)))
+    }
+  }
+}

lambda/shared/src/main/scala/feral/lambda/Context.scala

@@ -16,6 +16,8 @@
 
 package feral.lambda
 
+import cats.~>
+
 import scala.concurrent.duration.FiniteDuration
 
 final case class Context[F[_]](
@@ -29,7 +31,10 @@ final case class Context[F[_]](
     identity: Option[CognitoIdentity],
     clientContext: Option[ClientContext],
     remainingTime: F[FiniteDuration]
-)
+) {
+  def mapK[G[_]](f: F ~> G): Context[G] =
+    copy(remainingTime = f(remainingTime))
+}
 
 object Context extends ContextCompanionPlatform