Add middlewares to add log annotations

zio-http/src/main/scala/zio/http/Middleware.scala

@@ -170,6 +170,68 @@ object Middleware extends HandlerAspects {
     }
   }
 
+  def logAnnotate(key: => String, value: => String)(implicit trace: Trace): Middleware[Any] =
+    logAnnotate(LogAnnotation(key, value))
+
+  def logAnnotate(logAnnotation: => LogAnnotation, logAnnotations: LogAnnotation*)(implicit
+    trace: Trace,
+  ): Middleware[Any] =
+    logAnnotate((logAnnotation +: logAnnotations).toSet)
+
+  def logAnnotate(logAnnotations: => Set[LogAnnotation])(implicit trace: Trace): Middleware[Any] =
+    new Middleware[Any] {
+      def apply[Env1 <: Any, Err](routes: Routes[Env1, Err]): Routes[Env1, Err] =
+        routes.transform[Env1] { h =>
+          handler((req: Request) => ZIO.logAnnotate(logAnnotations)(h(req)))
+        }
+    }
+
+  /**
+   * Creates a middleware that will annotate log messages that are logged while
+   * a request is handled with log annotations derived from the request.
+   */
+  def logAnnotate(fromRequest: Request => Set[LogAnnotation])(implicit trace: Trace): Middleware[Any] =
+    new Middleware[Any] {
+      def apply[Env1 <: Any, Err](routes: Routes[Env1, Err]): Routes[Env1, Err] =
+        routes.transform[Env1] { h =>
+          handler((req: Request) => ZIO.logAnnotate(fromRequest(req))(h(req)))
+        }
+    }
+
+  /**
+   * Creates a middleware that will annotate log messages that are logged while
+   * a request is handled with the names and the values of the specified
+   * headers.
+   */
+  def logAnnotateHeaders(headerName: String, headerNames: String*)(implicit trace: Trace): Middleware[Any] =
+    new Middleware[Any] {
+      def apply[Env1 <: Any, Err](routes: Routes[Env1, Err]): Routes[Env1, Err] = {
+        val headers = headerName +: headerNames
+        routes.transform[Env1] { h =>
+          handler((req: Request) => {
+            val annotations = Set.newBuilder[LogAnnotation]
+            annotations.sizeHint(headers.length)
+            var i           = 0
+            while (i < headers.length) {
+              val name = headers(i)
+              annotations += LogAnnotation(name, req.headers.get(name).mkString)
+              i += 1
+            }
+            ZIO.logAnnotate(annotations.result())(h(req))
+          })
+        }
+      }
+    }
+
+  /**
+   * Creates middleware that will annotate log messages that are logged while a
+   * request is handled with the names and the values of the specified headers.
+   */
+  def logAnnotateHeaders(header: Header.HeaderType, headers: Header.HeaderType*)(implicit
+    trace: Trace,
+  ): Middleware[Any] =
+    logAnnotateHeaders(header.name, headers.map(_.name): _*)
+
   def timeout(duration: Duration)(implicit trace: Trace): Middleware[Any] =
     new Middleware[Any] {
       def apply[Env1 <: Any, Err](routes: Routes[Env1, Err]): Routes[Env1, Err] =

zio-http/src/test/scala/zio/http/LogAnnotationMiddlewareSpec.scala

@@ -0,0 +1,72 @@
+package zio.http
+
+import zio._
+import zio.test._
+
+object LogAnnotationMiddlewareSpec extends ZIOSpecDefault {
+  override def spec: Spec[TestEnvironment with Scope, Any] =
+    suite("LogAnnotationMiddlewareSpec")(
+      test("add static log annotation") {
+        val response = Routes
+          .singleton(
+            handler(ZIO.logWarning("Oh!") *> ZIO.succeed(Response.text("Hey logging!"))),
+          )
+          .@@(Middleware.logAnnotate("label", "value"))
+          .toHttpApp
+          .runZIO(Request.get("/"))
+
+        for {
+          _    <- response
+          logs <- ZTestLogger.logOutput
+          log = logs.filter(_.message() == "Oh!").head
+        } yield assertTrue(log.annotations.get("label").contains("value"))
+
+      },
+      test("add request method and path as annotation") {
+        val response = Routes
+          .singleton(
+            handler(ZIO.logWarning("Oh!") *> ZIO.succeed(Response.text("Hey logging!"))),
+          )
+          .@@(
+            Middleware.logAnnotate(req =>
+              Set(LogAnnotation("method", req.method.name), LogAnnotation("path", req.path.encode)),
+            ),
+          )
+          .toHttpApp
+          .runZIO(Request.get("/"))
+
+        for {
+          _    <- response
+          logs <- ZTestLogger.logOutput
+          log = logs.filter(_.message() == "Oh!").head
+        } yield assertTrue(
+          log.annotations.get("method").contains("GET"),
+          log.annotations.get("path").contains("/"),
+        )
+      },
+      test("add headers as annotation") {
+        val response = Routes
+          .singleton(
+            handler(ZIO.logWarning("Oh!") *> ZIO.succeed(Response.text("Hey logging!"))),
+          )
+          .@@(Middleware.logAnnotateHeaders("header"))
+          .@@(Middleware.logAnnotateHeaders(Header.UserAgent.name))
+          .toHttpApp
+          .runZIO {
+            Request
+              .get("/")
+              .addHeader("header", "value")
+              .addHeader(Header.UserAgent.Product("zio-http", Some("3.0.0")))
+          }
+
+        for {
+          _    <- response
+          logs <- ZTestLogger.logOutput
+          log = logs.filter(_.message() == "Oh!").head
+        } yield assertTrue(
+          log.annotations.get("header").contains("value"),
+          log.annotations.get(Header.UserAgent.name).contains("zio-http/3.0.0"),
+        )
+      },
+    )
+}