Add LogWithMarker to Akka Stream #28450

akka-stream/src/main/scala/akka/stream/javadsl/SubSource.scala

@@ -5,7 +5,7 @@
 package akka.stream.javadsl
 
 import akka.NotUsed
-import akka.event.LoggingAdapter
+import akka.event.{ LogMarker, LoggingAdapter, MarkerLoggingAdapter }
 import akka.japi.{ function, Pair, Util }
 import akka.stream._
 import akka.util.ConstantFun
@@ -2395,4 +2395,98 @@ class SubSource[Out, Mat](
   def log(name: String): SubSource[Out, Mat] =
     this.log(name, ConstantFun.javaIdentityFunction[Out], null)
 
+  /**
+   * Logs elements flowing through the stream as well as completion and erroring.
+   *
+   * By default element and completion signals are logged on debug level, and errors are logged on Error level.
+   * This can be adjusted according to your needs by providing a custom [[Attributes.LogLevels]] attribute on the given Flow:
+   *
+   * The `extract` function will be applied to each element before logging, so it is possible to log only those fields
+   * of a complex object flowing through this element.
+   *
+   * Uses the given [[MarkerLoggingAdapter]] for logging.
+   *
+   * Adheres to the [[ActorAttributes.SupervisionStrategy]] attribute.
+   *
+   * '''Emits when''' the mapping function returns an element
+   *
+   * '''Backpressures when''' downstream backpressures
+   *
+   * '''Completes when''' upstream completes
+   *
+   * '''Cancels when''' downstream cancels
+   */
+  def logWithMarker(
+      name: String,
+      marker: function.Function[Out, LogMarker],
+      extract: function.Function[Out, Any],
+      log: MarkerLoggingAdapter): SubSource[Out, Mat] =
+    new SubSource(delegate.logWithMarker(name, e => marker.apply(e), e => extract.apply(e))(log))
+
+  /**
+   * Logs elements flowing through the stream as well as completion and erroring.
+   *
+   * By default element and completion signals are logged on debug level, and errors are logged on Error level.
+   * This can be adjusted according to your needs by providing a custom [[Attributes.LogLevels]] attribute on the given Flow:
+   *
+   * The `extract` function will be applied to each element before logging, so it is possible to log only those fields
+   * of a complex object flowing through this element.
+   *
+   * Uses an internally created [[MarkerLoggingAdapter]] which uses `akka.stream.Log` as it's source (use this class to configure slf4j loggers).
+   *
+   * '''Emits when''' the mapping function returns an element
+   *
+   * '''Backpressures when''' downstream backpressures
+   *
+   * '''Completes when''' upstream completes
+   *
+   * '''Cancels when''' downstream cancels
+   */
+  def logWithMarker(
+      name: String,
+      marker: function.Function[Out, LogMarker],
+      extract: function.Function[Out, Any]): SubSource[Out, Mat] =
+    this.logWithMarker(name, marker, extract, null)
+
+  /**
+   * Logs elements flowing through the stream as well as completion and erroring.
+   *
+   * By default element and completion signals are logged on debug level, and errors are logged on Error level.
+   * This can be adjusted according to your needs by providing a custom [[Attributes.LogLevels]] attribute on the given Flow:
+   *
+   * Uses the given [[MarkerLoggingAdapter]] for logging.
+   *
+   * '''Emits when''' the mapping function returns an element
+   *
+   * '''Backpressures when''' downstream backpressures
+   *
+   * '''Completes when''' upstream completes
+   *
+   * '''Cancels when''' downstream cancels
+   */
+  def logWithMarker(
+      name: String,
+      marker: function.Function[Out, LogMarker],
+      log: MarkerLoggingAdapter): SubSource[Out, Mat] =
+    this.logWithMarker(name, marker, ConstantFun.javaIdentityFunction[Out], log)
+
+  /**
+   * Logs elements flowing through the stream as well as completion and erroring.
+   *
+   * By default element and completion signals are logged on debug level, and errors are logged on Error level.
+   * This can be adjusted according to your needs by providing a custom [[Attributes.LogLevels]] attribute on the given Flow.
+   *
+   * Uses an internally created [[MarkerLoggingAdapter]] which uses `akka.stream.Log` as it's source (use this class to configure slf4j loggers).
+   *
+   * '''Emits when''' the mapping function returns an element
+   *
+   * '''Backpressures when''' downstream backpressures
+   *
+   * '''Completes when''' upstream completes
+   *
+   * '''Cancels when''' downstream cancels
+   */
+  def logWithMarker(name: String, marker: function.Function[Out, LogMarker]): SubSource[Out, Mat] =
+    this.logWithMarker(name, marker, ConstantFun.javaIdentityFunction[Out], null)
+
 }