create new DifferentialSource utility

1 files changed, 24 insertions, 0 deletions

diff --git a/kamon-core/src/main/scala/kamon/util/DifferentialSource.scala b/kamon-core/src/main/scala/kamon/util/DifferentialSource.scala
new file mode 100644
index 00000000..f2c621b0
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/util/DifferentialSource.scala
@@ -0,0 +1,24 @@
+package kamon.util
+
+/**
+  * Keeps track of the values produced by the source and produce the difference between the last two observed values
+  * when calling get. This class assumes the source increases monotonically and any produced value that violates this
+  * assumption will be dropped.
+  *
+  */
+class DifferentialSource(source: () => Long) {
+  private var previousValue = source()
+
+  def get(): Long = synchronized {
+    val currentValue = source()
+    val diff = currentValue - previousValue
+    previousValue = currentValue
+
+    if(diff < 0) 0 else diff
+  }
+}
+
+object DifferentialSource {
+  def apply(source: () => Long): DifferentialSource =
+    new DifferentialSource(source)
+}