From 82e0bdbad58db8180e344b7f2ee5c96b626509b7 Mon Sep 17 00:00:00 2001
From: Mikhail Bezoyan <mbezoyan@twitter.com>
Date: Thu, 25 Jan 2024 17:08:32 +0000
Subject: [PATCH] [finagle-stats] Do not allocate a new IndexedSeq on every
 metric lookup

Differential Revision: https://phabricator.twitter.biz/D1121923
---
 .../main/scala/com/twitter/finagle/stats/MetricBuilder.scala | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/util-stats/src/main/scala/com/twitter/finagle/stats/MetricBuilder.scala b/util-stats/src/main/scala/com/twitter/finagle/stats/MetricBuilder.scala
index 12ba7bb94e..de95e7b5d1 100644
--- a/util-stats/src/main/scala/com/twitter/finagle/stats/MetricBuilder.scala
+++ b/util-stats/src/main/scala/com/twitter/finagle/stats/MetricBuilder.scala
@@ -78,6 +78,8 @@ object MetricBuilder {
 
   val NoDescription: String = "No description provided"
 
+  private[this] val EmptyPercentiles = IndexedSeq.empty
+
   /**
    * Construct a MethodBuilder.
    *
@@ -105,7 +107,8 @@ object MetricBuilder {
     relativeName: Seq[String] = Seq.empty,
     processPath: Option[String] = None,
     histogramFormat: HistogramFormat = HistogramFormat.Default,
-    percentiles: IndexedSeq[Double] = IndexedSeq.empty,
+    percentiles: IndexedSeq[Double] =
+      EmptyPercentiles, // IndexedSeq.empty creates a new collection on every call
     isStandard: Boolean = false,
     metricType: MetricType,
   ): MetricBuilder = {