Avoid allocating lambda in PercentileTimer.computeIfAbsent (#1128)

PercentileTimer.computeIfAbsent would delegate to Utils.computeIfAbsent, which actually
eagerly calls get and then putIfAbsent if the timer is not in the underlying map. Just directly
do that to avoid needing to allocate a lambda in the case the timer is present. The same
change has been applied to PercentileDistributionSummary.

---------

Co-authored-by: Brian Harrington <brharrington@gmail.com>

build.gradle

@@ -113,7 +113,7 @@ subprojects {
     profilers = ['stack', 'gc']
     includeTests = false
     duplicateClassesStrategy = DuplicatesStrategy.WARN
-    includes = ['.*Caching.*']
+    includes = ['.*PercentileTimers.*']
   }
 
   checkstyle {

spectator-api/src/main/java/com/netflix/spectator/api/histogram/PercentileDistributionSummary.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 Netflix, Inc.
+ * Copyright 2014-2024 Netflix, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@
 import com.netflix.spectator.api.Measurement;
 import com.netflix.spectator.api.Registry;
 import com.netflix.spectator.api.Statistic;
-import com.netflix.spectator.api.Utils;
 import com.netflix.spectator.api.patterns.IdBuilder;
 import com.netflix.spectator.api.patterns.TagsBuilder;
 
@@ -66,8 +65,20 @@ public final class PercentileDistributionSummary implements DistributionSummary
    */
   private static PercentileDistributionSummary computeIfAbsent(
       Registry registry, Id id, long min, long max) {
-    Object summary = Utils.computeIfAbsent(
-        registry.state(), id, i -> new PercentileDistributionSummary(registry, id, min, max));
+    // Inlined:
+    // Object summary = Utils.computeIfAbsent(
+    //        registry.state(), id, i -> new PercentileDistributionSummary(registry, id, min, max));
+    //
+    // The lambda needs to capture the parameters for registry, min, and max which can lead to
+    // a high allocation rate for the lambda instance.
+    Object summary = registry.state().get(id);
+    if (summary == null) {
+      PercentileDistributionSummary newSummary = new PercentileDistributionSummary(registry, id, min, max);
+      summary = registry.state().putIfAbsent(id, newSummary);
+      if (summary == null) {
+        return newSummary;
+      }
+    }
     return (summary instanceof PercentileDistributionSummary)
         ? ((PercentileDistributionSummary) summary).withRange(min, max)
         : new PercentileDistributionSummary(registry, id, min, max);

spectator-api/src/main/java/com/netflix/spectator/api/histogram/PercentileTimer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2023 Netflix, Inc.
+ * Copyright 2014-2024 Netflix, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@
 import com.netflix.spectator.api.Registry;
 import com.netflix.spectator.api.Statistic;
 import com.netflix.spectator.api.Timer;
-import com.netflix.spectator.api.Utils;
 import com.netflix.spectator.api.patterns.IdBuilder;
 import com.netflix.spectator.api.patterns.TagsBuilder;
 
@@ -72,8 +71,20 @@ public final class PercentileTimer implements Timer {
    * site.
    */
   private static PercentileTimer computeIfAbsent(Registry registry, Id id, long min, long max) {
-    Object timer = Utils.computeIfAbsent(
-        registry.state(), id, i -> new PercentileTimer(registry, id, min, max));
+    // Inlined:
+    // Object timer = Utils.computeIfAbsent(
+    //        registry.state(), id, i -> new PercentileTimer(registry, id, min, max));
+    //
+    // The lambda needs to capture the parameters for registry, min, and max which can lead to
+    // a high allocation rate for the lambda instance.
+    Object timer = registry.state().get(id);
+    if (timer == null) {
+      PercentileTimer newTimer = new PercentileTimer(registry, id, min, max);
+      timer = registry.state().putIfAbsent(id, newTimer);
+      if (timer == null) {
+        return newTimer;
+      }
+    }
     return (timer instanceof PercentileTimer)
         ? ((PercentileTimer) timer).withRange(min, max)
         : new PercentileTimer(registry, id, min, max);