From f5a5e3245a8cd384d0f6f7e0f25aab3b7b380957 Mon Sep 17 00:00:00 2001
From: Ben Manes <ben.manes@gmail.com>
Date: Mon, 22 Feb 2021 17:14:41 -0800
Subject: [PATCH] Add putIfAbsent optimistic fastpath (#506)

---
 build.gradle                                  |  2 +-
 .../caffeine/cache/BoundedLocalCache.java     | 22 +++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/build.gradle b/build.gradle
index ad3d08bfb6..26107bf36c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -42,7 +42,7 @@ allprojects {
   version.with {
     major = 2 // incompatible API changes
     minor = 9 // backwards-compatible additions
-    patch = 0 // backwards-compatible bug fixes
+    patch = 1 // backwards-compatible bug fixes
     releaseBuild = rootProject.hasProperty('release')
   }
 }
diff --git a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java
index 9f4826bb1c..38595edf6c 100644
--- a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java
+++ b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/BoundedLocalCache.java
@@ -2029,12 +2029,34 @@ public Map<K, V> getAllPresent(Iterable<?> keys) {
           if (prior == node) {
             afterWrite(new AddTask(node, newWeight));
             return null;
+          } else if (onlyIfAbsent) {
+            // An optimistic fast path to avoid unnecessary locking
+            V currentValue = prior.getValue();
+            if ((currentValue != null) && !hasExpired(prior, now)) {
+              if (!isComputingAsync(prior)) {
+                tryExpireAfterRead(prior, key, currentValue, expiry(), now);
+                setAccessTime(prior, now);
+              }
+              afterRead(prior, now, /* recordHit */ false);
+              return currentValue;
+            }
           }
         } else {
           prior = data.putIfAbsent(node.getKeyReference(), node);
           if (prior == null) {
             afterWrite(new AddTask(node, newWeight));
             return null;
+          } else if (onlyIfAbsent) {
+            // An optimistic fast path to avoid unnecessary locking
+            V currentValue = prior.getValue();
+            if ((currentValue != null) && !hasExpired(prior, now)) {
+              if (!isComputingAsync(prior)) {
+                tryExpireAfterRead(prior, key, currentValue, expiry(), now);
+                setAccessTime(prior, now);
+              }
+              afterRead(prior, now, /* recordHit */ false);
+              return currentValue;
+            }
           }
         }
       } else if (onlyIfAbsent) {