From 9fa6264a1e0427c276af7819c84bbd547fa35b32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sa=C5=A1a=20=C5=BDivkov?= <sasa.zivkov@sap.com>
Date: Fri, 2 Mar 2018 11:29:16 +0100
Subject: [PATCH] Project name locks: use Striped locks instead of Cache of
 locks

Based on the review comments from Ben Manes in [1], using Cache of locks
is prone to races. Using Striped locks technique is a better technique
for this use case.

[1] https://gerrit-review.googlesource.com/145750

Bug: Issue 7903
Change-Id: I94868904befc0f0454ae518f79888a8473ad97c2
---
 .../DefaultProjectNameLockManager.java        | 25 +++----------------
 1 file changed, 3 insertions(+), 22 deletions(-)

diff --git a/java/com/google/gerrit/server/project/DefaultProjectNameLockManager.java b/java/com/google/gerrit/server/project/DefaultProjectNameLockManager.java
index 8c9bec73ca..3fb5d2af7c 100644
--- a/java/com/google/gerrit/server/project/DefaultProjectNameLockManager.java
+++ b/java/com/google/gerrit/server/project/DefaultProjectNameLockManager.java
@@ -14,17 +14,12 @@
 
 package com.google.gerrit.server.project;
 
-import com.google.common.cache.CacheBuilder;
-import com.google.common.cache.CacheLoader;
-import com.google.common.cache.LoadingCache;
+import com.google.common.util.concurrent.Striped;
 import com.google.gerrit.extensions.registration.DynamicItem;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.inject.AbstractModule;
 import com.google.inject.Singleton;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
 
 @Singleton
 public class DefaultProjectNameLockManager implements ProjectNameLockManager {
@@ -37,24 +32,10 @@ public class DefaultProjectNameLockManager implements ProjectNameLockManager {
     }
   }
 
-  LoadingCache<Project.NameKey, Lock> lockCache =
-      CacheBuilder.newBuilder()
-          .maximumSize(1024)
-          .expireAfterAccess(5, TimeUnit.MINUTES)
-          .build(
-              new CacheLoader<Project.NameKey, Lock>() {
-                @Override
-                public Lock load(Project.NameKey key) throws Exception {
-                  return new ReentrantLock();
-                }
-              });
+  Striped<Lock> locks = Striped.lock(10);
 
   @Override
   public Lock getLock(Project.NameKey name) {
-    try {
-      return lockCache.get(name);
-    } catch (ExecutionException e) {
-      throw new RuntimeException(e);
-    }
+    return locks.get(name);
   }
 }