Author: cdouglas
Date: Mon Sep 7 21:54:45 2009
New Revision: 812285
URL: http://svn.apache.org/viewvc?rev=812285&view=rev
Log:
HADOOP-6133. Add a caching layer to Configuration::getClassByName to
alleviate a performance regression introduced in a compatibility layer.
Contributed by Todd Lipcon
Modified:
hadoop/common/trunk/CHANGES.txt
hadoop/common/trunk/src/java/org/apache/hadoop/conf/Configuration.java
Modified: hadoop/common/trunk/CHANGES.txt
URL:
http://svn.apache.org/viewvc/hadoop/common/trunk/CHANGES.txt?rev=812285&r1=812284&r2=812285&view=diff
==============================================================================
--- hadoop/common/trunk/CHANGES.txt (original)
+++ hadoop/common/trunk/CHANGES.txt Mon Sep 7 21:54:45 2009
@@ -512,7 +512,8 @@
HADOOP-6176. Add a couple package private methods to AccessTokenHandler
for testing. (Kan Zhang via szetszwo)
- HADOOP-6182. Fix ReleaseAudit warnings (Giridharan Kesavan and Lee Tucker
via gkesavan)
+ HADOOP-6182. Fix ReleaseAudit warnings (Giridharan Kesavan and Lee Tucker
+ via gkesavan)
HADOOP-6173. Change src/native/packageNativeHadoop.sh to package all
native library files. (Hong Tang via szetszwo)
@@ -526,6 +527,10 @@
HADOOP-6231. Allow caching of filesystem instances to be disabled on a
per-instance basis. (tomwhite)
+ HADOOP-6133. Add a caching layer to Configuration::getClassByName to
+ alleviate a performance regression introduced in a compatibility layer.
+ (Todd Lipcon via cdouglas)
+
OPTIMIZATIONS
HADOOP-5595. NameNode does not need to run a replicator to choose a
Modified: hadoop/common/trunk/src/java/org/apache/hadoop/conf/Configuration.java
URL:
http://svn.apache.org/viewvc/hadoop/common/trunk/src/java/org/apache/hadoop/conf/Configuration.java?rev=812285&r1=812284&r2=812285&view=diff
==============================================================================
--- hadoop/common/trunk/src/java/org/apache/hadoop/conf/Configuration.java
(original)
+++ hadoop/common/trunk/src/java/org/apache/hadoop/conf/Configuration.java Mon
Sep 7 21:54:45 2009
@@ -170,6 +170,9 @@
*/
private static final ArrayList<String> defaultResources =
new ArrayList<String>();
+
+ private static final Map<ClassLoader, Map<String, Class<?>>>
+ CACHE_CLASSES = new WeakHashMap<ClassLoader, Map<String, Class<?>>>();
/**
* Flag to indicate if the storage of resource which updates a key needs
@@ -1029,7 +1032,27 @@
* @throws ClassNotFoundException if the class is not found.
*/
public Class<?> getClassByName(String name) throws ClassNotFoundException {
- return Class.forName(name, true, classLoader);
+ Map<String, Class<?>> map;
+
+ synchronized (CACHE_CLASSES) {
+ map = CACHE_CLASSES.get(classLoader);
+ if (map == null) {
+ map = Collections.synchronizedMap(
+ new WeakHashMap<String, Class<?>>());
+ CACHE_CLASSES.put(classLoader, map);
+ }
+ }
+
+ Class clazz = map.get(name);
+ if (clazz == null) {
+ clazz = Class.forName(name, true, classLoader);
+ if (clazz != null) {
+ // two putters can race here, but they'll put the same class
+ map.put(name, clazz);
+ }
+ }
+
+ return clazz;
}
/**
