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HADOOP-6133. Add a caching layer to Configuration::getClassByName to

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alleviate a performance regression introduced in a compatibility layer.
Contributed by Todd Lipcon


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@812285 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Christopher Douglas 2009-09-07 21:54:45 +00:00
parent 9b0b37e410
commit f95ec3f5bf
2 changed files with 30 additions and 2 deletions
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7
CHANGES.txt
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@ -512,7 +512,8 @@ Trunk (unreleased changes)
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 @@ Trunk (unreleased changes)
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

25
src/java/org/apache/hadoop/conf/Configuration.java
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@ -170,6 +170,9 @@ public class Configuration implements Iterable<Map.Entry<String,String>>,
*/
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 @@ public void setStrings(String name, String... values) {
* @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;
}
/**