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HDFS-4029. GenerationStamp should use an AtomicLong. Contributed by Eli Collins 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1399097 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Eli Collins 2012-10-17 05:00:04 +00:00
parent c21eece8d2
commit 7b10aa9f80
2 changed files with 16 additions and 10 deletions
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2
hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -60,6 +60,8 @@ Release 2.0.3-alpha - Unreleased
HDFS-2946. HA: Put a cap on the number of completed edits files retained HDFS-2946. HA: Put a cap on the number of completed edits files retained
by the NN. (atm) by the NN. (atm)
HDFS-4029. GenerationStamp should use an AtomicLong. (eli)
OPTIMIZATIONS OPTIMIZATIONS
BUG FIXES BUG FIXES

24
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/GenerationStamp.java
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@ -17,6 +17,8 @@
*/ */
package org.apache.hadoop.hdfs.server.common; package org.apache.hadoop.hdfs.server.common;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceAudience;
/**************************************************************** /****************************************************************
@ -35,7 +37,7 @@ public class GenerationStamp implements Comparable<GenerationStamp> {
*/ */
public static final long GRANDFATHER_GENERATION_STAMP = 0; public static final long GRANDFATHER_GENERATION_STAMP = 0;
private volatile long genstamp; private AtomicLong genstamp = new AtomicLong();
/** /**
* Create a new instance, initialized to FIRST_VALID_STAMP. * Create a new instance, initialized to FIRST_VALID_STAMP.
@ -48,35 +50,36 @@ public class GenerationStamp implements Comparable<GenerationStamp> {
* Create a new instance, initialized to the specified value. * Create a new instance, initialized to the specified value.
*/ */
GenerationStamp(long stamp) { GenerationStamp(long stamp) {
this.genstamp = stamp; genstamp.set(stamp);
} }
/** /**
* Returns the current generation stamp * Returns the current generation stamp
*/ */
public long getStamp() { public long getStamp() {
return this.genstamp; return genstamp.get();
} }
/** /**
* Sets the current generation stamp * Sets the current generation stamp
*/ */
public void setStamp(long stamp) { public void setStamp(long stamp) {
this.genstamp = stamp; genstamp.set(stamp);
} }
/** /**
* First increments the counter and then returns the stamp * First increments the counter and then returns the stamp
*/ */
public synchronized long nextStamp() { public long nextStamp() {
this.genstamp++; return genstamp.incrementAndGet();
return this.genstamp;
} }
@Override // Comparable @Override // Comparable
public int compareTo(GenerationStamp that) { public int compareTo(GenerationStamp that) {
return this.genstamp < that.genstamp ? -1 : long stamp1 = this.genstamp.get();
this.genstamp > that.genstamp ? 1 : 0; long stamp2 = that.genstamp.get();
return stamp1 < stamp2 ? -1 :
stamp1 > stamp2 ? 1 : 0;
} }
@Override // Object @Override // Object
@ -89,6 +92,7 @@ public class GenerationStamp implements Comparable<GenerationStamp> {
@Override // Object @Override // Object
public int hashCode() { public int hashCode() {
return (int) (genstamp^(genstamp>>>32)); long stamp = genstamp.get();
return (int) (stamp^(stamp>>>32));
} }
} }