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HDFS-11345. Document the configuration key for FSNamesystem lock fairness. Contributed by Erik Krogen.

This commit is contained in:
Akira Ajisaka 2017-06-20 16:35:54 +09:00
parent 15964ef147
commit 2c769167db
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4 changed files with 22 additions and 4 deletions
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4
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
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@ -423,6 +423,10 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
public static final long
DFS_NAMENODE_MAX_LOCK_HOLD_TO_RELEASE_LEASE_MS_DEFAULT = 25;
public static final String DFS_NAMENODE_FSLOCK_FAIR_KEY =
"dfs.namenode.fslock.fair";
public static final boolean DFS_NAMENODE_FSLOCK_FAIR_DEFAULT = true;
public static final String DFS_NAMENODE_LOCK_DETAILED_METRICS_KEY =
"dfs.namenode.lock.detailed-metrics.enabled";
public static final boolean DFS_NAMENODE_LOCK_DETAILED_METRICS_DEFAULT =

5
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystemLock.java
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@ -32,6 +32,8 @@ import org.apache.hadoop.util.Timer;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_LOCK_SUPPRESS_WARNING_INTERVAL_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_LOCK_SUPPRESS_WARNING_INTERVAL_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_FSLOCK_FAIR_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_FSLOCK_FAIR_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LOCK_DETAILED_METRICS_DEFAULT;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LOCK_DETAILED_METRICS_KEY;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_READ_LOCK_REPORTING_THRESHOLD_MS_DEFAULT;
@ -113,7 +115,8 @@ class FSNamesystemLock {
@VisibleForTesting
FSNamesystemLock(Configuration conf,
MutableRatesWithAggregation detailedHoldTimeMetrics, Timer timer) {
boolean fair = conf.getBoolean("dfs.namenode.fslock.fair", true);
boolean fair = conf.getBoolean(DFS_NAMENODE_FSLOCK_FAIR_KEY,
DFS_NAMENODE_FSLOCK_FAIR_DEFAULT);
FSNamesystem.LOG.info("fsLock is fair: " + fair);
this.coarseLock = new ReentrantReadWriteLock(fair);
this.timer = timer;

10
hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
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@ -2759,6 +2759,16 @@
</description>
</property>
<property>
<name>dfs.namenode.fslock.fair</name>
<value>true</value>
<description>If this is true, the FS Namesystem lock will be used in Fair mode,
which will help to prevent writer threads from being starved, but can provide
lower lock throughput. See java.util.concurrent.locks.ReentrantReadWriteLock
for more information on fair/non-fair locks.
</description>
</property>
<property>
<name>dfs.namenode.startup.delay.block.deletion.sec</name>
<value>0</value>

7
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSNamesystemLock.java
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@ -40,6 +40,7 @@ import java.util.concurrent.TimeoutException;
import java.util.regex.Pattern;
import static org.junit.Assert.*;
import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_FSLOCK_FAIR_KEY;
import static org.apache.hadoop.test.MetricsAsserts.assertCounter;
import static org.apache.hadoop.test.MetricsAsserts.assertGauge;
@ -53,11 +54,11 @@ public class TestFSNamesystemLock {
public void testFsLockFairness() throws IOException, InterruptedException{
Configuration conf = new Configuration();
conf.setBoolean("dfs.namenode.fslock.fair", true);
conf.setBoolean(DFS_NAMENODE_FSLOCK_FAIR_KEY, true);
FSNamesystemLock fsnLock = new FSNamesystemLock(conf, null);
assertTrue(fsnLock.coarseLock.isFair());
conf.setBoolean("dfs.namenode.fslock.fair", false);
conf.setBoolean(DFS_NAMENODE_FSLOCK_FAIR_KEY, false);
fsnLock = new FSNamesystemLock(conf, null);
assertFalse(fsnLock.coarseLock.isFair());
}
@ -103,7 +104,7 @@ public class TestFSNamesystemLock {
final int threadCount = 3;
final CountDownLatch latch = new CountDownLatch(threadCount);
final Configuration conf = new Configuration();
conf.setBoolean("dfs.namenode.fslock.fair", true);
conf.setBoolean(DFS_NAMENODE_FSLOCK_FAIR_KEY, true);
final FSNamesystemLock rwLock = new FSNamesystemLock(conf, null);
rwLock.writeLock();
ExecutorService helper = Executors.newFixedThreadPool(threadCount);