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HDFS-14861. Reset LowRedundancyBlocks Iterator periodically. Contributed by Stephen O'Donnell. 

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
This commit is contained in:
Stephen O'Donnell 2020-02-25 13:27:53 -08:00 committed by Wei-Chiu Chuang
parent 8dc079455e
commit 900430b990
5 changed files with 105 additions and 3 deletions
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4
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
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@ -244,6 +244,10 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
public static final String DFS_NAMENODE_REDUNDANCY_INTERVAL_SECONDS_KEY =
HdfsClientConfigKeys.DeprecatedKeys.DFS_NAMENODE_REDUNDANCY_INTERVAL_SECONDS_KEY;
public static final int DFS_NAMENODE_REDUNDANCY_INTERVAL_SECONDS_DEFAULT = 3;
public static final String DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS =
"dfs.namenode.redundancy.queue.restart.iterations";
public static final int
DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS_DEFAULT = 2400;
public static final String DFS_NAMENODE_REPLICATION_MIN_KEY =
HdfsClientConfigKeys.DeprecatedKeys.DFS_NAMENODE_REPLICATION_MIN_KEY;
public static final int DFS_NAMENODE_REPLICATION_MIN_DEFAULT = 1;

35
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
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@ -300,6 +300,16 @@ public class BlockManager implements BlockStatsMXBean {
*/
private final long redundancyRecheckIntervalMs;
/**
* Tracks how many calls have been made to chooseLowReduncancyBlocks since
* the queue position was last reset to the queue head. If CallsSinceReset
* crosses the threshold the next call will reset the iterators. A threshold
* of zero means the queue position will only be reset once the next of the
* queue has been reached.
*/
private int replQueueResetToHeadThreshold;
private int replQueueCallsSinceReset = 0;
/** How often to check and the limit for the storageinfo efficiency. */
private final long storageInfoDefragmentInterval;
private final long storageInfoDefragmentTimeout;
@ -572,6 +582,18 @@ public class BlockManager implements BlockStatsMXBean {
}
this.minReplicationToBeInMaintenance = (short)minMaintenanceR;
replQueueResetToHeadThreshold = conf.getInt(
DFSConfigKeys.DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS,
DFSConfigKeys.DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS_DEFAULT);
if (replQueueResetToHeadThreshold < 0) {
LOG.warn("{} is set to {} and it must be >= 0. Resetting to default {}",
DFSConfigKeys.DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS,
replQueueResetToHeadThreshold, DFSConfigKeys.
DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS_DEFAULT);
replQueueResetToHeadThreshold = DFSConfigKeys.
DFS_NAMENODE_REDUNDANCY_QUEUE_RESTART_ITERATIONS_DEFAULT;
}
long heartbeatIntervalSecs = conf.getTimeDuration(
DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY,
DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_DEFAULT, TimeUnit.SECONDS);
@ -1912,9 +1934,18 @@ public class BlockManager implements BlockStatsMXBean {
List<List<BlockInfo>> blocksToReconstruct = null;
namesystem.writeLock();
try {
// Choose the blocks to be reconstructed
boolean reset = false;
if (replQueueResetToHeadThreshold > 0) {
if (replQueueCallsSinceReset >= replQueueResetToHeadThreshold) {
reset = true;
replQueueCallsSinceReset = 0;
} else {
replQueueCallsSinceReset++;
}
}
// Choose the blocks to be reconstructed
blocksToReconstruct = neededReconstruction
.chooseLowRedundancyBlocks(blocksToProcess);
.chooseLowRedundancyBlocks(blocksToProcess, reset);
} finally {
namesystem.writeUnlock();
}

24
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/LowRedundancyBlocks.java
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@ -488,6 +488,28 @@ class LowRedundancyBlocks implements Iterable<BlockInfo> {
*/
synchronized List<List<BlockInfo>> chooseLowRedundancyBlocks(
int blocksToProcess) {
return chooseLowRedundancyBlocks(blocksToProcess, false);
}
/**
* Get a list of block lists without sufficient redundancy. The index of
* block lists represents its replication priority. Iterates each block list
* in priority order beginning with the highest priority list. Iterators use
* a bookmark to resume where the previous iteration stopped. Returns when
* the block count is met or iteration reaches the end of the lowest priority
* list, in which case bookmarks for each block list are reset to the heads
* of their respective lists.
*
* @param blocksToProcess - number of blocks to fetch from low redundancy
* blocks.
* @param resetIterators - After gathering the list of blocks reset the
* position of all queue iterators to the head of the queue so
* subsequent calls will begin at the head of the queue
* @return Return a list of block lists to be replicated. The block list
* index represents its redundancy priority.
*/
synchronized List<List<BlockInfo>> chooseLowRedundancyBlocks(
int blocksToProcess, boolean resetIterators) {
final List<List<BlockInfo>> blocksToReconstruct = new ArrayList<>(LEVEL);
int count = 0;
@ -509,7 +531,7 @@ class LowRedundancyBlocks implements Iterable<BlockInfo> {
}
}
if (priority == LEVEL) {
if (priority == LEVEL || resetIterators) {
// Reset all bookmarks because there were no recently added blocks.
for (LightWeightLinkedSet<BlockInfo> q : priorityQueues) {
q.resetBookmark();

18
hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
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@ -1136,6 +1136,24 @@
</description>
</property>
<property>
<name>dfs.namenode.redundancy.queue.restart.iterations</name>
<value>2400</value>
<description>When picking blocks from the low redundancy queues, reset the
bookmarked iterator after the set number of iterations to ensure any blocks
which were not processed on the first pass are retried before the iterators
would naturally reach their end point. This ensures blocks are retried
more frequently when there are many pending blocks or blocks are
continuously added to the queues preventing the iterator reaching its
natural endpoint.
The default setting of 2400 combined with the default of
dfs.namenode.redundancy.interval.seconds means the iterators will be reset
approximately every 2 hours.
Setting this parameter to zero disables the feature and the iterators will
be reset only when the end of all queues has been reached.
</description>
</property>
<property>
<name>dfs.namenode.accesstime.precision</name>
<value>3600000</value>

27
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestLowRedundancyBlockQueues.java
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@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs.server.blockmanagement;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.apache.hadoop.hdfs.StripedFileTestUtil;
import org.apache.hadoop.hdfs.protocol.Block;
@ -92,6 +93,32 @@ public class TestLowRedundancyBlockQueues {
queues.getHighestPriorityECBlockCount());
}
@Test
public void testQueuePositionCanBeReset() throws Throwable {
LowRedundancyBlocks queues = new LowRedundancyBlocks();
for (int i=0; i< 4; i++) {
BlockInfo block = genBlockInfo(i);
queues.add(block, 2, 0, 0, 3);
}
List<List<BlockInfo>> blocks;
// Get one block from the queue - should be block ID 0 returned
blocks = queues.chooseLowRedundancyBlocks(1, false);
assertEquals(1, blocks.get(2).size());
assertEquals(0, blocks.get(2).get(0).getBlockId());
// Get the next blocks - should be ID 1
blocks = queues.chooseLowRedundancyBlocks(1, false);
assertEquals(1, blocks.get(2).get(0).getBlockId());
// Get the next block, but also reset this time - should be ID 2 returned
blocks = queues.chooseLowRedundancyBlocks(1, true);
assertEquals(2, blocks.get(2).get(0).getBlockId());
// Get one more block and due to resetting the queue it will be block id 0
blocks = queues.chooseLowRedundancyBlocks(1, false);
assertEquals(0, blocks.get(2).get(0).getBlockId());
}
/**
* Test that adding blocks with different replication counts puts them
* into different queues.