Kenneh Yang created HDFS-14171:
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Summary: Performance improvement in Tailing EditLog
Key: HDFS-14171
URL: https://issues.apache.org/jira/browse/HDFS-14171
Project: Hadoop HDFS
Issue Type: Improvement
Components: namenode
Affects Versions: 3.0.0-alpha1, 2.9.0
Reporter: Kenneh Yang
stack:
{code:java}
Thread 456 (Edit log tailer):
State: RUNNABLE
Blocked count: 1139
Waited count: 12
Stack:
org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager.getNumLiveDataNodes(DatanodeManager.java:1259)
org.apache.hadoop.hdfs.server.blockmanagement.BlockManagerSafeMode.areThresholdsMet(BlockManagerSafeMode.java:570)
org.apache.hadoop.hdfs.server.blockmanagement.BlockManagerSafeMode.checkSafeMode(BlockManagerSafeMode.java:213)
org.apache.hadoop.hdfs.server.blockmanagement.BlockManagerSafeMode.adjustBlockTotals(BlockManagerSafeMode.java:265)
org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.completeBlock(BlockManager.java:1087)
org.apache.hadoop.hdfs.server.blockmanagement.BlockManager.forceCompleteBlock(BlockManager.java:1118)
org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.updateBlocks(FSEditLogLoader.java:1126)
org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.applyEditLogOp(FSEditLogLoader.java:468)
org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadEditRecords(FSEditLogLoader.java:258)
org.apache.hadoop.hdfs.server.namenode.FSEditLogLoader.loadFSEdits(FSEditLogLoader.java:161)
org.apache.hadoop.hdfs.server.namenode.FSImage.loadEdits(FSImage.java:892)
org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.doTailEdits(EditLogTailer.java:321)
org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.doWork(EditLogTailer.java:460)
org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.access$400(EditLogTailer.java:410)
org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread$1.run(EditLogTailer.java:427)
org.apache.hadoop.security.SecurityUtil.doAsLoginUserOrFatal(SecurityUtil.java:414)
org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.run(EditLogTailer.java:423)
Thread 455 (pool-16-thread-1):
{code}
code:
{code:java}
private boolean areThresholdsMet() {
assert namesystem.hasWriteLock();
int datanodeNum = blockManager.getDatanodeManager().getNumLiveDataNodes();
synchronized (this) {
return blockSafe >= blockThreshold && datanodeNum >= datanodeThreshold;
}
}
{code}
According to the code, each time the method areThresholdsMet() is called, the
value of {color:#FF0000}dataNodeNum{color} is need to be calculated. However,
in the scenario of {color:#FF0000}datanodeThreshold{color} is equal to 0（0 is
the default value of the configuration）, This expression datanodeNum >=
datanodeThreshold always returns true. Calling the method
{color:#FF0000}getNumLiveDataNodes(){color} is time consuming at a scale of
10,000 datanode clusters. Therefore, we add the judgment condition, and only
when the datanodeThreshold is greater than 0, the datanodeNum is calculated,
which improves the perfomance greatly.
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