Han Xiao created HDFS-4130:
------------------------------
Summary: The reading for editlog at NN starting using bkjm is not
efficient
Key: HDFS-4130
URL: https://issues.apache.org/jira/browse/HDFS-4130
Project: Hadoop HDFS
Issue Type: Improvement
Components: ha, performance
Affects Versions: 2.0.2-alpha
Reporter: Han Xiao
Now, the method of BookKeeperJournalManager.selectInputStreams is written like:
while (true) {
EditLogInputStream elis;
try {
elis = getInputStream(fromTxId, inProgressOk);
} catch (IOException e) {
LOG.error(e);
return;
}
if (elis == null) {
return;
}
streams.add(elis);
if (elis.getLastTxId() == HdfsConstants.INVALID_TXID) {
return;
}
fromTxId = elis.getLastTxId() + 1;
}
EditLogInputstream is got from getInputStream(), which will read the ledgers
from zookeeper in each calling.
This will be a larger cost of times when the the number ledgers becomes large.
The reading of ledgers from zk is not necessary for every calling of
getInputStream().
The log of time wasting here is as follows:
2012-10-30 16:44:52,995 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
Caching file names occuring more than 10 times
2012-10-30 16:49:24,643 INFO
hidden.bkjournal.org.apache.bookkeeper.proto.PerChannelBookieClient:
Successfully connected to bookie: /167.52.1.121:318
The stack of the process when blocking between the two lines of log is like:
"main" prio=10 tid=0x000000004011f000 nid=0x39ba in Object.wait()
[0x00007fca020fe000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:485)
at
hidden.bkjournal.org.apache.zookeeper.ClientCnxn.submitRequest(ClientCnxn.java:1253)
- locked <0x00000006fb8495a8> (a
hidden.bkjournal.org.apache.zookeeper.ClientCnxn$Packet)
at
hidden.bkjournal.org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1129)
at
org.apache.hadoop.contrib.bkjournal.utils.RetryableZookeeper.getData(RetryableZookeeper.java:501)
at
hidden.bkjournal.org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1160)
at
org.apache.hadoop.contrib.bkjournal.EditLogLedgerMetadata.read(EditLogLedgerMetadata.java:113)
at
org.apache.hadoop.contrib.bkjournal.BookKeeperJournalManager.getLedgerList(BookKeeperJournalManager.java:725)
at
org.apache.hadoop.contrib.bkjournal.BookKeeperJournalManager.getInputStream(BookKeeperJournalManager.java:442)
at
org.apache.hadoop.contrib.bkjournal.BookKeeperJournalManager.selectInputStreams(BookKeeperJournalManager.java:480)
betweent different time, the diff of stack is:
diff stack stack2
1c1
< 2012-10-30 16:44:53
---
> 2012-10-30 16:46:17
106c106
< - locked <0x00000006fb8495a8> (a
hidden.bkjournal.org.apache.zookeeper.ClientCnxn$Packet)
---
> - locked <0x00000006fae58468> (a
> hidden.bkjournal.org.apache.zookeeper.ClientCnxn$Packet)
In our environment, the waiting time could even reach to tens of minutes.
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