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From Stuart Smith <stu24m...@yahoo.com>
Subject hadoop log timestamps & file timestamps not same as system time
Date Wed, 21 Apr 2010 22:46:30 GMT
Hello,
  I've noticed an odd situation:

The timestamps in my hadoop namenode log (and filesystem) appear to be an hour behind the
actual time on the system (as supplied by `date`). 

I checked that this wasn't user error by stopping and starting hadoop, and checking the most
recent messages (as well as the last time the file was modified).

For example, you can see the last modified time, and the timestamp on the shutdown log message
different significantly:

stu@ubuntu-namenode:~/hadoop/logs$ ls -l hadoop-stu-namenode-ubuntu-namenode.log
-rw-r--r-- 1 stu stu 22148124 2010-04-21 15:33 hadoop-stu-namenode-ubuntu-namenode.log
stu@ubuntu-namenode:~/hadoop/logs$ tail -f hadoop-stu-namenode-ubuntu-namenode.log
....
2010-04-21 14:33:19,032 INFO org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG:

/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at ubuntu-namenode/192.168.193.87
************************************************************/

I also checked this while hadoop was running: the messages are consistently an hour behind.

More troubling, this appears affect the filesystem timestamps as well.

stu@ubuntu-namenode:~/hadoop/bin$ date
Wed Apr 21 15:53:34 PDT 2010
stu@ubuntu-namenode:~/hadoop/bin$ ./hadoop dfs -touchz /test
stu@ubuntu-namenode:~/hadoop/bin$ ./hadoop dfs -ls /
Found 2 items
drwxr-xr-x   - stu supergroup          0 2010-04-20 16:51 /home
-rw-r--r--   3 stu supergroup          0 2010-04-21 14:53 /test


Interestingly, the datanodes appear to be fine:

stu@ubuntu-hadoop-2:~/hadoop/logs$ ls -l hadoop-stu-datanode-ubuntu-hadoop-2.log
-rw-r--r-- 1 stu stu 4918505 2010-04-21 15:47 hadoop-stu-datanode-ubuntu-hadoop-2.log
stu@ubuntu-hadoop-2:~/hadoop/logs$ tail -n 1 hadoop-stu-datanode-ubuntu-hadoop-2.log
2010-04-21 15:47:21,875 INFO org.mortbay.log: jetty-6.1.14

Is there something wrong here? Am I just doing something crazy/dumb?

Note that I discovered this after getting some rather odd behavior from hbase - hbase appears
to work fine, except it's continually adding the regionservers onto the list so, in my itty-bitty
cluster of about 4 machines + 1 namenode, the master reports back ~ 1000s of regionservers
and growing.. There are indications timing issues involved in that as well, but I figure I
should get hdfs working first :)

Note that I do have NTP running to keep all these boxes in sync, but the NTP server will go
down for an hour or so intermittently (due to some network issues that don't involve the hadoop
cluster). All the system times on the machines appear to be (at least) within a few seconds
of each other. 

I'm running hadoop 0.20.2

Any thoughts? Any debugging guidance? I'm pretty stumped.

Take care,
  -stu


      

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