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how to rotate the HDFS gc logs on data node machines


hi all

we are trying to rotate the gc logs on workers machines according to the following

we add the line

-XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2K

inside HADOOP_DATANODE_OPTS variable

in HDFS --> Advanced hadoop-env

as the following:

<br>export HADOOP_DATANODE_OPTS="-server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/$USER/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2K -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms{{dtnode_heapsize}} -Xmx{{dtnode_heapsize}},DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT ${HADOOP_DATANODE_OPTS}"

but we get on worker machine ( data node under /var/log/hadoop/hdfs ) , the follwing

-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:33
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:35
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:36
-rw-r--r--  1 hdfs hadoop   1504 Aug 26 20:37
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:38
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:40
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:41
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:43
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:44
-rw-r--r--  1 hdfs hadoop   1035 Aug 26 20:46
-rw-r--r--  1 hdfs hadoop    727 Aug 26 20:46
-rw-r--r--  1 hdfs hadoop   3905 Aug 26 20:46 gc.log-201808262031.0.current
-rw-r--r--  1 hdfs hadoop    727 Aug 26 20:46
-rw-r--r--. 1 hdfs hadoop 101346 Aug 26 21:53 SecurityAuth.audit
-rw-r--r--  1 hdfs hadoop   7488 Aug 27 06:25 gc.log-201808262046
-rw-r--r--  1 hdfs hadoop    727 Aug 27 06:28
-rw-r--r--  1 hdfs hadoop   3651 Aug 27 06:28 gc.log-201808270625.0.current
-rw-r--r--  1 hdfs hadoop    727 Aug 27 06:29
-rw-r--r--  1 hdfs hadoop    727 Aug 27 06:29
-rw-r--r--  1 hdfs hadoop   2940 Aug 27 06:29 gc.log-201808270629.0.current
-rw-r--r--  1 hdfs hadoop 378069 Aug 27 06:34

why gc.log.... are not rotated and comes with "0.current"

what is wrong with my configuration?

** we also try the following but this isn't worked

In hadoop-env template wherever you find -XX:+PrintGCDetails parameter you can add -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M

For example:


HADOOP_JOBTRACKER_OPTS="-server -XX:ParallelGCThreads=8 -XX:+UseConcMarkSweepGC -XX:ErrorFile={{hdfs_log_dir_prefix}}/$USER/hs_err_pid%p.log -XX:NewSize={{jtnode_opt_newsize}} -XX:MaxNewSize={{jtnode_opt_maxnewsize}} -Xloggc:{{hdfs_log_dir_prefix}}/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xmx{{jtnode_heapsize}},DRFAS -Dmapred.audit.logger=INFO,MRAUDIT -Dhadoop.mapreduce.jobsummary.logger=INFO,JSA ${HADOOP_JOBTRACKER_OPTS}"


HADOOP_JOBTRACKER_OPTS="-server -XX:ParallelGCThreads=8 -XX:+UseConcMarkSweepGC -XX:ErrorFile={{hdfs_log_dir_prefix}}/$USER/hs_err_pid%p.log -XX:NewSize={{jtnode_opt_newsize}} -XX:MaxNewSize={{jtnode_opt_maxnewsize}} -Xloggc:{{hdfs_log_dir_prefix}}/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails <strong>-XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M </strong>-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xmx{{jtnode_heapsize}},DRFAS -Dmapred.audit.logger=INFO,MRAUDIT -Dhadoop.mapreduce.jobsummary.logger=INFO,JSA ${HADOOP_JOBTRACKER_OPTS}"

Master Mentor

@Michael Bronson

If you just want to quickly fill the GC log to see the log rotation then try this instead of using "cat" comamand to add content inside the actual current GC log file.

# su - hdfs
# /usr/jdk64/jdk1.8.0_112/bin/jcmd `cat /var/run/hadoop/hdfs/`

Use the "jcmd" utility to explicitly trigger the GC many times. So after running this command around 20-30 times you will see that the GC log of data node gets rotated and in the current GC log you will see some messages like:

2018-08-27 08:11:07 GC log file has reached the maximum size. Saved as /var/log/hadoop/hdfs/gc.log-201808270803.0


I see the log rotations works as expected as following:

-rw-r--r--. 1 hdfs hadoop     10617 Aug 27 08:12 gc.log-201808270803.1
-rw-r--r--. 1 hdfs hadoop     10615 Aug 27 08:13 gc.log-201808270803.2
-rw-r--r--. 1 hdfs hadoop     10616 Aug 27 08:13 gc.log-201808270803.3
-rw-r--r--. 1 hdfs hadoop      4001 Aug 27 08:13 gc.log-201808270803.4.current


View solution in original post


Master Mentor

@Michael Bronson

I see that you are setting the value to 2K as -XX:GCLogFileSize=2K

However as per the JVM option the minimum value for log rotation should be greater than 8KB, Can you please try with 8KB greater value.

The size of the log file at which point the log will be rotated, must be >= 8K.

Master Mentor

@Michael Bronson

Also after setting the value for this parameter to >8K please make sure that the correct value is being reflected to the JVM options when you run the "ps -ef | grep $PROCESS" command



we still get the same results ( we set 10K ) - as gc.log-201808270653.0.current , gc.log-201808270656.0.current

-rw-r--r--  1 hdfs hadoop   3859 Aug 27 06:53 gc.log-201808270629.0.current
-rw-r--r--  1 hdfs hadoop    727 Aug 27 06:53
-rw-r--r--  1 hdfs hadoop   3653 Aug 27 06:56 gc.log-201808270653.0.current
-rw-r--r--  1 hdfs hadoop    727 Aug 27 06:56
-rw-r--r--  1 hdfs hadoop 518292 Aug 27 06:56
-rw-r--r--  1 hdfs hadoop   3658 Aug 27 06:56 gc.log-201808270656.0.current


and we verify 10K it reflect from proceess

 ps -ef | grep 10K
hdfs     109919      1 18 06:56 ?        00:00:25 /usr/jdk64/jdk1.8.0_112/bin/java -Dproc_datanode -Xmx1024m -Dhdp.version= -Dhdp.version= -Dhdp.version= -Dhadoop.log.dir=/var/log/hadoop/hdfs -Dhadoop.log.file=hadoop.log -Dhadoop.home.dir=/usr/hdp/ -Dhadoop.root.logger=INFO,console -Djava.library.path=:/usr/hdp/ -Dhadoop.policy.file=hadoop-policy.xml -Dhdp.version= -Dhadoop.log.dir=/var/log/hadoop/hdfs -Dhadoop.home.dir=/usr/hdp/ -Dhadoop.root.logger=INFO,RFA -Djava.library.path=:/usr/hdp/ -Dhadoop.policy.file=hadoop-policy.xml -server -server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/hdfs/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/hdfs/gc.log-201808270656 -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=10K -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms1024m -Xmx1024m,DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT -server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/hdfs/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/hdfs/gc.log-201808270656 -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=10K -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms1024m -Xmx1024m,DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT -server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/hdfs/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/hdfs/gc.log-201808270656 -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=10K -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms1024m -Xmx1024m,DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT,RFAS org.apache.hadoop.hdfs.server.datanode.DataNode

Master Mentor

@Michael Bronson

I see that your GC log file is around "3658" (around 3K) currently so it should get rotated after 10K.


@Jay another quastion can we set the "

  1. -XX:+PrintGCTimeStamps-XX:+UseGCLogFileRotation-XX:NumberOfGCLogFiles=5-XX:GCLogFileSize=10K" , in the end of the line? instead i the middle ?


HADOOP_DATANODE_OPTS="-server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/$USER/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails  -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms{{dtnode_heapsize}} -Xmx{{dtnode_heapsize}},DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT ${HADOOP_DATANODE_OPTS} -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2K"

Master Mentor

@Michael Bronson

As per JVM specification if we have duplicate JVM flags set for a process then the parameter which is set at the end will take precedence. Hence it is always better to set our own custom values at the end of the JVM options (instead of middle), Else there are chances that our values might get overridden.

So better to set the JVM parameters after the default parameters.

as following: hadoop-env templte (inside {% else %} block because our JDK might be JDK8)

      export HADOOP_DATANODE_OPTS="-server -XX:ParallelGCThreads=4 -XX:+UseConcMarkSweepGC -XX:ErrorFile=/var/log/hadoop/$USER/hs_err_pid%p.log -XX:NewSize=200m -XX:MaxNewSize=200m -Xloggc:/var/log/hadoop/$USER/gc.log-`date +'%Y%m%d%H%M'` -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xms{{dtnode_heapsize}} -Xmx{{dtnode_heapsize}},DRFAS -Dhdfs.audit.logger=INFO,DRFAAUDIT ${HADOOP_DATANODE_OPTS} -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly -XX:+PrintGCTimeStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=10K -verbose:gc"


I will check it when it will be more then 10K



@Jay , I see that the log still 4K

 du -sh * | grep  gc.log-201808270656.0.current
4.0K gc.log-201808270656.0.current

is it possible to increase this log in order to see if it will rotate ?