HBase Administration - HBase Essentials - page 136

• ps : This tool is used to view the occupied memory by the processes.
The following command uses the -rss lag to view sort processes in
the descending order by their resident set size as:
$ ps auxk -rss | less
• jstat : This tool is used for monitoring the Java Virtual Machine. Run the
following command to show the summary of the garbage collection statistics
of an HRegionServer process running with the 1812 process ID and take this
summary for every 1000 milliseconds:
hadoop@slave1$ jstat -gcutil 1812 1000
Apart from the preceding tools, there are many common errors that an administrator
might encounter in a production environment. A few of them are discussed as follows:
Too many open iles error: HBase runs on top of Hadoop that opens lots of iles at
the same time. Operating systems such as Linux deine the limit (the default value
is 1024) for ile descriptors that any process might open. In case the user's open ile
count exceeds the OS-deined limit, the following error is visible:
java.io.FileNotFoundException: /usr/local/hadoop/var/dfs/data/current/subdir6/
blk_-34458031297234453 (Too many open iles)
To ix this issue, increase the open ile count for the user by adding the following
property in the /etc/security/limits.conf ile:
$ vi /etc/security/limits.conf
<username> soft nofile 65535
<username> hard nofile 65535
Also, add the following line to the /etc/pam.d/login ile:
$ vi /etc/pam.d/login
session required pam_limits.so
Once done, log out and log in again as the user and restart the Hadoop and HBase
clusters. The upper limit for iles can be veriied using the following command:
$ ulimit -n
Unable to create a new native thread error: The OS deines the limits for the use to
execute the number of processes simultaneously. With a high load and lower value
for nproc , the HBase cluster might throw an OutOfMemoryError exception as:
DataStreamer Exception: java.lang.OutOfMemoryError: unable to create new
native thread