Template Script
#!/bin/bash

set -x

# This script should be set up as a cron job on Unravel edge node to run every 24 hours once. Ondemand Fsimage is triggered
# every day at 00:00 UTC hours. This script should be set up in such a way that the Parsed Fsimage is available some time
# before 00:00 UTC on Unravel core node. For achieving that, the following times must be considered
# 1. Time to fetch Fsimage from Namenode using hdfs dfsadmin -fetchImage command
# 2. Time to parse Fsimage into TAB separated text file using hdfs oiv command
# 3. Time to copy parsed Fsimage to Unravel core node (using rsync)
# The above three times should be found out manually and cron job should run at such a time that parsed Fsimage is
# available a little before 00:00 UTC so that Ondedmand Fsimage deals with relatively fresh Fsimage data. Please note
# this is not a must for Ondemand Fsimage functionality, but just for seeing as fresh data as possible

# Fetching Fsimage requires dfsadmin privilege for the user running the command.
# 1. In non Kerberised cluster, we must run this script as that user (or any other mechanism like logging into that user
# without prompt just for running the dfsadmin command or setting setuid bit on this script so that it runs as that user
# always etc.)
# 2. In Kerberised cluster, we must do kinit for the user/service having dfsadmin privilege (typically hdfs has that
# permission.

# As described above, hdfs dfsadmin -fetchImage command requires that the user running the command must have dfsadmin privilege.
# Thus this cron job
# 1. Must run as that user in non Kerberized environment
# 2. Have kinit done as the dfsadmin user
# If a kinit needs to be done, please add it below


# Configure Unravel Edge node specific variables here. In order for rsync to work without a password prompt, the
# public SSH key of the user must be added to UNRAVEL_CORE_NODE_USER's $HOME/.ssh/authorized_keys file. In
# addition, the Unravel edge node hostname must be added as a known_host to Unravel core node for this. This user can
# be different that the dfsadmin user earlier.
CLUSTER_UID=default
UNRAVEL_CORE_NODE_HOSTNAME=xyz.unraveldata.com
UNRAVEL_CORE_NODE_USER=unravel
FSIMAGE_DESTINATION_BASEDIR=<Unravel_installation_dir>/unravel/data/tmp/reports/fsimage

mkdir /tmp/$$
if [ $? -ne 0 ]
then
 echo "Failed to mkdir /tmp/$$"
 exit 1
fi

hdfs dfsadmin -fetchImage /tmp/$$
if [ $? -ne 0 ]
then
 echo "Failed to fetch Fsimage"
 exit 1
fi

hdfs oiv -i /tmp/$$/fs* -o /tmp/$$/fsimage.txt -p Delimited -t /tmp/$$/fsimage.tmp
if [ $? -ne 0 ]
then
 echo "Failed to parse Fsimage"
 exit 1
fi

rsync /tmp/$$/fsimage.txt ${UNRAVEL_CORE_NODE_USER}@${UNRAVEL_CORE_NODE_HOSTNAME}:${FSIMAGE_DESTINATION_BASEDIR}/${CLUSTER_UID}
if [ $? -ne 0 ]
then
 echo "Failed to upload Fsimage /tmp/$$/fsimage.txt to @${UNRAVEL_CORE_NODE_HOSTNAME} at ${FSIMAGE_DESTINATION_BASEDIR}/${CLUSTER_UID}"
 exit 1
fi

rm -rf /tmp/$$