Script to check that both NameNodes are alive in HDFS HA configuration and will force failover to the preferred NameNode

hdfs-ha-namenode-failback.sh

#!/bin/bash
#
# This script will check that both NameNodes are alive in HDFS HA
# configuration and will force failover to the preferred NameNode.
#
# Author: Stas Alekseev <[email protected]>
#

ACTIVE_NAMENODE=nn1
STANDBY_NAMENODE=nn2

if [ ${USER} != "hdfs" ]; then
  echo "This script must be run as hdfs user."
  exit 1
fi

# Check that both NameNodes are alive
hdfs haadmin -checkHealth ${ACTIVE_NAMENODE} && hdfs haadmin -checkHealth ${STANDBY_NAMENODE} || {
  printf '%s\n' 'ERROR: one of the namenodes is dead'
  exit 1
}

if [ $(hdfs haadmin -getServiceState ${ACTIVE_NAMENODE}) = "standby" ]
then
  hdfs haadmin -failover ${STANDBY_NAMENODE} ${ACTIVE_NAMENODE}
fi