1.脚本编写

#!/bin/bash

NN1_HOSTNAME=""
NN2_HOSTNAME=""
NN1_SERVICEID=""
NN2_SERVICEID=""
NN1_SERVICESTATE=""
NN2_SERVICESTATE=""

EMAIL=503757851@qq.com

#CDH_BIN_HOME=/opt/cloudera/parcels/CDH/bin
CDH_BIN_HOME=/home/hadoop/app/hadoop/bin

# 读取nameservers
ha_name=$(${CDH_BIN_HOME}/hdfs getconf -confKey dfs.nameservices)
# 读取namenodeids
namenode_serviceids=$(${CDH_BIN_HOME}/hdfs getconf -confKey dfs.ha.namenodes.${ha_name})

# 按照 , 分隔遍历namenodeids 
for node in $(echo ${namenode_serviceids//,/ }); do
        state=$(${CDH_BIN_HOME}/hdfs haadmin -getServiceState $node)

        if [ "$state" == "active" ]; then
                NN1_SERVICEID="${node}"
                NN1_SERVICESTATE="${state}"
                NN1_HOSTNAME=`echo $(${CDH_BIN_HOME}/hdfs getconf -confKey dfs.namenode.rpc-address.${ha_name}.${node}) | awk -F ':' '{print $1}'`
#echo "${NN1_HOSTNAME} : ${NN1_SERVICEID} : ${NN1_SERVICESTATE}"

        elif [ "$state" == "standby" ]; then
                NN2_SERVICEID="${node}"
                NN2_SERVICESTATE="${state}"
                NN2_HOSTNAME=`echo $(${CDH_BIN_HOME}/hdfs getconf -confKey dfs.namenode.rpc-address.${ha_name}.${node}) | awk -F ':' '{print $1}'`
                #echo "${NN2_HOSTNAME} : ${NN2_SERVICEID} : ${NN2_SERVICESTATE}"
        else
                echo "hdfs haadmin -getServiceState $node: unkown"
        fi

done

echo "                                                                "
echo "Hostname          Namenode_Serviceid              Namenode_State"
echo "${NN1_HOSTNAME}           ${NN1_SERVICEID}                ${NN1_SERVICESTATE}"
echo "${NN2_HOSTNAME}           ${NN2_SERVICEID}                ${NN2_SERVICESTATE}"
#save current NN1/2_HOSTNAME state
echo "${NN1_HOSTNAME}           ${NN1_SERVICEID}        ${NN1_SERVICESTATE}" > HDFS_HA.log
echo "${NN2_HOSTNAME}           ${NN2_SERVICEID}        ${NN2_SERVICESTATE}" >> HDFS_HA.log

# 发送邮件
# 判断文件是否存在
if [ -f HDFS_HA_LAST.log ];then
                # 取出第一列 一个元素
                HISTORYHOSTNAME=`cat HDFS_HA_LAST.log| awk '{print $1}' | head -n 1`

                # 判断namenode是否有变化
                if [ "$HISTORYHOSTNAME" != "${NN1_HOSTNAME}"  ];then

                # 有变化 发送邮件
                echo "send a mail"
                echo -e "`date "+%Y-%m-%d %H:%M:%S"` : Please to check namenode log." | mail \
                 -r "From: alertAdmin <503757851@qq.com>" \
                -s "Warn: CDH HDFS HA Failover!." ${EMAIL}

                fi

fi

cat HDFS_HA.log > HDFS_HA_LAST.log

1.1.执行脚本

此时hdfs ha没有产生failover，所以仅仅是打印了集群hdfs ha状态

[hadoop@ruozedata001 hadoop]$ ./get_hdfs_ha_state.sh 
                                                                
Hostname        Namenode_Serviceid      Namenode_State
ruozedata002        nn2     active
ruozedata001        nn1     standby

2.模拟failover

[hadoop@ruozedata001 ~]$ hdfs haadmin -failover nn2 nn1
Failover to NameNode at ruozedata001/172.19.6.116:8020 successful

此时再次执行 get_hdfs_ha_state.sh 脚本

[hadoop@ruozedata001 hadoop]$ ./get_hdfs_ha_state.sh 
                                                                
Hostname        Namenode_Serviceid      Namenode_State
ruozedata001        nn1     active
ruozedata002        nn2     standby
send a mail # 发送邮件了

此时邮箱也已经收到了邮件预警信息