The following shell script can be used to monitor Elasticsearch servers. The basic idea is that the server (IP:9200) will respond with a color code(Green, Red and Yellow). We use the color code to know the status of the server and notify the users through configured E-Mail addresses. An E-Mail will be sent to configured E-Mail addresses when the Elasticsearch server goes down i.e. when the status goes red.

Steps to Configure the Shell Script:

1. Copy the shell script content to a file and name it with extension .sh
2. Add the required IP addresses of the Elasticsearch servers
3. Add the hostnames(used for display purpose only) of the Elasticsearch servers
4. Add the required E-Mail addresses
5. Configure the sleep interval which is used by the script to check the status of the servers for each n minutes. Default value is 10m which represents 10minutes
6. Start the script using the command sh filename.sh or ./filename.sh (in Linux/Unix OS)

Shell Script:

#!/bin/sh

#Configure the IP addresses
IP=("IP1" "IP2" "IP3")

#Configure the hostnames
hostname=("HOSTNAME1" "HOSTNAME2" "HOSTNAME3")

while true
do
   message=""
   flag=0
   for (( i=0; i < ${#IP[@]}; i++ ))
   do
      echo $i
      response=$(curl ${IP[$i]}:9200/_cluster/health)
      if [[ ! "$response" =~ "green" ]]; then
      flag=1
         if [[ "$response" =~ "red" ]]; 
         then
            message+="Elasticsearch Server ${hostname[$i]}(${IP[$i]}) is down\n"
         elif [[ "$response" =~ "yellow" ]]; then
            message+="Elasticsearch  server ${hostname[$i]}(${IP[$i]}) shards are allocating\n"
         elif [[ "$response" == "" ]]; then
            message+="Elasticsearch process is not running in ${hostname[$i]}(${IP[$i]})\n"
         fi
      fi
   done

   if [ $flag == 1 ]; then
      echo "Sending Mail"

      #Configure the E-Mail addresses
      echo $message | mail -s "Pulse - Elasticssearch Server Down" EMailID1 EMailID2
      echo $message
   fi

   #Time duration between the monitoring. 10m represents 10 minutes
   sleep 10m
done

           The above shell script was tested and works fine in Red Hat Linux and it should also work in Unix based systems. Make sure to enable the mail settings in the system.

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