Monitors the HTTP status of a web server and sends and alert email to an administrator if the server goes down

server_status

#!/bin/bash
#
# --------------------------------------------------------------------------------------------
# Automatic Residency Wiki Web Server Status Checkup
# --------------------------------------------------------------------------------------------
# This file checks the status of the residency wiki database at 
# https://resdb.physicianscientists.org/Main_Page in order to determine if the server has gone
# down.  Basic "curl" is performed looking for HTTP 200 status code.  An email alert is sent
# to an administrator if a 200 status code is not received.
# 
# --------------------------------------------------------------------------------------------
# Author Info
# --------------------------------------------------------------------------------------------
# Name :: Tim Kennell Jr. ~ tikenn
#
# --------------------------------------------------------------------------------------------
# Config
# --------------------------------------------------------------------------------------------
# URL :: The web address of residency wiki database to check the status of
# EMAIL_FROM :: The fake email address that the system should use to send the alert
# EMAIL_TO :: The email address that the alert should be sent to
# EMAIL_SUBJECT :: The subject of the email alert
# EMAIL_BODY :: The body of the email alert
#
# --------------------------------------------------------------------------------------------
# Setting up crontab
# --------------------------------------------------------------------------------------------
# - Create a file in /etc/cron.d/
# - Suggested to run the file once a week
# - Example line (runs at midnight): "0 0 * * 1 /path/to/wiki_server_status"
#
# ~ tikenn

# Setting GLOBAL variables for the script
URL=https://resdb.physicianscientists.org/Main_Page
EMAIL_FROM=resdb@$HOSTNAME.server
EMAIL_TO=resdb@physicianscientists.org
EMAIL_SUBJECT="Residency Wiki Database Down"
EMAIL_BODY="The residency wiki server is down as of checking at $(date +"%F %T") "

# --------------------------------------------------------------------------------------------
# Core App
# --------------------------------------------------------------------------------------------

# Setting up the cron job file
cron_job_file="/etc/cron.d/wiki_server_status"

cron_job_intro="# Sets up the cron job for checking the server\n"
cron_job_intro+="# Main script at /opt/server_status\n\n"
cron_job_intro+="PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\n\n"
cron_job_schedule="0 * * * * root /opt/server_status/server_status"
cron_job_schedule_down="0 8 * * * root /opt/server_status/server_status"

if ! [[ -f "$cron_job_file" ]] ; then
	echo "cron file not created"
	printf "$cron_job_intro" > "$cron_job_file"
	printf "$cron_job_schedule" >> "$cron_job_file"
fi

# echo -e "The last cron job was run at $(date +"%F %T")\n" >> /opt/server_status/cron_job_test

# Check the status of the server for 200 status code and send alert email if 200 not returned
server_status=$(curl -sI "$URL" | head -n 1 | cut -d ' ' -f2)

if ! [[ "$server_status" = "200" ]] ; then
	EMAIL_BODY+="and is throwing a $server_status status code"

	# email error
	echo -e "$EMAIL_BODY" | \
	mutt -e "set from=$EMAIL_FROM realname='Residency Wiki Database Status Script'" \
		 -e "set crypt_use_gpgme=no" \
		 -s "$EMAIL_SUBJECT" \
		 -- "$EMAIL_TO"

	# slow down cron job to avoid email bombardment
	echo "$cron_job_intro" > "$cron_job_file"
	echo "$cron_job_schedule_down" >> "$cron_job_file"

else
	# speed up cron job if previously slowed down
	if ! [[ $(awk 'NR==6' "$cron_job_file" | cut -d' ' -f2) = '*' ]] ; then
		printf "$cron_job_intro" > "$cron_job_file"
		printf "$cron_job_schedule" >> "$cron_job_file"
	fi
fi

# ---------------------------------------------------------------------------------------------
# End of Core App
# ---------------------------------------------------------------------------------------------