CloudFlare A records failover script using CloudFlare api v4 (https://api.cloudflare.com) required jq and curl to run.

cloudflare-failover.sh

#!/bin/bash
# Copyright (C) 2016 Arash Shams <https://github.com/Ara4Sh>.
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program.  If not, see <http://www.gnu.org/licenses/>.

#Setting Environment
#set -o errexit
#set -o nounset
#set -o pipefail

#CloudFlare Configs

#CloudFlare API Key : https://www.cloudflare.com/a/account/my-account
CF_KEY=
#Zone Name : example.com
CF_ZONE=
#Zone Identifier
CF_ID=
#CloudFlare Username : user@example.com
CF_USER=
#Cloudflare TTL for record, between 120 and 86400 seconds
CF_TTL=
#Domain Name to check
DOMAIN=
#IP Addresses
A_IPS=()

#Get Params
while getopts k:z:i:u:t:d:a: opts; do
	case ${opts} in
		k) CF_KEY=${OPTARG} ;;
		z) CF_ZONE=${OPTARG};;
		i) CF_ID=${OPTARG} ;;
		u) CF_USER=${OPTARG} ;;
		t) CF_TTL=${OPTARG} ;;
		d) DOMAIN=${OPTARG} ;;
		a) A_IPS+=(${OPTARG}) ;;
	esac
done

#Checking for Required Parameters
if [[ "$CF_KEY" = "" ]]; then
	echo "Missing API Key, get at https://www.cloudflare.com/a/account/my-account"
	echo "and save in ${0} or using -k flag"
	exit 2
fi
if [[ "$CF_USER" = "" ]]; then
	echo "Missing Username , its your Email address that registered in CloudFlare"
	echo "and save in ${0} or using the -u flag"
	exit 2
fi

if [[ "$CF_TTL" = "" ]]; then
	echo "Missing TTL , Choose between 120 and 86400 seconds "
	echo "Setting default TTL to 120"
	CF_TTL=120
	echo "You can specify TTL manually and save in ${0} or using the -t flag"
fi

if [[ "$CF_ZONE" = "" ]]; then
	echo "Missing Zone parameter"
	echo "Listing All Available zones (Make sure API is valid)"
	curl -s -X GET "https://api.cloudflare.com/client/v4/zones" \
		-H "X-Auth-Email: $CF_USER" \
		-H "X-Auth-Key: $CF_KEY" \
		-H "Content-Type: application/json" \
		| jq -r '.result[].name'
	echo "Please specify one of available zone in ${0} or specify using the -z flag"
	exit 2
fi

if [[ "$DOMAIN" = "" ]]; then
	echo "Missing Domain Name"
	echo "Automatically set Domain name to $CF_ZONE"
	DOMAIN=$CF_ZONE
	echo "You can specify domain name manually in ${0} or using -d flag"
fi

if [[ "$CF_ID" = "" ]]; then
	echo "Missing Zone Identifier"
	echo "Set Automatically zone Identifier"
	CF_ID=$(curl -s -X GET https://api.cloudflare.com/client/v4/zones?name=$CF_ZONE \
		-H "X-Auth-Email: $CF_USER" \
		-H "X-Auth-Key: $CF_KEY" \
		-H "Content-Type: application/json" \
		| jq -r '.result[].id')
	echo "Zone Identifier is now $CF_ID"
	if [[ -z $CF_ID ]]; then
		echo "Problem in Automaticly set CF_ID"
		echo "Please specify CF_ID in ${0} or specify using the -i flag"
	fi
fi

if [[ "${#A_IPS[@]}" -eq 0 ]]; then
    echo "Missing A Records"
    echo "Please specify A_IPS in ${0} or specify using multiple -a flag"
    echo "Listing Available A records"
    curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records?type=A&name=$DOMAIN" \
       	-H "X-Auth-Email: $CF_USER" \
	    -H "X-Auth-Key: $CF_KEY" \
	    -H "Content-Type: application/json" \
	    | jq -r '.result[].content'
	exit 2
fi

check_domains() {
	domain=$1
	check_domain=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones" \
		-H "X-Auth-Email: $CF_USER" \
		-H "X-Auth-Key: $CF_KEY" \
		-H "Content-Type: application/json" \
		| jq -r '.result[].name'\
		| grep -c $domain)
	if [[ $check_domain -eq 0 ]]; then
		echo "Error : $domain is not present in CloudFlare"
		exit 2
	fi

}

add_a_record() {
	a_record=$1
	check_a=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records?type=A&name=$DOMAIN" \
       	-H "X-Auth-Email: $CF_USER" \
    	-H "X-Auth-Key: $CF_KEY" \
    	-H "Content-Type: application/json" \
	    | jq -r '.result[].content' \
    	| grep -c $a_record)
	if [[ $check_a -eq 0 ]]; then
		curl -s -X POST "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records" \
			-H "X-Auth-Email: $CF_USER" \
			-H "X-Auth-Key: $CF_KEY" \
			-H "Content-Type: application/json" \
			--data '{"type":"A","name":"'$DOMAIN'","content":"'$a_record'","ttl":'$CF_TTL'}' > /dev/null 2>&1
	fi
}

delete_a_record() {
	a_record=$1
	REC_ID=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records?type=A&name=$DOMAIN&content=$a_record" \
			-H "X-Auth-Email: $CF_USER" \
			-H "X-Auth-Key: $CF_KEY" \
			-H "Content-Type: application/json" \
			| jq -r '.result[].id')
	curl -s -X DELETE "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records/$REC_ID" \
			-H "X-Auth-Email: $CF_USER" \
			-H "X-Auth-Key: $CF_KEY" \
			-H "Content-Type: application/json" > /dev/null 2>&1
}
#Gathering Recordst
#A_RECS=($(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$CF_ID/dns_records?type=A&name=$DOMAIN" \
#       	-H "X-Auth-Email: $CF_USER" \
#	-H "X-Auth-Key: $CF_KEY" \
#	-H "Content-Type: application/json" \
#	| jq -r '.result[].content'))

for ip in "${A_IPS[@]}"
do
	CHK_REC=$(curl -s -m 2 -I "Host: $domain" $ip | head -n1 | grep -c 200)
	if [[ $CHK_REC -eq 0 ]]; then
		delete_a_record $ip
	else
		add_a_record $ip
	fi
done