From 9be4640d67f0afffb1fbd0fb5dbaa0b18ab647e1 Mon Sep 17 00:00:00 2001
From: Steven Allen <steven.allen@heed.io>
Date: Wed, 24 Apr 2019 09:18:52 +0100
Subject: [PATCH] Initial commit of script

---
 README.md                 |   2 +-
 auto-assign-elastic-ip.sh | 100 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 auto-assign-elastic-ip.sh

diff --git a/README.md b/README.md
index 744ca21..ee5fdfd 100644
--- a/README.md
+++ b/README.md
@@ -1 +1 @@
-# aws-scripts
+# Auto Assign Elastic IP
diff --git a/auto-assign-elastic-ip.sh b/auto-assign-elastic-ip.sh
new file mode 100644
index 0000000..133ec79
--- /dev/null
+++ b/auto-assign-elastic-ip.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+
+TIMEOUT=20
+PAUSE=5
+
+aws_get_instance_id() {
+	instance_id=$( (curl http://169.254.169.254/latest/meta-data/instance-id) )
+	if [ -n "$instance_id" ];	then return 0; else return 1; fi
+}
+
+aws_get_instance_region() {
+	instance_region=$(curl http://169.254.169.254/latest/meta-data/placement/availability-zone)
+	# region here needs the last character removed to work
+	instance_region=${instance_region::-1}
+	if [ -n "$instance_region" ];	then return 0; else return 1; fi
+}
+
+aws_get_instance_environment() {
+	instance_environment=$(aws ec2 describe-tags --region $instance_region --filters "Name=resource-id,Values=$1" "Name=key,Values=Environment" --query "Tags[*].Value" --output text)
+	if [ -n "$instance_environment" ]; then return 0; else return 1; fi
+}
+
+aws_get_unassigned_eips() {
+	local describe_addreses_response=$(aws ec2 describe-addresses --region $instance_region --filters "Name=tag:Environment,Values=$instance_environment" --query "Addresses[?AssociationId==null].AllocationId" --output text)
+	eips=(${describe_addreses_response///})
+	if [ -n "$describe_addreses_response" ]; then return 0; else return 1; fi
+}
+
+aws_get_details() {
+	if aws_get_instance_id;	then
+		echo "Instance ID: ${instance_id}."
+		if aws_get_instance_region;	then
+			echo "Instance Region: ${instance_region}."
+			if aws_get_instance_environment $instance_id;	then
+				echo "Instance Environment: ${instance_environment}."
+			else
+				echo "Failed to get Instance Environment. ${instance_environment}."
+				return 1
+			fi
+		else
+			echo "Failed to get Instance Region. ${instance_region}."
+			return 1
+		fi
+	else
+		echo "Failed to get Instance ID. ${instance_id}."
+		return 1
+	fi
+}
+
+attempt_to_assign_eip() {
+	local result;
+	local exit_code;
+  	result=$( (aws ec2 associate-address --region $instance_region --instance-id $instance_id --allocation-id $1 --no-allow-reassociation) 2>&1 )
+	exit_code=$?
+	if ! exit_code; then
+		echo "Failed to assign Elastic IP [$1] to Instance [$instance_id]. ERROR: $result"
+	fi
+  return $exit_code
+}
+
+try_to_assign() {
+	local last_result;
+	for eip_id in "${eips[@]}"; do
+		echo "Attempting to assign Elastic IP to instance..."
+		if attempt_to_assign_eip $eip_id;  then
+			echo "Elastic IP successfully assigned to instance."
+			return 0
+		fi
+	done
+	return 1
+}
+
+main() {
+	echo "Assigning Elastic IP..."
+	local end_time=$((SECONDS+TIMEOUT))
+	echo "Timeout: ${end_time}"
+
+	if ! aws_get_details; then
+		exit 1
+	fi
+
+	while [ $SECONDS -lt $end_time ]; do
+		if aws_get_unassigned_eips && try_to_assign ${eips}; then
+			echo "Successfully assigned EIP."
+			exit 0
+		fi
+		echo "Failed to assign EIP. Pausing for $PAUSE seconds before retrying..."
+		sleep $PAUSE
+	done
+
+	echo "Failed to assign Elastic IP after $TIMEOUT seconds. Exiting."
+	exit 1
+}
+
+declare instance_id
+declare instance_region
+declare instance_environment
+declare eips
+
+main "$@"