consul cluster

terraform module

resource "aws_security_group" "consul_server" {
    name = "consul-server-security-group"
    description = "Consul internal traffic + maintenance."

    // These are for internal traffic
    ingress {
        from_port = 0
        to_port = 65535
        protocol = "tcp"
        self = true
    }

    ingress {
        from_port = 0
        to_port = 65535
        protocol = "udp"
        self = true
    }

    // These are for maintenance
    ingress {
        from_port = 22
        to_port = 22
        protocol = "tcp"
        cidr_blocks = ["0.0.0.0/0"]
    }

    // This is for outbound internet access
    egress {
        from_port = 0
        to_port = 0
        protocol = "-1"
        cidr_blocks = ["0.0.0.0/0"]
    }
}

resource "template_file" "user_data" {
    template = "${file("${path.module}/user_data.sh")}"
    vars {
        consul_server_1 = "${var.consul_domain_name_one}"
        consul_server_2 = "${var.consul_domain_name_two}"
        consul_server_3 = "${var.consul_domain_name_three}"
    }
}

resource "aws_instance" "consul_server_one" {
    ami = "${var.ami}"
    instance_type = "${var.instance_type}"
    key_name = "${var.key_name}"
    
    tags { Name = "consul-server-one" } 
    security_groups = ["${aws_security_group.consul_server.name}"]
    user_data = "${template_file.user_data.rendered}"
}

resource "aws_instance" "consul_server_two" {
    ami = "${var.ami}"
    instance_type = "${var.instance_type}"
    key_name = "${var.key_name}"
    
    tags { Name = "consul-server-two" } 
    security_groups = ["${aws_security_group.consul_server.name}"]
    user_data = "${template_file.user_data.rendered}"
}

resource "aws_instance" "consul_server_three" {
    ami = "${var.ami}"
    instance_type = "${var.instance_type}"
    key_name = "${var.key_name}"
    
    tags { Name = "consul-server-three" } 
    security_groups = ["${aws_security_group.consul_server.name}"]
    user_data = "${template_file.user_data.rendered}"
}

resource "aws_route53_record" "consul_server_one" {
  zone_id = "Z3820KW3201KHJ"
  name = "${var.consul_domain_name_one}"
  type = "A"
  ttl = "300"
  records = ["${aws_instance.consul_server_one.private_ip}"]
}

resource "aws_route53_record" "consul_server_two" {
  zone_id = "Z3820KW3201KHJ"
  name = "${var.consul_domain_name_two}"
  type = "A"
  ttl = "300"
  records = ["${aws_instance.consul_server_two.private_ip}"]
}

resource "aws_route53_record" "consul_server_three" {
  zone_id = "Z3820KW3201KHJ"
  name = "${var.consul_domain_name_three}"
  type = "A"
  ttl = "300"
  records = ["${aws_instance.consul_server_three.private_ip}"]
}

user_data.sh

# Set necessary constants
bootstrap_expect=3

# Obtain the ip address for this host.
host_ip=$(ifconfig eth0 | grep "inet addr" | awk '{split($2,a,":"); print a[2]}')

# Pull the consul image from Docker Hub (https://hub.docker.com/_/consul/)
sudo docker pull consul

# Create a consul server container binding port 8500
sudo docker run -d --name consul \
-p $host_ip:8500:8500 \
-e 'CONSUL_LOCAL_CONFIG={"skip_leave_on_interrupt": true}' \
consul agent \
-server \
-ui \
-client=0.0.0.0 \
-bootstrap-expect $bootstrap_expect 
-advertise $host_ip \
-join ${consul_server_1} \
-join ${consul_server_2} \
-join ${consul_server_3} \
-retry-join ${consul_server_1} \
-retry-join ${consul_server_2} \
-retry-join ${consul_server_3} \