website: Consul example

website/source/intro/examples/consul.html.markdown

@@ -6,10 +6,116 @@ sidebar_current: "examples-consul"
 
 # Consul Example
 
-Words to introduce.
+[Consul](http://www.consul.io) is a tool for service discovery, configuration
+and orchestration. The Key/Value store it provides is often used to store
+application configuration and information about the infrastructure necessary
+to process requests.
+
+Terraform provides a [Consul provider](/docs/providers/consul/index.html) which
+can be used to interface with Consul from inside a Terraform configuration.
+
+For our example, we use the [Consul demo cluster](http://demo.consul.io)
+to both read configuration and store information about a newly created EC2 instance.
+The size of the EC2 instance will be determind by the "tf\_test/size" key in Consul,
+and will default to "m1.small" if that key does not exist. Once the instance is created
+the "tf\_test/id" and "tf\_test/public\_dns" keys will be set with the computed
+values for the instance.
+
+Before we run the example, use the [Web UI](http://demo.consul.io/ui/#/nyc1/kv/)
+to set the "tf\_test/size" key to "t1.micro". Once that is done,
+copy the configuration into a configuration file ("consul.tf" works fine).
+Either provide the AWS credentials as a default value in the configuration
+or invoke `apply` with the appropriate variables set.
+
+Once the `apply` has completed, we can see the keys in Consul by
+visiting the [Web UI](http://demo.consul.io/ui/#/nyc1/kv/). We can see
+that the "tf\_test/id" and "tf\_test/public\_dns" values have been
+set.
+
+We can now teardown the infrastructure following the
+[instructions here](/intro/getting-started/destroy.html). Because
+we set the 'delete' property of two of the Consul keys, Terraform
+will cleanup those keys on destroy. We can verify this by using
+the Web UI.
+
+The point of this example is to show that Consul can be used with
+Terraform both to enable dynamic inputs, but to also store outputs.
+
+Inputs like AMI name, security groups, puppet roles, bootstrap scripts,
+etc can all be loaded from Consul. This allows the specifics of an
+infrastructure to be decoupled from it's overall architecture. This enables
+details to be changed without updating the Terraform configuration.
+
+Outputs from Terraform can also be easily stored in Consul. One powerful
+features this enables is using Consul for inventory management. If an
+application relies on ELB for routing, Terraform can update the application's
+configuration directly by setting the ELB address into Consul. Any resource
+attribute can be stored in Consul, allowing an operator to capture anything
+useful.
 
 ## Configuration
 
 ```
-FOOBAR
+# Declare our variables, require access and secret keys
+variable "aws_access_key" {}
+variable "aws_secret_key" {}
+variable "aws_region" {
+    default = "us-east-1"
+}
+
+# AMI's from http://cloud-images.ubuntu.com/locator/ec2/
+variable "aws_amis" {
+    default = {
+        "eu-west-1": "ami-b1cf19c6",
+        "us-east-1": "ami-de7ab6b6",
+        "us-west-1": "ami-3f75767a",
+        "us-west-2": "ami-21f78e11",
+    }
+}
+
+# Setup the Consul provisioner to use the demo cluster
+provider "consul" {
+    address = "demo.consul.io:80"
+    datacenter = "nyc1"
+}
+
+# Setup an AWS provider
+provider "aws" {
+    access_key = "${var.aws_access_key}"
+    secret_key = "${var.aws_secret_key}"
+    region = "${var.aws_region}"
+}
+
+# Setup a key in Consul to provide inputs
+resource "consul_keys" "input" {
+    key {
+        name = "size"
+        path = "tf_test/size"
+        default = "m1.small"
+    }
+}
+
+# Setup a new AWS instance using a dynamic ami and
+# instance type
+resource "aws_instance" "test" {
+    ami = "${lookup(var.aws_amis, var.aws_region)}"
+    instance_type = "${consul_keys.input.var.size}"
+}
+
+# Setup a key in Consul to store the instance id and
+# the DNS name of the instance
+resource "consul_keys" "test" {
+    key {
+        name = "id"
+        path = "tf_test/id"
+        value = "${aws_instance.test.id}"
+        delete = true
+    }
+    key {
+        name = "address"
+        path = "tf_test/public_dns"
+        value = "${aws_instance.test.public_dns}"
+        delete = true
+    }
+}
 ```