Adding the new Consul Template Guide. (#4947)

* Adding the new Consul Template Guide.

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Making updates based on Pauls feedback.

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Update website/source/docs/guides/consul-template.html.md

Co-Authored-By: kaitlincarter-hc <43049322+kaitlincarter-hc@users.noreply.github.com>

* Couple more updates based on Pauls feedback.

* updated the intro to include how template can replace api use

* updated the address

* Adding minikube guide to the index page.

website/source/docs/guides/consul-template.html.md

@@ -0,0 +1,188 @@
+---
+layout: "docs"
+page_title: "Consul Template"
+sidebar_current: "docs-guides-consul-template"
+description: |-
+  Consul template provides a programmatic method for rendering configuration files from Consul data.
+---
+
+# Consul Template
+
+The Consul template tool provides a programmatic method 
+for rendering configuration files from a variety of locations,
+including Consul KV. It is an ideal option for replacing complicated API 
+queries that often require custom formatting.
+The template tool is based on Go templates and shares many 
+of the same attributes. 
+
+Consul template is a useful tool with several uses, we will focus on two
+of it's use cases.
+
+1. *Update configuration files*. The Consul template tool can be used
+to update service configuration files. A common use case is managing load 
+balancer configuration files that need to be updated regularly in a dynamic 
+infrastructure on machines many not be able to directly connect to the Consul cluster. 
+
+1. *Discover data about the Consul cluster and service*. It is possible to collect 
+information about the services in your Consul cluster. For example, you could 
+collect a list of all services running on the cluster or you could discover all 
+service addresses for the Redis service. Note, this use case has limited 
+scope for production. 
+
+In this guide we will briefly discuss how `consul-template` works, 
+how to install it, and two use cases. 
+
+Before completing this guide, we assume some familiarity with 
+[Consul KV](https://learn.hashicorp.com/consul/getting-started/kv.html)
+ and [Go templates](https://golang.org/pkg/text/template/).
+
+## Introduction to Consul Template 
+
+Consul template is a simple, yet powerful tool. When initiated, it 
+reads one or more template files and queries Consul for all 
+data needed to render them. Typically, you run `consul-template` as a 
+daemon which will fetch the initial values and then continue to watch 
+for updates, re-rendering the template whenever there are relevant changes in 
+the cluster. You can alternatively use the `-once` flag to fetch and render 
+the template once which is useful for testing and
+setup scripts that are triggered by some other automation for example a 
+provisioning tool. Finally, the template can also run arbitrary commands after the update 
+process completes. For example, it can send the HUP signal to the 
+load balancer service after a configuration change has been made. 
+
+The Consul template tool is flexible, it can fit into many
+different environments and workflows. Depending on the use-case, you 
+may have a single `consul-template` instance on a handful of hosts 
+or may need to run several instances on every host. Each `consul-template` 
+process can manage multiple unrelated files though and will de-duplicate
+ the fetches as needed if those files share data dependencies so it can 
+reduce the load on Consul servers to share where possible.
+
+## Install Consul Template
+
+For this guide, we are using a local Consul agent in development
+mode which can be started with `consul agent -dev`. To quickly set 
+up a local Consul agent, refer to the getting started [guide](https://learn.hashicorp.com/consul/getting-started/install). The 
+Consul agent must be running to complete all of the following
+steps. 
+
+The Consul template tool is not included with the Consul binary and will
+need to be installed separately. It can be installed from a precompiled 
+binary or compiled from source. We will be installing the precompiled binary.
+
+First, download the binary from the [Consul Template releases page](https://releases.hashicorp.com/consul-template/).
+
+```sh
+curl -O https://releases.hashicorp.com/consul-template/0.19.5/consul-template<_version_OS>.tgz
+```
+
+Next, extract the binary and move it into you `$PATH`.
+
+```sh
+tar -zxf consul-template<_version_OS>.tgz
+``` 
+
+To compile from source, please see the instructions in the
+[contributing section in Github](https://github.com/hashicorp/consul-template#contributing).
+
+## Use Case: Consul KV
+
+In this first use case example, we will render a template that pulls the HashiCorp address
+from Consul KV. To do this we will create a simple template that contains the HashiCorp
+address, run `consul-template`, add a value to Consul KV for HashiCorp's address, and 
+finally view the rendered file.   
+
+First, we will need to create a template file `find_address.tpl` to query 
+Consul's KV store:
+
+```liquid
+{{ key "/hashicorp/street_address" }}
+```
+
+Next, we will run `consul-template` specifying both
+the template to use and the file to update. 
+
+```shell
+$ consul-template -template "find_address.tpl:hashicorp_address.txt" 
+```
+
+The `consul-template` process will continue to run until you kill it with `CRTL+c`. 
+For now, we will leave it running. 
+
+Finally, open a new terminal so we can write data to the key in Consul using the command 
+line interface.
+
+```shell
+$ consul kv put hashicorp/street_address "101 2nd St"
+$ Success! Data written to: hashicorp/street_address
+```
+
+We can ensure the data was written by viewing the `hashicorp_address.txt`
+file which will be located in the same directory where `consul-template`
+was run.
+
+```shell
+$ cat hashicorp_address.txt
+101 2nd St
+```
+
+If you update the key `hashicorp/street_address`, you can see the changes to the file 
+immediately. Go ahead and try `consul kv put hashicorp/street_address "22b Baker ST"`.
+
+You can see that this simple process can have powerful implications. For example, it is
+possible to use this same process for updating your [HAProxy load balancer 
+configuration](https://github.com/hashicorp/consul-template/blob/master/examples/haproxy.md). 
+
+You can now kill the `consul-template` process with `CTRL+c`. 
+
+## Use Case: Discover All Services
+
+In this use case example, we will discover all the services running in the Consul cluster. 
+To follow along, you use the local development agent from the previous example.
+
+First, we will need to create a new template `all-services.tpl` to query all services.
+
+```liquid
+{{range services}}# {{.Name}}{{range service .Name}}
+{{.Address}}{{end}}
+
+{{end}}
+```
+
+Next, run Consul template specifying the template we just created and the `-once` flag.
+The `-once` flag will tell the process to run once and then quit. 
+
+```shell
+$ consul-template -template="all-services.tpl:all-services.txt" -once
+```
+
+If you complete this on your local development agent, you should
+still see the `consul` service when viewing `all-services.txt`.
+
+```text
+# consul
+127.0.0.7
+```
+On a development or production cluster, you would see a list of all the services. 
+For example:
+
+```text
+# consul
+104.131.121.232
+
+# redis
+104.131.86.92
+104.131.109.224
+104.131.59.59
+
+# web
+104.131.86.92
+104.131.109.224
+104.131.59.59
+```
+
+## Conclusion
+
+In this guide we learned how to set up and use the Consul template tool.
+To see additional examples, refer to the examples folder 
+in [github](https://github.com/hashicorp/consul-template/tree/master/examples).

website/source/docs/guides/index.html.md

@@ -28,6 +28,8 @@ The following guides are available:
 
 * [Consul with Containers](/docs/guides/consul-containers.html) - This guide describes critical aspects of operating a Consul cluster that's run inside containers.
 
+* [Consul Template](/docs/guides/consul-template.html) - This guide covers the Consul template tool, which provides a programmatic method for populating values into the file system.
+
 * [Creating Certificates](/docs/guides/creating-certificates.html) - This guide describes how to setup CA and certificates to secure a Consul cluster with TLS.
 
 * [Deployment Guide](/docs/guides/deployment-guide.html) - This deployment guide covers the steps required to install and configure a single HashiCorp Consul cluster as defined in the Consul Reference Architecture.
@@ -42,6 +44,8 @@ The following guides are available:
 
 * [Geo Failover](/docs/guides/geo-failover.html) - This guide covers using [prepared queries](/api/query.html) to implement geo failover for services.
 
+* [Minikube with Consul](/docs/guides/minikube.html) - In this guide, you'll start a local Kubernetes cluster with minikube, install Consul,and then deploy two custom services.
+
 * [Leader Election](/docs/guides/leader-election.html) - The goal of this guide is to cover how to build client-side leader election using Consul.
 
 * [Monitoring Consul with Telegraf](/docs/guides/monitoring-telegraf.html) - This guide demonstrates how to setup Consul for monitoring with Telegraf.
@@ -58,4 +62,4 @@ The following guides are available:
 
 * [Server Performance](/docs/guides/performance.html) - This guide covers minimum requirements for Consul servers as well as guidelines for running Consul servers in production.
 
-* [Windows Service](/docs/guides/windows-guide.html) - This guide covers how to run Consul as a service on Windows.
+* [Windows Service](/docs/guides/windows-guide.html) - This guide covers how to run Consul as a service on Windows.

website/source/layouts/docs.erb

@@ -402,6 +402,9 @@
           <li<%= sidebar_current("docs-guides-consul-containers") %>>
             <a href="/docs/guides/consul-containers.html">Consul with Containers</a>
           </li>
+          <li<%= sidebar_current("docs-guides-consul-template") %>>
+            <a href="/docs/guides/consul-template.html">Consul Template</a>
+          </li>
           <li<%= sidebar_current("docs-guides-creating-certificates") %>>
             <a href="/docs/guides/creating-certificates.html">Creating Certificates</a>
           </li>