Terraform
1. Terraform
So far, you have been creating Google Cloud resources using the Google Cloud console and Cloud Shell. We recommend the console when you are new to using a service or if you prefer a UI. Cloud Shell works best when you are comfortable using a specific service and you want to quickly create resources using the command line. Terraform takes this one step further. Terraform is one of the tools used for Infrastructure as Code or IaC. Before we dive into understanding Terraform, let's look at what Infrastructure as Code is. In essence, infrastructure as code allows for the quick provisioning and removing of infrastructures. The on-demand provisioning of a deployment is extremely powerful. This can be integrated into a continuous integration pipeline that smoothens the path to continuous deployment. Automated infrastructure provisioning means that the infrastructure can be provisioned on demand, and the deployment complexity is managed in code. This provides the flexibility to change infrastructure as requirements change. And all the changes are in one place. Infrastructure for environments such as development and test can now easily replicate production and can be deleted immediately when not in use. All because of infrastructure as code. Several tools can be used for IaC. Google Cloud supports Terraform, where deployments are described in a file known as a configuration. This details all the resources that should be provisioned. Configurations can be modularized using templates which allow the abstraction of resources into reusable components across deployments. In addition to Terraform, Google Cloud also provides support for other IaC tools, including: Chef Puppet Ansible Packer In this course we will focus on Terraform. Terraform lets you provision Google Cloud resources—such as virtual machines, containers, storage, and networking—with declarative configuration files. You just specify all the resources needed for your application in a declarative format and deploy your configuration. HashiCorp Configuration Language (HCL) allows for concise descriptions of resources using blocks, arguments, and expressions. This deployment can be repeated over and over with consistent results, and you can delete a whole deployment with one command or click. The benefit of a declarative approach is that it allows you to specify what the configuration should be and let the system figure out the steps to take. Instead of deploying each resource separately, you specify the set of resources which compose the application or service, allowing you to focus on the application. Unlike Cloud Shell, Terraform will deploy resources in parallel. Terraform uses the underlying APIs of each Google Cloud service to deploy your resources. This enables you to deploy almost everything we have seen so far, from instances, instance templates, and groups, to VPC networks, firewall rules, VPN tunnels, Cloud Routers, and load balancers. For a full list of supported resource types, a link to the Using Terraform with Google Cloud documentation page is included in the Course Resources. The Terraform language is the user interface to declare resources. Resources are infrastructure objects such as Compute Engine virtual machines, storage buckets, containers, or networks. A Terraform configuration is a complete document in the Terraform language that tells Terraform how to manage a given collection of infrastructure. A configuration can consist of multiple files and directories. The syntax of the Terraform language includes: Blocks that represent objects and can have zero or more labels. A block has a body that enables you to declare arguments and nested blocks. Arguments are used to assign a value to a name. An expression represents a value that can be assigned to an identifier. Terraform can be used on multiple public and private clouds. Terraform is already installed in Cloud Shell. The example Terraform configuration file shown starts with a provider block that indicates that Google Cloud is the provider. The region for the deployment is specified inside the provider block. The resource block specifies a Google Cloud Compute Engine instance, or virtual machine. The details of the instance to be created are specified inside the resource block. The output block specifies an output variable for the Terraform module. In this case, a value will be assigned to the output variable "instance_ip." Let's look at a simple example in Terraform. Before you get into the lab, let me walk you through how Terraform can be used to set up an auto mode network with an HTTP firewall rule. For this example we are going to define our infrastructure in a single file, main.tf. As our infrastructure becomes more complex we can build each element in a separate file to make the management easier. Let's start with the main.tf file. The main.tf file is where we specify the infrastructure we wish to create. It is like a blueprint for our desired state. First we define the provider. Next we define our network, setting the auto create subnetworks flag to true which will automatically create a subnetwork in each region. We also set the mtu to 1460. Next, we define our firewall. Here we are allowing TCP access to port 80 and 8080. Terraform takes this main.tf file and uses it as the specification for what to create. Once we have completed the main.tf file, we can deploy the defined infrastructure in Cloud Shell. We use the command terraform init to initialize the new Terraform configuration. We run this command in the same folder as the main.tf file. The terraform init command makes sure that the Google provider plugin is downloaded and installed in a subdirectory of the current working directory, along with various other bookkeeping files. You will see an "Initializing provider plugins" message. Terraform knows that you're running from a Google project, and it is getting Google resources. The terraform plan command performs a refresh, unless explicitly disabled, and then determines what actions are necessary to achieve the desired state specified in the configuration files. This command is a convenient way to check whether the execution plan for a set of changes matches your expectations without making any changes to real resources or to the state. The terraform apply command creates the infrastructure defined in the main.tf file. Once this command has completed you will be able to access the defined infrastructure.2. Let's practice!
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