Deploying WordPress on GCP using Terraform Registry. In the previous lecture, we learned how to deploy Infrastructure as Code on Google Cloud Platform using Google Deployment Manager. I mentioned earlier that one of the benefits of Infrastructure as Code is its portability across multiple environments and providers though, and Google Deployment Manager kind of locks our application into the Google Cloud Platform.

Let's see how we can create another WordPress deployment using Terraform instead this time. In our example we'll still use Terraform to deploy to Google Cloud Platform, but Terraform also supports all other major cloud providers so we could easily move or expand our application to other hosting locations with only minimal configuration changes needed.

We'll first need to download Terraform from terraform.io, then extract it to a location on our computer. Then we'll add Terraform to our PATH in our Windows environment variables, so we can call Terraform by name from the command line. We can then confirm it's working by running terraform -version. We're already familiar with Google Deployment Manager templates, so let's explore the same concept again with Terraform. 

Terraform has its own registry for templates, or what Terraform prefers to call modules, with support for many different providers. Let's find a WordPress module on the Terraform Registry and see how we can deploy it to our GCP project. This one looks like it fits the bill. If we look at the module source code, we can see there's just one main file with our IaC code, and a variables file to separate our variable definitions from the rest of our configuration.

We could pull this repository and use it directly in our project, or we could instead create a new main.tf file and call this configuration as a module directly through the Terraform Registry. I have included an example of that in the repository for this course. All you have to do is edit the project ID and regions for your project in the main.tf file, and with just these few lines we can build our entire WordPress server with Terraform. 

Before we run Terraform though, we need to check that we have all the APIs that our deployment will need already enabled, we can do that quickly with these commands. We also need to run this gcloud command for authentication. Since we have Terraform installed locally we can use Application Default Credentials to authenticate Terraform with our own Google account, without needing to include a key file in our project.

We then need to add secrets for root_pass, database, db_user, and db_user_pass to Google Secret Manager. Our Terraform module will look for this sensitive data from Google Secret Manager, instead of storing it in our repository in plain text. Now we're ready to run terraform init, then terraform apply, and we should see Terraform start to deploy our application. This will take a few minutes to run.

Notice how Terraform adds this state file to your project in the background as it's building. Terraform manages this file on it's own and we don't need to edit it directly, however this file is very important and you'll want to make sure you're tracking it with version control. You won't be able to manage your Terraform deployments once they are deployed without this file.

The Terraform state file is used to map deployed resources to the configurations they came from, and caches metadata about deployments. This also helps improve performance when updating deployments to match detected configuration changes with Terraform. Once our Terraform deployment completes, a browser window will open for us automatically and we're greeted with a fresh WordPress site.

That concludes our last demo for this course. In our final lecture, we'll review what we've learned, and discuss some key takeaways from this course in our last few minutes together.