The release pipeline deploys software to a target environment. But it isn't only the software that will be deployed with the release pipeline.
If you focus on Continuous Delivery, Infrastructure as Code and spinning up Infrastructure as part of your release pipeline are essential.
When we focus on the deployment of the Infrastructure, we should first consider the differences between the target environments that we can deploy to:
- On-Premises servers.
- Cloud servers or Infrastructure as a Service (IaaS). For example, Virtual machines or networks.
- Platform as a Service (PaaS) and Functions as a Service (FaaS). For example, Azure SQL Database in both PaaS and serverless options.
- Clusters.
- Service Connections.
Let us dive a bit further into these different target environments and connections.
On-premises servers
In most cases, when you deploy to an on-premises server, the hardware and the operating system are already in place. The server is already there and ready.
In some cases, empty, but most of the time not. In this case, the release pipeline can only focus on deploying the application.
You might want to start or stop a virtual machine (Hyper-V or VMware).
The scripts you use to start or stop the on-premises servers should be part of your source control and delivered to your release pipeline as a build artifact.
Using a task in the release pipeline, you can run the script that starts or stops the servers.
To take it one step further and configure the server, you should look at technologies like PowerShell Desired State Configuration(DSC).
The product will maintain your server and keep it in a particular state. When the server changes its state, you can recover the changed configuration to the original configuration.
Integrating a tool like PowerShell DSC into the release pipeline is no different from any other task you add.
Infrastructure as a service
When you use the cloud as your target environment, things change slightly. Some organizations lift and shift from their on-premises server to cloud servers.
Then your deployment works the same as an on-premises server. But when you use the cloud to provide you with Infrastructure as a Service (IaaS), you can use the power of the cloud to start and create servers when needed.
It's where Infrastructure as Code (IaC) starts playing a significant role.
Creating a script or template can make a server or other infrastructural components like a SQL server, a network, or an IP address.
By defining a template or using a command line and saving it in a script file, you can use that file in your release pipeline tasks to execute it on your target cloud.
The server (or another component) will be created as part of your pipeline. After that, you can run the steps to deploy the software.
Technologies like Azure Resource Manager are great for creating Infrastructure on demand.
Platform as a Service
When you move from Infrastructure as a Service (IaaS) to Platform as a Service (PaaS), you'll get the Infrastructure from the cloud you're running on.
For example: In Azure, you can choose to create a Web application. The cloud arranges the server, the hardware, the network, the public IP address, the storage account, and even the webserver.
The user only needs to take care of the web application that will run on this Platform.
You only need to provide the templates that instruct the cloud to create a WebApp. The same goes for Functions as a Service(FaaS) or Serverless technologies.
In Azure, it's called Azure Functions. You only deploy your application, and the cloud takes care of the rest. However, you must instruct the Platform (the cloud) to create a placeholder where your application can be hosted.
You can define this template in Azure Resource Manager. You can use the Azure CLI or command-line tools.
In all cases, the Infrastructure is defined in a script file and live alongside the application code in source control.
Clusters
Finally, you can deploy your software to a cluster. A cluster is a group of servers that work together to host high-scale applications.
When you run a cluster as Infrastructure as a Service, you need to create and maintain the cluster. It means that you need to provide the templates to create a cluster.
You also need to ensure that you roll out updates, bug fixes, and patches to your cluster. It's comparable with Infrastructure as a Service.
When you use a hosted cluster, you should consider it a Platform as a Service. You instruct the cloud to create the cluster, and you deploy your software to the cluster.
When you run a container cluster, you can use the container cluster technologies like AKS.
Service connections
When a pipeline needs access to resources, you'll often need to create service connections.
Summary
Whatever the technology you choose to host your application, your Infrastructure's creation or configuration should be part of your release pipeline and source control repository.
Infrastructure as Code is a fundamental part of Continuous Delivery and gives you the freedom to create servers and environments on-demand.
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