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Infrastructure as Code (IaC) tools: ARM, Bicep & Terraform

It's important to choose the IAC tool that suits your team’s needs best. There is no silver bullet and it’s nice to have choices. In this article, we discuss the benefits and features of each tool based on our own experiences.

Reading time 5 minutes. Published: 28 March 2024

ARM Templates: The Foundation of Azure IaC

ARM templates are the foundational technology for Infrastructure as Code (IaC) in Azure. They are JSON files that declaratively define the resources needed for an Azure application. ARM templates provide a comprehensive approach to infrastructure management, allowing for the definition of dependencies between resources, complex configurations, and advanced deployment scenarios.

Despite their power, ARM templates can be pretty daunting, due to their verbose and complex syntax. This complexity makes it a challenging tool, especially for those new to IaC or Azure. However, for complex deployments that require granular control over resources, ARM templates offer unparalleled flexibility and depth. 

Most of the time at Intercept we tend not to use ARM templates. We mostly use Bicep for Azure deployments.

Bicep: The Native Azure IaC Language

Bicep stands out as Azure's native Infrastructure as Code (IaC) language, designed to simplify the authoring of Azure resources. Bicep's declarative syntax allows us to define what Azure resources are needed without detailing how to create them. This focus on simplicity makes Bicep an attractive option for those deeply embedded in the creation of Azure resources.

Bicep files compile down to ARM templates, ensuring full compatibility with Azure's deployment and management services. This seamless integration with Azure means that any resource available in Azure can be defined using Bicep. 

Moreover, Bicep's tooling is integrated into Azure CLI and PowerShell, making it an integral part of the Azure development experience. Most of us at Intercept use Visual Studio Code. With the Bicep extension installed, we get code completion: a visualizer that helps you see what your script will deploy. Additionally, we make use of a simple PowerShell template for calling our scripts.

Terraform: A Cross-Platform IaC Solution

Terraform (by HashiCorp) is a popular open-source tool that enables Infrastructure as Code (IaC) across multiple cloud providers, including Azure. Unlike Bicep and ARM templates, which are specific to Azure, Terraform provides a single workflow to manage resources across various Clouds and services. This makes Terraform an ideal choice for organizations with multi-cloud environments or those looking to avoid vendor lock-in.

Terraform uses its own declarative configuration language, HCL (HashiCorp Configuration Language), to define resources. It maintains state files to keep track of the resources it manages, enabling safe and efficient updates to infrastructure with minimal manual intervention.

ARM Templates, Bicep or Terraform?

The choice between ARM templates, Bicep, and Terraform depends on several factors, such as the specific requirements of the project, the team's familiarity with the tools, and the broader IT environment of the organization.

ARM templates are the go-to option for complex Azure deployments that require the full breadth of features and control offered by Azure. They are ideal for users who need fine-grained control over their infrastructure and are willing to navigate the complexity of ARM's JSON syntax.

Bicep is best suited for teams that are committed to the Azure platform and value simplicity and readability in their IaC scripts. Its tight integration with Azure makes it an excellent choice for purely Azure-centric projects.

Terraform stands out for environments that span multiple cloud providers or where there is a need to standardize IaC practices across different platforms. Its broader ecosystem and community support can also be beneficial for complex deployments.

Infrastructure as Code: what tool do I choose?

Infrastructure as Code has become an indispensable practice in cloud computing, offering speed, efficiency, and reliability in infrastructure provisioning and management. In the Azure context, ARM templates, Bicep, and Terraform each provide unique benefits tailored to different needs and preferences. 

ARM templates offer deep customization for complex environments. Bicep simplifies Azure-specific deployments with its accessible syntax. And Terraform provides a versatile toolset for multi-cloud strategies. Understanding the strengths and limitations of each tool is key to leveraging IaC effectively within Azure and beyond, ensuring robust, scalable, and maintainable infrastructure for modern applications.

Maria Tom

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