Infrastructure as Code (IaC): Azure Resource Manager Templates vs. Bicep

Infrastructure as Code (IaC) has become a cornerstone of modern DevOps practices, enabling teams to provision and manage cloud infrastructure through code. In the Azure ecosystem, two primary tools for implementing IaC are Azure Resource Manager (ARM) templates and Bicep. While both serve similar purposes, they differ significantly in syntax, usability, and functionality. This blog will compare these tools to help you decide which one to use for your Azure infrastructure needs.

Azure Resource Manager Templates

ARM templates have been the backbone of Azure IaC for many years. Written in JSON, they define the infrastructure and configuration for Azure resources declaratively.

Key Features:

1. Declarative Syntax: ARM templates use a JSON format to describe the desired state of your infrastructure.
2. Robust Tooling: Supported natively in the Azure portal, Azure CLI, and Azure PowerShell.
3. Comprehensive Resource Support: Fully supports all Azure resources and their properties.

Advantages:

• Mature Ecosystem: Well-documented with extensive community support.
• Integrated Deployment: Directly integrated into Azure DevOps and other CI/CD pipelines.
• Extensibility: Supports advanced features like linked templates and nested deployments.

Challenges:

• Verbose Syntax: JSON can become unwieldy and difficult to maintain for large templates.
• Limited Modularity: Reusability and parameterization can be cumbersome.

Bicep

Bicep is a domain-specific language (DSL) introduced by Microsoft to simplify the authoring of Azure IaC. It is designed as a more user-friendly alternative to ARM templates.

Key Features:

1. Simplified Syntax: Uses a concise, YAML-like syntax that is easier to read and write.
2. First-Class Azure Integration: Fully supports all Azure resources and integrates seamlessly with ARM.
3. Built-in Validation: Provides real-time feedback and validation during development.

Advantages:

• Readable and Maintainable: Significantly reduces boilerplate code compared to JSON.
• Modular Design: Encourages the reuse of code through modules.
• No Compilation Required: Automatically transpiles to ARM templates for deployment.
• Frequent Updates: Rapidly evolving with features like loops, conditionals, and resource dependencies.

Challenges:

• Learning Curve: Requires familiarity with a new language, albeit simpler than JSON.
• Early-Stage Tooling: While improving, it’s still newer than ARM templates, so tooling and community resources are evolving.

Comparing ARM Templates and Bicep

When to Use ARM Templates

ARM templates remain a solid choice for:

• Teams with existing investments in JSON-based IaC.
• Scenarios requiring advanced, linked templates for complex deployments.
• Organizations that prioritize long-term support and documentation.

When to Use Bicep

Bicep is ideal for:

• New projects requiring IaC in Azure.
• Teams seeking a more developer-friendly experience.
• Scenarios that benefit from modular and reusable code.

To conclude, both ARM templates and Bicep are powerful tools for managing Azure resources through IaC. ARM templates offer a mature, battle-tested approach, while Bicep provides a modern, streamlined experience. For teams new to Azure IaC, Bicep’s simplicity and modularity make it a compelling choice. However, existing users of ARM templates may find value in sticking with their current workflows or transitioning gradually to Bicep.

Regardless of your choice, both tools are fully supported by Azure, ensuring that you can reliably manage your infrastructure in a consistent and scalable manner. Evaluate your team’s needs, skills, and project requirements to make the best decision for your IaC strategy.

We hope you found this blog useful, and if you would like to discuss anything, you can reach out to us at transform@cloudfonts.com.