Comparing Terraform and Azure Bicep: Which is Right for Your Azure Infrastructure?

By Samir Zorlak, Software Developer at Authority Partners

Introduction 

As organizations increasingly adopt cloud infrastructure, the need for efficient management and provisioning becomes crucial. Infrastructure as Code (IaC) has emerged as a solution enabling the automated provisioning and management of infrastructure resources. Terraform and Azure Bicep are two tools that can be used for resource management in Azure, each with its own strengths and capabilities. Both of these tools use declarative configuration files and are idempotent, meaning their execution will always lead to the same state of desired infrastructure resources. Through blog, I will compare Terraform and Azure Bicep to help you decide which tool is right for your Azure infrastructure. 

Terraform: An In-Depth Look 

Terraform, developed by HashiCorp, uses the HashiCorp Configuration Language (HCL), is a declarative language designed specifically for defining infrastructure resources and their dependencies. HCL follows a configuration file approach where users declare the desired state of the infrastructure and let Terraform handle the execution and provisioning. 

Key Features  

  • Multi-Cloud Support: Terraform is known for its multi-cloud support, allowing users to manage infrastructure across multiple cloud providers, including AWS, Azure, Google Cloud and others. This broad compatibility makes it suitable for heterogeneous environments and multi-cloud deployments. 
  • State Management: Terraform manages its state internally in a .tfstate file to track resource dependencies and ensure idempotent execution. This file is crucial for understanding the current state of your infrastructure and planning updates accurately. 
  • Modularity: Terraform supports modules, which allow you to encapsulate configurations into reusable components. This modularity enhances code reuse and simplifies complex infrastructure setups. 
  • Ecosystem and Community: Terraform boasts a mature ecosystem with a vast library of providers and modules contributed by the community. This extensive ecosystem enables support for a wide range of cloud platforms, services and third-party integrations. 

Compilation and Deployment 

Terraform does not have a single starting file; rather, all files with the .tf extension are combined to create a list of resources to be deployed. Users first run terraform plan to generate a preview of the changes, comparing the configuration with the state file, and then terraform apply to execute the provisioning. Terraform’s CLI performs all logic execution locally, making calls to management APIs to provision resources. Terraform can also destroy all created resources using the terraform destroy command. 

Additionally, Terraform performs a refresh of the state file before running plan or apply commands. If there are manual updates to the infrastructure, Terraform will recreate the resource if it was manually deleted or change it if it was manually updated. If a resource is removed from the configuration files that were previously created by Terraform, it will be deleted from the infrastructure on the next apply command. 

For deployment of infrastructure using Terraform in Azure DevOps, you will need to install the Terraform extension that provides two additional tasks, one for installing Terraform tool on agent and a second for the deployment of the Terraform configuration. This task also needs to have backend configured for storing state file and that can be Azure, AWS or GCP. In case Terraform Cloud is used, the bash script task can be used in the pipeline to execute commands for the deployment of infrastructure. 

The deployment of infrastructure for multiple environments for smaller projects can be handled using separate directories for each environment with a single configuration file that uses modules in Terraform or templates for Bicep. For more complex projects, a better solution is to use different variables or variable groups for different environments and reuse the same configuration files. This is a better approach, especially because secrets and sensitive values can be kept in KeyVault or in Azure DevOps variable groups. 

Because Terraform must have a different state file for each environment, Terraform workspaces can also be used. Each workspace has its own state file, but to avoid issues with deployment, proper switching between workspaces must not be forgotten. 

Azure Bicep: An In-Depth Look 

Azure Bicep, developed by Microsoft, adopts a syntax similar to TypeScript, providing a more expressive and concise language for defining Azure resources. It was created to simplify the complexities of ARM templates and make IaC easier using Microsoft tools. 

Key Features 

  • Azure-Native: Bicep is tightly integrated with Azure Resource Manager (ARM) and specializes in provisioning resources within the Azure ecosystem. 
  • Simplified Syntax: Bicep leverages constructs familiar to developers accustomed to JavaScript-based languages, offering features such as type safety, modularization and advanced expressions. 
  • Tooling Integration: Bicep integrates seamlessly with Azure CLI, Visual Studio Code and other Azure services, providing a streamlined development and deployment experience. 
  • Deployment Modes: Bicep supports various deployment modes such as Incremental, Complete and Validate, offering flexibility in managing Azure resources.  

Compilation and Deployment 

Deploying Bicep requires a single ‘entry’ point file, which is compiled to generate ARM templates. These templates are then deployed using standard Azure deployment mechanisms. Bicep’s CLI monitors the status of the deployment and waits for execution. Unlike Terraform, Bicep does not use a state file, relying instead on Azure’s resource management capabilities. 

Bicep’s deployment modes include:  

  • Incremental: Default mode, which creates or updates resources specified in the configuration files. 
  • Complete: Removes all resources not specified in the configuration files within the targeted resource group or subscription. 
  • Validate: Checks for issues in the configuration before actual resource creation. 

 

Similar to Terraform, Bicep will recreate a resource if it was manually deleted or update it if it was manually modified. However, unlike Terraform, Bicep will not delete resources if they are removed from the configuration files in Incremental deployment mode. In Complete deployment mode, all resources not specified in the configuration will be removed. 

For using Bicep to deploy infrastructure, the ARM template deployment task is used where deployment scope, service connection, Bicep file path and deployment mode are set. 

Managing multiple environments with Bicep typically involves using parameter files or different Bicep configurations for each environment. This approach ensures that environment-specific settings, such as resource names and configurations, are applied appropriately. 

Comparing Key Features 

Multi-Cloud vs. Azure-Specific Support 

Terraform’s multi-cloud support makes it ideal for organizations managing resources across different cloud providers. In contrast, Bicep is Azure-specific, making it a natural choice for organizations deeply integrated with the Azure ecosystem. 

Language Syntax and Developer Experience 

Terraform uses HCL, which is designed for infrastructure configurations and supports complex expressions, loops and conditionals. Bicep, with its TypeScript-like syntax, offers a more developer-friendly experience, particularly for those familiar with JavaScript-based languages. Bicep’s syntax is more concise, reducing the verbosity seen in ARM templates. 

State Management 

Terraform’s use of a state file is both a strength and a complexity. It allows precise tracking of infrastructure state but requires careful management and sharing among team members. Bicep’s stateless approach simplifies smaller projects by eliminating the need for state management, although it relies on Azure’s native capabilities for resource tracking. 

Modularity and Code Reuse 

Both tools support modularization, but Terraform’s mature ecosystem and extensive module library give it an edge in reusability and community-contributed resources. Bicep is catching up, with growing support for modules and reusable components within the Azure ecosystem. 

Pros and Cons 

Terraform 

Advantages 

Disadvantages 

  • Multi-cloud support: Versatility across different cloud environments. 
  • Mature ecosystem: Extensive community support and modules. 
  • Robust state management: Detailed tracking of infrastructure changes. 
  • Extensibility: Wide range of providers and integrations. 

 

  • State File Management: Requires careful handling to avoid conflicts and ensure consistency. 

 

 

Azure Bicep 

Advantages 

Disadvantages 

  • Azure-native integration: Seamless deployment within Azure. 
  • Simplified syntax: More concise and developer-friendly than ARM templates. 
  • Tooling integration: Excellent support within the Azure ecosystem. 
  • No State File: Simplifies management for smaller projects and teams. 

 

  • Limited to Azure: Not suitable for multi-cloud environments. 

 

Conclusion 

Both Terraform and Azure Bicep are powerful tools for managing Azure resources, each with its own strengths and weaknesses. Terraform’s multi-cloud capabilities and mature ecosystem make it suitable for diverse environments, while Azure Bicep’s simplicity and tight integration with Azure services offer a streamlined experience for Azure-centric projects. Since Bicep does not use state file, for simpler and smaller projects, Bicep can be the first choice, as there is no need to take care of sharing state between team members or refreshing state file if there are some manual updates on infrastructure. Ultimately, the choice between Terraform and Azure Bicep will depend on your specific infrastructure needs, project complexity and cloud strategy. Experiment with both tools to determine which one best fits your requirements and helps you achieve your infrastructure goals effectively. 

 

Get Expert Help with Your Next Project 

Leverage our expertise to streamline your Azure infrastructure management. Whether you’re leaning towards Terraform or Azure Bicep, our team at Authority Partners can provide the guidance and support you need. Reach out to us via our web form or email us at hello@authoritypartners.com to get started on your next project. Let’s build something great together!