Pulumi and Terraform are two top-of-the-line Infrastructure as Code (IaC) tools in the cloud engineering ecosystem. In this post, we’ll look to settle the Pulumi vs. Terraform debate to help users choose the right platform to boost cloud productivity and reduce infrastructure provisioning costs.
IaC is a critical DevOps practice used to automate the provisioning and configuration of cloud infrastructure resources, including virtual machines, load balancers, storage, networking, or any cloud resources you could ever imagine. It uses a descriptive coding approach similar to writing codes for building applications.
Table of Contents
- What is the Importance of IaC Tools
- What is Pulumi?
- What is Terraform?
- Pulumi vs Terraform: The Similarities
- Pulumi vs Terraform: 10 Key Differences
What is the Importance of IaC Tools?
Cloud Computing adaptability is increasing rapidly. In fact, the global cloud computing market size is expected to grow to $947.3 billion by 2026, compared to $445.3 billion in 2021. For this reason, enterprises are looking for solutions to automate their cloud workflows to save valuable time and reduce human dependencies that lead to infrastructure configuration errors. IaC tools offer consistent cloud infrastructure across teams, departments, and organizations.
What is Pulumi?
Pulumi is a reliable open-source Infrastructure as Code tool used for building, deploying, provisioning, and managing cloud infrastructure and applications. In the process, it promotes greater team collaboration while reducing modern cloud complexity.
Pulumi offers developer-friendly support for more than 60 cloud providers. It uses standard programming languages like Python, Node.js, .NET, and Go, which further reduces complexity compared to domain-specific languages (DSL).
Pulumi’s architecture uses a state model to manage infrastructure, which consists of three main components:
- Language Hosts: Contains a language executor and language runtime.
- Deployment Engine: Drives the state change mechanism in Pulumi.
- Resource Providers: Contains a resource plugin and SDK.
The language host executes a Pulumi program to initialize the state model. The deployment engine compares new and old state models to determine whether resources will be created, updated, or deleted. Lastly, the resource providers manage individual cloud resources from various cloud providers.
What is Terraform?
Hashicorp’s Terraform automates infrastructure provisioning and management for almost any cloud provider or service. It is an open-source IaC tool that offers infrastructure delivery as declarative configuration files written using HashiCorp’s Configuration Language (HCL).
Terraform can provision low-level cloud and on-prem components like networking, storage, compute, and high-level components like SaaS features and DNS entries. Furthermore, Terraform connects with virtually any cloud platform using more than 2000+ Terraform Providers that allow it to create and manage resources through the relevant cloud platform’s API.
Essentially, Terraform’s workflow consists of three main components:
- Write: Define your required cloud resources in configuration files
- Plan: Terraform will work on an execution plan to provision infrastructure resources defined in the configuration file
- Apply: Terraform provisions the required cloud resources
Check out our blog post that covers how to integrate Terraform with Infracost if you are looking to estimate the cost of every IaC change you make to your cloud infrastructure.
Pulumi vs Terraform: The Similarities
We have observed some major differences when comparing Pulumi vs Terraform. However, since they are both Infrastructures as Code (IaC) tools, Pulumi and Terraform do have some similarities. They include:
- Pulumi and Terraform are both open-source IaC tools.
- They are free to use for individual or self-managed projects. However, both offer advanced enterprise tiers with reasonable pricing models.
- The two platforms support multiple cloud platforms and services. Terraform supports 300+ public clouds and services, and Pulumi supports 60+ cloud providers.
- Pulumi can adapt to all available Terraform providers.
- Pulumi and Terraform provide similar support for existing CI/CD providers like CircleCI, Azure DevOps, GitHub Actions, Jenkins, etc.
- Pulumi and Terraform workflows integrate version control systems like GitHub to maintain infrastructure code files easily.
Pulumi vs Terraform: 10 Key Differences
Pulumi and Terraform seek to accomplish similar cloud engineering goals. Both are effective Infrastructure as Code (IaC) tools with optimized workflows. This aspect explains why Pulumi is considered a Terraform alternative. However, there are some key differences in how they accomplish these goals, which we will explore below:
The biggest difference between the two IaC tools is the use of programming language to write configuration files. Terraform uses a domain-specific language called HashiCorp Configuration Language, which has its own syntax.
Due to general-purpose programming, Pulumi offers robust unit, property, and integration testing and integrates well with native testing frameworks. Developers can write tests in the programming language of their choice.
In contrast, Terraform supports unit tests, contract tests, integration testing, and end-to-end tests with HCL.
Terraform offers various plugins which can be integrated with an IDE. However, Pulumi offers more robust IDE support with commonly used IDEs, including Visual Studio, Xcode, JetBrains, and more, because it supports standard programming languages.
Essentially, with Pulumi, you can do everything within the IDE. For example, you get autocompletion when defining cloud resources, unlike Terraform, which requires the team to consult the relevant cloud provider documentation.
Pulumi and Terraform offer different approaches to state management for provisioning cloud resources. The state keeps track of the metadata about the cloud infrastructure.
By default, Terraform state is self-managed. Primarily, Terraform manually manages concurrency and stores state in a local file named “terraform.tfstate,” which can be hosted on Azure Blob storage, AWS S3, and more. The infrastructure team can also choose to use Terraform Cloud, a SaaS offering where you don’t need to worry about manually hosting “tfstate” files.
On the other hand, Pulumi uses an online or self-hosted backend Pulumi Service application by default, where the desired state is expressed using general-purpose programming languages. However, you can choose to use self-managed object stores like Google Cloud Storage, AWS S3, Azure Blob Storage, etc., to manually manage state using simple JSON files.
Cloud Provider Support
Although Terraform offers support for 300+ cloud providers and services, Pulumi offers dynamic provider support to build custom resources. With Pulumi AWS Native provider, you can provision all existing and newly-released AWS cloud resources easily. Additionally, with Terraform integrations, Pulumi can also cover all Terraform cloud providers.
In the context of Pulumi and Terraform, alias refers to resource renaming and reparenting without replacing it. However, Pulumi goes one step ahead and offers to change the underlying resource type or move the resource to a different stack or workspace entirely. For instance, an alias can be used to change the database resource name.
When it comes to Terraform, an alias provides multi-provider configurations to target multiple cloud regions (like selecting the east and west regions for the same AWS provider) or service hosts.
Modular Infrastructure Support
Due to HCL, Terraform infrastructure components are proprietary and reusable in a similar infrastructure environment. In contrast, Pulumi offers reusable and modular infrastructure components in multiple languages. With Pulumi’s Packages, a module or component developed in one language can be accessible in another language as well.
Policy as Code
Pulumi offers Policy as Code framework via CrossGuard, while Terraform offers it through Sentinel.
Both of these IaC tools have different approaches to secret management (database passwords, user credentials, and tokens). On its part, Terraform uses a separate product named Vault to store secrets, while Pulumi encrypts secrets within state files.
Transformations are callback functions invoked by Pulumi runtime that modify or override input properties of resources, such as adding tags or adding an option to ignore or protect resources. In Terraform, the closest feature similar to Pulumi Transformations is Modules, which have three components:
- input variables
- output values
While input variables can customize Terraform module options, they are not as effective as Pulumi Transformations.
Pulumi and Terraform are robust IaC provisioning tools with various strengths and a handful of weaknesses. Both tools can be used depending on the business requirements and the structure of a company’s DevOps team. Hence, there is no overall competitive edge in the Pulumi vs Terraform debate.
Conventionally, Terraform has been the standard IaC tool in the market, but Pulumi is quickly gaining traction in the last few years as a Terraform alternative. Nonetheless, DevOps teams across organizations typically have their preferences based on the similarities and differences associated with these IaC tools we highlighted. For instance, Terraform requires learning HCL to write configuration files, requiring extra time and effort. As such, startups may choose Pulumi since it has no entry barrier and works with major programming languages like Python, Node.js, and .NET.
On the other hand, some organizations may prefer Terraform due to its extensive documentation, support, and large community in comparison to Pulumi. Additionally, teams may compare enterprise pricing models for both and choose a platform based on their budget limitations.
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