Concepts

What is Infrastructure as code?

Infrastructure as code (IaC) means to manage IT infrastructure using code
- Code can be domain specific language (DSL) or real programming language
- DSL i.e. HCL in Terraform
- C# (+ many more labguage) in Pulumi
- ARM Template (Azure)
IaC allows you to automate the provisioning of your cloud resources using code
Defining provisioning application infrastructures using code
IaC helps IT operations teams manage and provision IT infrastructure automatically through code without relying on manual processes
IaC is a concept and there are IaC tools( i.e. Terraform, Pulumi, Cloudformation etc.) that helps to automate different tasks (provisioning and managing infrastructure)
Treating infrastructure the same way we treat code

IaC approaches

A Pulumi project is any folder which contains a Pulumi.yaml file
- Pulumi.yaml project file specifies metadata about your project
- The project file must begin with a capitalized P (Pulumi/yaml, not pulumi.yaml)
Project is a directory that contains source code for the program and metadata on how to run the program
A project specifies which runtime to use and determines where to look for the program that should be executed during deployments
Pulumi program
- Describes the target infrastructure written in specified programming language i.e. C#
- Resides in a project
- Contains all of the cloud resources you define in you Pulumi code
- pulumi up creates an instance of Pulumi Program which is known as “Stack”
https://www.pulumi.com/docs/intro/concepts/project/

A stack is an isolated, independently configurable instance of a Pulumi program
Each stack has its own separate configuration and secrets, role-based access controls (RBAC) and policies, and concurrent deployments.
See: details about Stack in Pulumi

Pulumi stores metadata about infrastructure so that it can manage the corresponding cloud resources and that metadata is called State (Stack State)
For detaisl, see Pulumi Stack State

Pulumi stores Stack State in a backend (A backend is an API and storage endpoint used by the CLI)
For detaisl, see Pulumi Stack State Backend

A CLI (command line interface) tool to interact with Pulumi runtime
- Pulumi is controlled primarily using CLI
- Pulumi CLI is what converts code into running cloud infrastructure
Pulumi CLI works in conjunction with stack state backend (i.e. Pulumi service) to deploy changes to the cloud infrastructure and apps
It keeps a history of who updated what in your team and when
Pulumi CLI has been designed for:
- continuous integration and delivery scenarios
- inner loop productivity
Common CLI commands: https://www.pulumi.com/docs/reference/cli/#common-commands