Concepts

What is DevOps?

Azure DevOps is a SaaS Agile/Build and Release tool for Software Developers and DevOps Engineers enabling automation of the build and deployment of code
Azure DevOps (Azure DevOps Services and Azure DevOps Server) are the new releases of Visual Studio Team Services (VSTS) and Team Foundation Server (TFS) respectively
Azure DevOps comprises a range of services covering the full development life-cycle and enables DevOps capabilities

DevOps Server: Azure DevOps Server is a Microsoft product that covers the entire application lifecycle, and enables DevOps capabilities, on-premises offering
DevOps Service: Cloud hosted verson of Azure DevOps Server managed by Microsoft

Boards: Kanban board, Scrum tool
Repos: Cloud-hosted private Git repository
Pipelines: CI/CD pipelines
Artifacts: Create, host, and share packages
Test Plans: Test and ship with confidence using manual and exploratory testing tools

A DevOps pipeline is a set of automated processes and tools that allows developers (Dev) and operations professionals (Ops) to collaborate on:
- Merge, build and test code
- Produce artifacts
- Deploy artifacts to target environments
A pipeline is one or more stages that describe a CI/CD process
A pipeline can deploy to one or more environments
Pipelines automatically builds and tests code projects to make them available to others
Types of pipeline: There 2 types of pipelines
- YAML pipeline
- Classic Pipeline : UI based (might be deprecated in favor of YAML)
See: YAML pipeline

An artifact is a collection of files or packages published by a run
Artifacts are made available to subsequent tasks i.e deployment (release pipeline)
Details: Azure DevOps artifacts

An agent is computing infrastructure with installed agent software that runs one job at a time
Instead of managing each agent individually, agents are organizied into agent pools
In Azure Pipelines, pools are scoped to the entire organization (so that agent machines can be shared across projects)
An agent is registered with a single pool
When a pipeline is created, which pool the pipeline will use must be specified

Pipeline Agent

Underlaying VM that executes the pipeline job (workload)
Types of Agent:
- Microsoft Hosted
  - Microsoft-hosted agents that run Windows and Linux images are provisioned on Azure general purpose virtual machines
  - Maintenance and upgrades are taken care of for you
  - Each time you run a pipeline, you get a fresh virtual machine. The virtual machine is discarded after one use
  - Microsoft-hosted agents can run jobs directly on the VM or in a container
  - Azure Pipelines provides a pre-defined agent pool named Azure Pipelines with Microsoft-hosted agents
  - See: https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/hosted?view=azure-devops
- Self Hosted: An agent that you set up and manage on your own to run jobs
Links:
- https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/agents
- https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/scale-set-agents?view=azure-devops