Concept
Azure DevOps Server (formerly Team Foundation Server (TFS) and Visual Studio Team System (VSTS)) is a Microsoft product that provides version control (either with Team Foundation Version Control (TFVC) or Git), reporting, requirements management, project management (for both agile software development and waterfall teams), automated builds, testing and release management capabilities. It covers the entire application lifecycle and enables DevOps capabilities. Azure DevOps can be used as a back-end to numerous integrated development environments (IDEs) but is tailored for Microsoft Visual Studio and Eclipse on all platforms. Azure DevOps is available in two different forms: on-premises ("Server") and online ("Services"). The latter form is called Azure DevOps Services (formerly Visual Studio Online before it was renamed to Visual Studio Team Services in 2015). The cloud service is backed by the Microsoft Azure cloud platform. It uses the same code as the on-premises version of Azure DevOps, with minor modifications, and implements the most recent features. A user signs in using a Microsoft account to set up an environment, creating projects and adding team members. New features developed in short development cycles are added to the cloud version first. These features migrate to the on-premises version as updates, at approximately three-month intervals. Azure DevOps is built on multi-tier, scalable architecture. The primary structure consists of an application tier responsible for processing logic and maintaining the web application portal (referred to as Team Web Access or TWA). Azure DevOps is built using Windows Communication Foundation web services. These may be consumed by any client, although the client object model is recommended. The data tier and application tier can exist on the same machine. To support scalability, the application tier can be load balanced and the data tier can be clustered. If using Microsoft SQL Server 2012 or later, AlwaysOn SQL Server Failover Clusters and Availability Groups are supported which allows for geographic replication of data.