On-Premises or Hosted Build Agents?

Whether you choose an on-premises or hosted service, there are many times when development teams need full control over build agents. The build process consists of two things: the build controller and the build agent. A build controller is the orchestrator that manages the pool of existing agents, and the build agent handles the actual build process. Build agents are typically hosted on separate machines or in Docker containers, enabling them to scale out based on demand.

A build agent is responsible for getting the source files, instrumenting the workspace, compiling the code, running all required tests, and then producing the final version of the product. Most of the continuous delivery (CD) solutions available on the market today offer a variation of configurable build agents. For example, Visual Studio Team Services (VSTS) enables an organization to manually create agent pools and subsequently provision those with an unlimited number of build agents that can sport a number of declared capabilities. Whenever a build kicks off in VSTS, agent pools are inspected based on the given demands to pick the right agent. TeamCity, another CD service, offers the capability to create custom build agents that are installed and configured separately from the TeamCity server. Atlassian (https://www.atlassian.com) supports both local and remote Bamboo agents, in addition to being able to handle elastic agents—a flavor of remote agents that run in Amazon Elastic Compute Cloud.