Jenkins Distributed Builds Flashcards

What is a Jenkins agent (formerly called a slave)?

Answer: A machine that runs build jobs delegated by the Jenkins controller

A Jenkins agent is a separate machine (physical, VM, or container) that the Jenkins controller connects to and delegates build execution.

What are the two primary methods for connecting a Jenkins agent to the controller?

Answer: JNLP (inbound/WebSocket) and SSH

Jenkins agents connect either via SSH (controller initiates connection) or JNLP/WebSocket (agent initiates inbound connection to the controller).

What is a Jenkins 'label' used for in the context of distributed builds?

Answer: Tags agents with capabilities so pipeline stages can target the right agent type

Labels are tags assigned to agents (e.g., 'linux', 'docker', 'windows') that allow pipeline stages to request a specific type of agent using `agent { label 'linux' }`.

What happens to a Jenkins build when no agent matching the requested label is available?

Answer: The build stays in the queue until a matching agent becomes available

Jenkins queues builds that cannot find a matching agent and starts them as soon as an agent with the required label becomes available.

What is the difference between an online and offline Jenkins agent?

Answer: Online agents are connected and available for builds; offline agents are disconnected and cannot accept builds

An online agent has an active connection to the Jenkins controller and can be assigned builds, while an offline agent is disconnected and will cause builds to wait in the queue.

What is the purpose of setting a 'Remote Root Directory' when configuring a Jenkins agent?

Answer: Defines the file system path on the agent where Jenkins stores workspaces and temp files

The Remote Root Directory is the base path on the agent machine where Jenkins creates workspaces, archives, and temporary files during builds.