Jenkins Remoting

Jenkins Remoting is a library, and executable Java archive, which implements the communication layer in Jenkins. This includes the TCP-based communication protocols, remote procedure calls, class loading, data streaming, etc. Currently Remoting is primarily used in communications between the Jenkins controller and Jenkins agents.

The Remoting sub-project includes the Remoting library itself, package for agents, and a number of Remoting-specific plugins and core modules.

Remoting Usage in Jenkins

Agent executables (remoting.jar is a named agent.jar or slave.jar in Jenkins)
Controller to Agent communication protocols being used in various Agent types, including Java Web Start (aka JNLP) and plugin:ssh-slaves[SSH] agents
Jenkins CLI, Remoting mode is deprecated since 2.54 (announcement)
Communication with Maven instance in the plugin:maven-plugin[Maven Integration plugin].

Project Components

Remoting Library

Remoting Library is the main component of the the sub-project. The code base is located in a separate repository, which also contains Remoting developer and user documentation. This library also has an independent release cycle and LTS release lines.

Links:

Jenkins Core and Modules

Although Remoting library is a standalone component, Jenkins core includes some extensions and modules for working with Remoting. Core extensions also allow implementing custom protocols on-demand (e.g. for Jenkins CLI). There is ongoing activity on detaching these core components to Jenkins plugins (see https://issues.jenkins.io/browse/JENKINS-44099), but in the meantime upgrading of Jenkins core may be required to fix Remoting issues.

Jenkins core extensions:

Agent Protocol - Protocol Implementations
JNLP Agent Receiver - Receives Incoming connections

Modules:

Agent Installer Module - Generic API for Remoting Agent installations
Windows Agent Installer Module - Provides logic for installing Jenkins agents as Windows services, powered by WinSW project
etc.

Packaging

There are several packages which bundle the Remoting library and allow connecting Jenkins agents via one of remoting protocols.

Docker Agent: Base image, which bundles Remoting
Docker Inbound Agent: Image, which can be used to connect agents using TCP (JNLP protocols) or WebSockets
Jenkins CLI executable (Requires Remoting CLI to be enabled on the Jenkins controller)
Swarm Agent Connector executable in Swarm Plugin