The Swarm plugin enables nodes to join a nearby Jenkins controller, thereby forming an ad-hoc cluster. This plugin makes it easier to scale a Jenkins cluster by spinning up and tearing down new agents, enabling team members to contribute compute resources to a build farm or to attach agents to which the Jenkins controller cannot initiate connections.

This plugin consists of two pieces:

  1. A self-contained client that can join an existing Jenkins controller.

  2. A plugin that needs to be installed on the Jenkins controller to accept Swarm clients.

With the Swarm client, a person who is willing to contribute some of his computing power to the cluster just needs to run a virtual machine with the Swarm client and the cluster gets an additional agent. Because the Swarm client is running on a separate VM, there is no need to worry about the builds/tests interfering with the host system or altering its settings unexpectedly.

Getting started

  1. Install the Swarm plugin from the Update Center.

  2. Ensure your agent is running version 11 or later of the Java Runtime Environment (JRE). The recommendation is to use the same JRE distribution and version as the controller.

  3. Download the Swarm client from ${JENKINS_URL}/swarm/swarm-client.jar on your agent.

  4. Run the Swarm client with java -jar path/to/swarm-client.jar -url ${JENKINS_URL} -username ${USERNAME} and one of the authentication options as described in the Global Security Configuration documentation. There are no other required command-line options; run with the -help option to see the available options.

Available options

$ java -jar swarm-client.jar -help

Name Description

-config FILE

YAML configuration file containing the options.


Delete any existing agent with the same name. (default: false)

-description VAL

Description to be put on the agent.


Disable client’s unique ID. (default: false)


Disable SSL verification in the HTTP client. (default: false)


Disable Remoting working directory support and run the agent in legacy mode. (default: false)

-e (--env)

An environment variable to be defined on this agent. It is specified as `key=value'. Multiple variables are allowed.

-executors N

Number of executors (default: number of CPUs)


Fail if the requested Remoting working directory or internal directory is missing. (default: false)

-fsroot FILE

Remote root directory. (default: .)

-help (--help, -h)

Show the help screen (default: false)

-internalDir FILE

The name of the directory within the Remoting working directory where files internal to Remoting will be stored.

-jar-cache FILE

Cache directory that stores JAR files sent from the controller.


Do not remove clients from the controller when the agent becomes disconnected. (default: false)

-labels VAL

Whitespace-separated list of labels to be assigned for this agent. Multiple options are allowed.

-labelsFile VAL

File location with space delimited list of labels. If the file changes, the client is restarted.

-maxRetryInterval N

Max time to wait before retry in seconds. Default is 60 seconds. (default: 60)

-mode MODE

The mode controlling how Jenkins allocates jobs to agents. Can be either `normal' (use this node as much as possible) or `exclusive' (only build jobs with label expressions matching this node). Default is `normal'. (default: normal)

-name VAL

Name of the agent.


Do not retry if a successful connection gets closed. (default: false)

-password VAL

The Jenkins user API token or password.

-passwordEnvVariable VAL

Environment variable containing the Jenkins user API token or password.

-passwordFile VAL

File containing the Jenkins user API token or password.

-pidFile VAL

File to write PID to. The client will refuse to start if this file exists and the previous process is still running.

-prometheusPort N

If defined, then start an HTTP service on this port for Prometheus metrics. (default: -1)

-retry N

Number of retries before giving up. Unlimited if not specified. (default: -1)


The mode controlling retry wait time. Can be either `none' (use same interval between retries) or `linear' (increase wait time before each retry up to maxRetryInterval) or `exponential' (double wait interval on each retry up to maxRetryInterval). Default is `none'. (default: NONE)

-retryInterval N

Time to wait before retry in seconds. Default is 10 seconds. (default: 10)

-sslFingerprints VAL

Whitespace-separated list of accepted certificate fingerprints (SHA-256/Hex), otherwise system truststore will be used. No revocation, expiration or not yet valid check will be performed for custom fingerprints! Multiple options are allowed. (default: )

-t (--toolLocation)

A tool location to be defined on this agent. It is specified as `toolName=location'.

-tunnel VAL

Connect to the specified host and port, instead of connecting directly to Jenkins. Useful when connection to Jenkins needs to be tunneled. Can be also HOST: or :PORT, in which case the missing portion will be auto-configured like the default behavior

-url (-master) VAL

The complete target Jenkins URL like `http://server:8080/jenkins/'.

-username VAL

The Jenkins username for authentication.


Connect using the WebSocket protocol. (default: false)

-webSocketHeader NAME=VALUE

Additional WebSocket header to set, e.g. for authenticating with reverse proxies. To specify multiple headers, call this flag multiple times, one with each header.

-workDir FILE

The Remoting working directory where the JAR cache and logs will be stored.


Report issues and enhancements in the Jenkins issue tracker. Use the swarm-plugin component in the JENKINS project.


Refer to our contribution guidelines.