cqlcorp/jenkins-swarm-agent is simple image that runs the jenkins swarm plugin jar file which connects to a given master using parameters

https://wiki.jenkins-ci.org/display/JENKINS/Swarm+Plugin

On the testing docker swarm

docker service create \
	--mode=global \
	--name jenkins-swarm-agent \
	-e LABELS=docker-test \
	--mount "type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock" \
	--mount "type=bind,source=/tmp/,target=/tmp/" \
	cqlcorp/jenkins-swarm-agent

On the staging docker swarm

docker service create \
	--mode=global \
	--name jenkins-swarm-agent \
	-e LABELS=docker-stage \
	--mount "type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock" \
	--mount "type=bind,source=/tmp/,target=/tmp/" \
	cqlcorp/jenkins-swarm-agent

On the production Docker swarm

docker service create \
	--mode=global \
	--name jenkins-swarm-agent \
	-e LABELS=docker-prod \
	--mount "type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock" \
	--mount "type=bind,source=/tmp/,target=/tmp/" \
	cqlcorp/jenkins-swarm-agent

mode=global when we add new nodes to the Docker cluster they will all connect to the jenkins master to serve as slaves
mount "type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock" we mount the Docker socket so that we can use the Docker client inside a container to start new containers or services directly on the host. This is a better approach than Docker in Docker
mount "type=bind,source=/tmp/,target=/tmp/" all containers can share files generated by the same Jenkins job
LABELS=docker-test the jenkins slave label. This is used when you define where to run each pipeline step - the labels need to match the ones used in the Jenkinsfile - node("docker-test") , node("docker-stage") , node("docker-prod")

Required env variables:

-e JENKINS_URL=https://jenkins.example.com
-e JENKINS_SSL_FINGERPRINTS=SHA256FINGERPRINTS
-e JENKINS_USERNAME=AgentUsername

The password for the Jenkins username should be set as a secret named jenkins-agent-password.

Supported env variables - if not set the defaults are used

-e LABELS="docker" - node labels
-e EXECUTORS="3" - number of executors
-e FSROOT="/tmp/jenkins" - data directory , jenkins need to have write access to - best to leave the defaults.

Credits

Initially cloned from vipconsult/jenkins-swarm-agent and updated to suit our needs.