docker service create --name jenkins-master \
	-p 50000:50000 \
	-p 80:8080 jenkins

• port 50000 used by all joining slaves created in the next step.
• created as a service so that docker swarm will manage the container and reschedule it if needed.
• /var/jenkins_home is used for all data so in a real deployment this need to be either a mount a folder from the host or use some docker storage driver.

• Pipeline the new Pipeline as Code plugin that allows to specify the steps in a Jenkinsfile
• GitHub plugin to checkout and push to github
• Self-Organizing Swarm Plug-in Modules deploy each Docker swarm node as a jenkins slave
• GitHub Branch Source Plugin scan a github account and automatically create jobs for repos that have a Jenkinsfile in the root directory. It also creates a github webhook so every repo push will trigger a build.

first create a secret that will be used by the Jenkins slaves to connect to the master

echo "-master http://10.0.0.101 -password admin -username admin"|docker secret create jenkins-v1 -

• 10.0.0.101 replace it with actual Jenkins master IP
• jenkins-v1 instead of just jenkins so that we can rotate the passwords - Docker docs

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/" \
	--secret source=jenkins-v1,target=jenkins \
	vipconsult/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/" \
	--secret source=jenkins-v1,target=jenkins \
	vipconsult/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/" \
	--secret source=jenkins-v1,target=jenkins \
	vipconsult/jenkins-swarm-agent

• vipconsult/jenkins-swarm-agent is simple image that runs the jenkins swarm plugin which connects to a given master using parameters from the Docker secret
• 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")
• secret source=jenkins-v1,target=jenkins using the secret created in the previous step, needs to match a user on the jenkins master

Create a new GitHub Organization job using the Jenkins GUI - this will scan all repositories for a Jenkinsfile in the root directory and add it as a new job.

• Owner this is the github account or organization - vipconsult in this case
• Scan credentials need to add some github credentials - anonymous github api requests are limited and will fail to scan all repositories.
• The Jenkinsfile is set to use credentials with ID "DockerHub" so also need to create those.

Using the Github Webhooks every repo change will trigger a new build.

In my case the jenkins master is behind a router so the webhook was created with my internal IP so I needed to open a firewall port so that the webhook can hit the Jenkins master. Here is a little nifty tool that simplifies the whole process and works even when you don't have access to the router. It uses UPNP protocol to automatically open and map a port to your Jenkins master machine

apt-get install miniupnpc
upnpc -a 10.0.0.101 80 8081 tcp

• 10.0.0.101 Jenkins master internal IP
• 80 Jenkins Master port
• 8081 external port useg by Github webhooks so after this Github can send webhooks using your external ip and the external port like http://216.58.213.78:8081/

Just fork the project and change the docker hub username at the top of the Jenkinsfile.