Installing Docker Swarm
I have chosen to use CentOS 7 for my cluster of machines. So these instructions are for CentOS 7.
First I need to install docker on all of the machines in the cluster.
Set up yum so it can see the latest docker packages.
# sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
Next install docker onto each machine in your cluster.
# sudo yum install docker-ce
Once you have installed docker on every node in your cluster you can now set up your swarm. First you have to choose which machines will be your manager(s).
On one of the masters you need to initialize the swarm
# docker swarm init
If your machine has more than one network then you will need to specify the ip address to use for the master.
# docker swarm init --advertise-addr 172.16.0.100
Swarm initialized: current node (a2anz4z0mpb0vmcly5ksotfo1) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join \ --token SWMT....wns 172.16.0.100:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
In this example the IP address is 172.16.0.100 for the swarm master. Now on each worker node I just run the join command as specified in the output of the init command.
# docker swarm join --token SWMT...wns 172.16.0.100:2377
If you want to add another master then you run the command
# docker swarm join-token manager
It will tell you exactly what you need to do.
Setting up Jenkins in your Swarm
Now this is the easy part. Sort of. With docker swarm and services this has just gotten much easier. There are several docker images that are available with jenkins already installed in them. So it is best if we just use one of them. The most popular is "jenkins". Go figure. Now with the image name all we need to do is start a service in the swarm. We can simply write a small compose file and we will be set.
# docker-jenkins.yaml
version: '3'
services:
jenkins:
image: jenkins
ports:
- "8082:8080"
- "50000:50000"
environment:
JENKINS_OPTS: --prefix=/jenkins
deploy:
placement:
constraints: [node.role == manager]
volumes:
- $PWD/docker/jenkins:/var/jenkins_home
There are a couple of things to note.
- Ports - First the ports are mapped to 50000 and 8082. This are external ports and will be accessible outside of the container.
- Environment - You can set any jenkins options on this line any following environment lines
- Volumes - This will give us the ability to "mount" a directory from the host machine into the container. So if the container goes down we still have our jenkins installation. You will need to create the directory using
# mkdir ~/docker/jenkins && chmod 777 ~/docker/jenkins
if you don't do this you will have problems with jenkins coming up.
Now it is time to actually start the service.
Two things where created when the deploy was run. A default network "build_default" and the service "build_jenkins" notice all of the artifacts created will begin with "build_". The default network is created when a network is not specified.
# docker stack deploy -c docker-jenkins.yaml buildCreating network build_default
Creating service build_jenkins
Two things where created when the deploy was run. A default network "build_default" and the service "build_jenkins" notice all of the artifacts created will begin with "build_". The default network is created when a network is not specified.
Now you should be able to access the jenkins web site at
http://172.16.0.100:8082/jenkins
Jenkins now requires a password when you install. You can find the password in the secrets directory in the docker/jenkins base directory.
# cat ~/docker/jenkins/secrets/initialAdminPassord
asldfkasdlfkjlasdfj23iwrh
Cut and paste this into your browser and you will be set and ready to go.
Debugging Tools
Here are a couple of things I found useful when I was setting up the environment.
# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
91aa53f4642a jenkins@sha256:c0cac51cbd3af8947e105ec15aa4bcdbf0bd267984d8e7be5663b5551bbc5f4b "/bin/tini -- /usr..." 5 hours ago Up 5 hours 8080/tcp, 50000/tcp build_jenkins.1.abu55c8tybjwrsd35ouaor1d2
Shows the containers that are currently running. This will include the containers that are running the services. I found that some of the containers never started up. So I was trying to find out what happen. So I ran the following command:
# docker service ps build_jenkins
ID NAME IMAGE NODE DESIRED ST ATE CURRENT STATE ERROR PORTSThis will show the tasks for the services before the containers get launched and their status.
abu55c8tybjw build_jenkins.1 jenkins:latest node0.intel.local Running Running 5 hours ago
nac73zp1gc68 \_ build_jenkins.1 jenkins:latest node0.intel.local Shutdown Failed 5 hours ago "task: non-zero exit (1)"
xyrmzvx1pnnp \_ build_jenkins.1 jenkins:latest node0.intel.local Shutdown Failed 5 hours ago "task: non-zero exit (1)"
phycp5ypp61o \_ build_jenkins.1 jenkins:latest node0.intel.local Shutdown Failed 5 hours ago "task: non-zero exit (1)"
o3ewixv3hvcy \_ build_jenkins.1 jenkins:latest node0.intel.local Shutdown Failed 5 hours ago "task: non-zero exit (1)"
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