Using Jenkins on DC/OS backed by NFS


​​
In the following blog, I am going to explain about how to use Jenkins on DC/OS and configure NFS for persistence storage. Jenkins on DC/OS works by running the Jenkins master as a one-instance Marathon application. Once the Jenkins master comes online, it registers itself as a Mesos framework (using the jenkins-mesos plugin).

Prerequisites

I assume, you have running cluster of DC/OS on your machine. If not then follow my blog Install DC/OS on Vagrant to install and configure open source DC/OS on vagrant.

About NFS (Network File System) Mounts

NFS, or Network File System, is a distributed filesystem protocol that allows you to mount remote directories on your server. This allows you to leverage storage space in a different location and to write to the same space from multiple servers easily. NFS works well for directories that will have to be accessed regularly.

In my DC/OS cluster, I am running one master and two agent. You can check with vagrant status command:

$ vagrant status


Current machine states:

m1                        running (virtualbox) ===> 192.168.65.90
a1                         running (virtualbox) ===> 192.168.65.111 
a2                         running (virtualbox) ===> 192.168.65.121
p1                         running (virtualbox) ===> 192.168.65.60
boot                      running (virtualbox) ===>

We are going to configure NFS server on p1 VM that will works as NFS server for our a1 and a2 client.

p1 ==> NFS Server ==> 192.168.65.60
a1 ==> Client ==> 192.168.65.111
a2 ==> Client ==> 192.168.65.121

Setup

The system should be set up as root. You can access the root user by typing

$ sudo su

1. Setting Up the NFS Server(192.168.65.60)

a) Download the Required Software

Start off by using yum to install the nfs programs.

$ yum install nfs-utils nfs-utils-lib 

Subsequently, run several startup scripts for the NFS server:

$ chkconfig nfs on 
$ service rpcbind start
$ service nfs start

b)Export the Shared Directory

The next step is to decide which directory we want to share with the
client server. The chosen directory should then be added to the
/etc/exports file, which specifies both the directory to be shared and
the details of how it is shared. We are going to share the directory /jenkins_data.

We need to export the directory:

$ vi /etc/exports 

Add the following lines to the bottom of the file, sharing the directory with the client:


/jenkins_data           192.168.65.111(rw,sync,no_root_squash,no_subtree_check)
/jenkins_data           192.168.65.121(rw,sync,no_root_squash,no_subtree_check)

Once you have entered in the settings for each directory, run the following command to export them:

 $ exportfs -a 

2. Setting Up the NFS Client to Agent a1 (192.168.65.111) and a2 (192.168.65.121)

a) Download the Required Software

Start off by using yum to install the nfs programs.

$ yum install nfs-utils nfs-utils-lib 

b) Mount the Directories
Once the programs have been downloaded to the the client server, create the directory that will contain the NFS shared files

$ mkdir -p /mnt/jenkins 

Then go ahead and mount it

$ mount 192.168.65.60:/jenkins_data /mnt/jenkins 

You can use the df -h command to check that the directory has been mounted. You will see it last on the list.

$ df -h

Filesystem                   Size  Used Avail Use% Mounted on
/dev/mapper/centos-root      8.8G  3.1G  5.7G  35% /
devtmpfs                     739M     0  739M   0% /dev
tmpfs                        749M     0  749M   0% /dev/shm
tmpfs                        749M  8.3M  741M   2% /run
tmpfs                        749M     0  749M   0% /sys/fs/cgroup
/dev/sda1                    497M  164M  334M  33% /boot
none                         455G  164G  292G  36% /vagrant
tmpfs                        150M     0  150M   0% /run/user/501
192.168.65.60:/jenkins_data  8.8G  2.9G  6.0G  33% /mnt/jenkins

Additionally, use the mount command to see the entire list of mounted file systems.

$ mount

systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=28,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
mqueue on /dev/mqueue type mqueue (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
/dev/sda1 on /boot type xfs (rw,relatime,attr2,inode64,noquota)
none on /vagrant type vboxsf (rw,nodev,relatime)
tmpfs on /run/user/501 type tmpfs (rw,nosuid,nodev,relatime,size=153292k,mode=700,uid=501,gid=501)
192.168.65.60:/jenkins_data on /mnt/jenkins type nfs4 (rw,relatime,vers=4.0,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.65.121,local_lock=none,addr=192.168.65.60)

You can ensure that the mount is always active by adding the directory
to the fstab file on the client. This will ensure that the mount starts
up after the server reboots.

$ vi /etc/fstab 

And add blow line:

192.168.65.60:/jenkins_data  /mnt/jenkins   nfs      auto,noatime,nolock,bg,nfsvers=3,intr,tcp,actimeo=1800 0 0

3. Testing the NFS Mount
Once you have successfully mounted your NFS directory, you can test that it works by creating a file on the Client and checking its availability on the Server.

Create a file in the directory to try it out:

$ touch /mnt/jenkins/example 

You should then be able to find the files on the Server in the /jenkins_data.

$ ls /jenkins_data 

4. Installing Jenkins backed by NFS
If you already have a mount point, great! Create an options.json file that resembles the following example:

$ cat options.json
{
    "jenkins": {
        "framework-name": "jenkins-prod",
        "host-volume": "/mnt/jenkins",
        "cpus": 2.0,
        "mem": 4096
    }
}

Then, install Jenkins by running the following command:

$ dcos package install jenkins --options=options.json 

Jenkins will now be available with persistence storage.

Install DC/OS on Vagrant


This installation method uses Vagrant to create a cluster of virtual machines on your local machine that can be used for demos, development, and testing with DC/OS.

Prerequisites

Your machine should have at least 16GB of RAM.

Note: If you are installing DC/OS on Vagrant, it only used for demos, development, and testing. Not use for production.

A) Download DC/OS Installer

First, it’s necessary to download the DC/OS 1.7.0 Installer. Save this somewhere safe – you’ll need this when setting up DC/OS Vagrant:

$ curl -O https://downloads.dcos.io/dcos/EarlyAccess/dcos_generate_config.sh

B) Install DC/OS Vagrant

1. Install & Configure Vagrant & VirtualBox

I assume, you have working Vagrant and VirtualBox on your machine. If not then first of all, Install Vagrant and Virtual box on your system.

Installing Virtualbox:

 $ sudo apt-get install virtualbox

Installing Vagrant:

$ sudo apt-get install vagrant

Install the dkms package to ensure that the VirtualBox host kernel modules (vboxdrv, vboxnetflt and vboxnetadp) are properly updated if the Linux kernel version changes during the next apt-get upgrade.

$ sudo apt-get install virtualbox-dkms

2. Clone DC/OS Vagrant Repo

Change the directory where you want to run the DC/OS and clone the dcos-vagrant repo and cd into it.

$ git clone https://github.com/dcos/dcos-vagrant
$ cd dcos-vagrant

You can also upgrade the latest version of dcos-vagrant:

  • Change into the repo directory (e.g. cd ~/workspace/dcos-vagrant)
  • Checkout the new desired version (e.g. git checkout v0.6.0)
  • Pull the new code (e.g. git pull)

3. Configure VirtualBox Networking

Configure the host-only vboxnet0 network to use the 192.168.65.0/24 subnet.

Create the vboxnet0 network if it does not exist:

$ VBoxManage list hostonlyifs | grep vboxnet0 -q || VBoxManage hostonlyif create

Set the vboxnet0 subnet:

$ VBoxManage hostonlyif ipconfig vboxnet0 --ip 192.168.65.1

4. Install Vagrant Host Manager Plugin

The Host Manager Plugin manages the /etc/hosts on the VMs and host to allow access by hostname.

$ vagrant plugin install vagrant-hostmanager

This will update /etc/hosts every time VMs are created or destroyed.

5. Download the DC/OS Installer

As we already downloaded, we need to move dcos_generate_config.sh to the root of the repo (the repo will be mounted into the vagrant machines as /vagrant).

$ cd dcos_generate_config.sh dcos-vagrant

6. Configure the DC/OS Installer

As we have downloaded DC/OS 1.7.0 Installer so we will export etc/config-1.7.yaml to DCOS_CONFIG_PATH env variable.

$ export DCOS_CONFIG_PATH=etc/config-1.7.yaml

The path to the config file is relative to the repo dir, because the repo dir will be mounted as /vagrant within each VM. Alternate configurations may be added to the <repo>/etc/ dir and configured in a similar manner.

7. Configure the DC/OS Machine Types

There is sample VagrantConfig.yaml.example dcos-vagrant repo that we can configure for DC/OS machine type. At this point of time, we not need to do any changes.

cd <repo>
cp VagrantConfig.yaml.example VagrantConfig.yaml
8. Download the VM Base Image

By default, Vagrant will automatically download the latest VM Base Image (virtualbox box) when you run vagrant up <machines>, but since downloading the image takes a while the first time, you may want to trigger the download manually.

$ vagrant box add https://downloads.dcos.io/dcos-vagrant/metadata.json

If you already have the latest version downloaded, the above command will fail.

9. Deploy DC/OS

Specify which machines to deploy in your cluster. Below are a few options to try.

a) Minimal Cluster

A minimal cluster supports launching small Marathon apps. Most other services will fail to install, because they require more than one agent node.

Requires > 4.5GB free memory (using the example VagrantConfig).

$ vagrant up m1 a1 boot

b) Small Cluster

A small cluster supports running tasks on multiple nodes.

Requires > 7.25GB free memory (using the example VagrantConfig).

$ vagrant up m1 a1 a2 p1 boot

c) Medium Cluster

A medium cluster supports the installation of a minimally configured Cassandra.

Requires > 10GB free memory (using the example VagrantConfig).

$ vagrant up m1 a1 a2 a3 a4 p1 boot

d) Large Cluster

Requires > 17GB free memory (using the example VagrantConfig).

A large cluster supports master node fail over, multiple framework installs, and multiple public load balancers.

$ vagrant up m1 m2 m3 a1 a2 a3 a4 a5 a6 p1 p2 p3 boot
10. Access DC/OS from browser

Once the the machines are created and provisioned, DC/OS will be installed. Once complete, the Web Interface will be available at http://m1.dcos/.

11. Additionally you can Authentication DC/OS

If your DC/OS CLI or the web dashboard prompt for username and password then the superuser credentials are by default admin/admin