Since I started playing with Docker I have been thinking that its network implementation is something that will need to be improved before I could really use it in production. It is based on container links and service discovery but it only works for host-local containers. This creates issues for a few use cases, for example when you are setting up services that need advanced network features like broadcasting/multicasting for clustering. In this case you must deploy your application stack containers in the same Docker host, but it makes no sense to deploy a whole cluster in the same physical or virtual host. Also I would like containers networking to function without performing any action like managing port mappings or exposing new ports. This is why networking is one of my favorite features of Rancher, because it overcomes Docker network limitations using a software defined network that connects all docker containers under the same network as if all of them were physically connected. This feature makes it much easier to interconnect your deployed services because you don’t have to configure anything. It just works. **** ****However I was still missing the possibility to easily reach my containers and services from my PC as if I also was on the same network again without configuring new firewall rules or mapping ports. That is why I created a Docker image that extends Rancher network using OpenVPN. This allows any device that may run OpenVPN client including PCs, gateways, and even mobile devices or embedded systems to access your Rancher network in an easy and secure way because all its traffic is encrypted. There are many use cases and possibilities for using this, I list some examples:

Allow all users in your office to access your containers

Enabling oncall sysadmins to access your containers from anywhere at any time

Or the example that we are carrying out: allowing a user who works at home to access your containers

And all this without reconfiguring your Rancher environment every time that you grant access to someone. In this post we are installing a minimalistic Continuous Integration (CI) environment on AWS using Rancher and RancherOS. The main idea is to create a scenario where a developer who teleworks can easily access our CI environment, without adding IPs to a whitelist, exposing services to the Internet nor performing special configurations. To do so we are installing and configuring these docker images:

jenkins: a Jenkins instance to compile a sample WAR hosted in github. Jenkins will automatically deploy this application in tomcat after compiling it.

tutum/tomcat:7.0 - a Tomcat instance for deploying the sample WAR

nixel/rancher-vpn-server: a custom OpenVPN image I have created specially to extend Rancher network

And we are using a total of 4 Amazon EC2 instances:

1 for running Rancher Server

1 for running VPN server

1 for running Tomcat server

1 for running Jenkins

* * At the end the developer will be able to browse to Jenkins and Tomcat webapp using his VPN connection. As you will see, this is easy to achieve because you are not configuring anything for accessing Tomcat or Jenkins from your PC, you just launch a container and you are able to connect to it.

Preparing AWS cloud

You need to perform these actions on AWS before setting up the CI environment. Creating a Key Pair Go to EC2 Console and enter Key Pairs section. When you create the Key Pair your browser will download a private key that you will need later for connecting to your Rancher Server instance using SSH if you want to. Save this file because you won’t be able to download it from AWS anymore. Creating a Security Group Before creating a Security Group go to VPC Console and choose one VPC and Subnet where you will deploy your EC2 instances. Copy the VPC ID and Subnet ID and CIDR. Go to EC2 Console and create a Security Group named Rancher which will allow this inbound traffic:

Allow 22/tcp, 2376/tcp and 8080/tcp ports from any source, needed for Docker machine to provision hosts

Allow 500/udp and 4500/udp ports from any source, needed for Rancher network

Allow 9345/tcp and 9346/tcp ports from any source, needed for UI features like graphs, view logs, and execute shell

Allow 1194/tcp and 2222/tcp ports from any source, needed to publish our VPN server container

Be sure to select the appropriate VPC in the Security Group dialog. Creating an Access Key On EC2 Console click your name in the top menu bar and go to Security Credentials. Expand Access Keys (Access Key ID and Secret Access Key) option and create a new Access Key. Finally click Download Key File because again you won’t be able to do it later. You will need this for Rancher Server to create Docker hosts for you.

Installing Rancher Server

Create a new instance on EC2 console that uses rancheros-0.2.1 AMI, search for it in Community AMIS section. For this tutorial I am using a basic t1.micro instance with 8GB disk, you may change this to better fit your environment needs. Now enter Configure Instance Details screen and select the appropriated Network and Subnet. Then expand Advanced Details section and enter this user data:

#!/bin/bash docker run -d -p 8080 :8080 rancher/server:v0.14.2

This will install and run Rancher Server 0.14.2 when the instance boots. Before launching the new instance be sure to choose the Security Group and Key Pair we just created before. Finally go to Instances menu and get your Rancher Server instance public IP. After some minutes navigate to http://RANCER_SERVER_PUBLIC_IP:8080 and you will enter Rancher UI.

Provisioning Docker hosts

In this section we are creating our Docker hosts. Go to Rancher UI and click Add Host button, confirm your Rancher Server public IP and then click Amazon EC2 provider. In this form you need to enter the following data: host name, Access Key, Secret Key, Region, Zone, VPC ID, Subnet ID, and Security Group. Be sure to enter the appropriated values for Region, Zone, VPC ID and Subnet ID because they must match those used by Rancher Server instance. You must specify Security Group name instead its ID, in our case it is named Rancher. Repeat this step three times so Rancher will provision our three Docker hosts. After some minutes you will see your hosts running in Rancher UI.

Installing VPN container

Now it’s time to deploy our VPN server container that will extend the Rancher network. Go to your first host, click Add Container button and follow these steps:

Enter a name for this container like rancher-vpn-server Enter docker image: nixel/rancher-vpn-server:latest Add this TCP port map: 1194 (on Host) to 1194 (in Container) Add this TCP port map: 2222 (on Host) to 2222 (in Container)

Now expand Advanced Options section and follow these steps:

In Volume section add this new volume to persist VPN configuration: /etc/openvpn:/etc/openvpn In Networking section be sure to select Managed Network on docker0 In Security/Host section be sure to enable the Give the container full access to the host checkbox

After a while you will see your rancher-vpn-server container running on your first host. Now you are about to use another nice Rancher feature. Expand your rancher-vpn-server container menu and click View Logs button as you can see in the following image: Now scroll to top and you will find the information you need in order to connect with your VPN client. We are using this data later. **** ****

Installing Tomcat container

To install Tomcat container you have to click Add Container button on your second host and follow these steps:

Enter a name for this container like tomcat Enter docker image: tutum/tomcat:7.0 *No port map is required* Expand Advanced Options and in Networking section be sure to select Managed Network on docker0

After a while you will see your Tomcat container running on your second host. Now open Tomcat container logs in order to get its admin password, you are needing it later when configuring Jenkins.

Installing Jenkins container

Click Add Container button on your third host and execute the following steps:

Enter a name for this container like jenkins Enter docker image: jenkins No port map is required

Now expand Advanced Options section and follow these steps:

In Volume section add this new volume to persist Jenkins configuration: /var/jenkins_home In Networking section be sure to select Managed Network on docker0

After a while you will see your Jenkins container running on your third host.

Putting it all together

In this final step you are going to install and run the VPN client. There are two ways to get the client working: using a Docker image I have prepared that does not require any configuration, or using any OpenVPN client that you will need to configure. Once the VPN client is working you are browsing to Jenkins in order to create an example CI job that will deploy the sample WAR application on Tomcat. You will finally browse to the sample application so you can see how all this works together. Installing Dockerized VPN client In a PC with Docker installed you will execute the command that we saw before in rancher-vpn-server container logs. According to my example I will execute this command:

sudo docker run -ti -d --privileged --name rancher-vpn-client -e VPN_SERVERS=54.149.62.184:1194 -e VPN_PASSWORD=mmAG840NGfKEXw73PP5m nixel/rancher-vpn-client:latest

Adapt it to your environment. Then show rancher-vpn-client container logs:

sudo docker logs rancher-vpn-client

You will see a message printing the route you need to add in your system in order to be able to reach Rancher network. In my case I’m executing this command:

sudo route add -net 10.42.0.0/16 gw 172.17.0.8

At this point you are able to ping all your containers, no matter in which host they run. Now your PC is actually connected to Rancher network and you can reach any container and service running on your Rancher infrastructure. If you repeat this step in a Linux Gateway at your office you will, in fact, expose Rancher network to all the computers connected in your LAN, which is really interesting. Installing a custom OpenVPN client If you prefer to use an existing or custom OpenVPN client, you can do it. You will need your OpenVPN configuration file that you can get executing the SSH command that we got before in rancher-vpn-server container log. In my case I can get RancherVPNClient.ovpn file executing this command:

sshpass -p mmAG840NGfKEXw73PP5m ssh -p 2222 -o ConnectTimeout=4 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no root@54.149.62.184 "get_vpn_client_conf.sh 54.149.62.184:1194" > RancherVPNClient.ovpn

Now, for example, you can execute OpenVPN executing this command:

/usr/sbin/openvpn --config RancherVPNClient.ovpn

You can also use OpenVPN iOS/Android application with this RancherVPNClient.ovpn file and you will also be able to access your Rancher network from your mobile or tablet. Again, you can extend your VPN for all users in your LAN if you repeat this step in a Linux Gateway in your office. Configuring Jenkins Now it’s time to configure Jenkins to compile and deploy our sample WAR in Tomcat. Browse to http://JENKINS_CONTAINER_IP:8080 (in my case http://10.42.13.224:8080) and you will see Jenkins Dashboard. Before starting you must install Github Plugin and Maven following these steps:

Click Manage Jenkins menu option and then Manage Plugins Go to Available tab and search for Github plugin, named “Github Plugin”. Activate its checkbox Click Download now and install after restart button When the plugin is installed enable checkbox Restart Jenkins when installation is complete and no jobs are running, and then wait for Jenkins to be restarted When Jenkins is running again, go to Manage Jenkins and click Configure System In Maven section click Add Maven button, enter a name for the installation and choose last maven version. Click Save button to finish

When you are back in Dashboard click create new jobs link and follow these instructions:

Enter a job name, for example CI_Sample

Choose Maven project option and click OK

In Source Code Management section choose Git and enter this Repository URL: https://github.com/nixelsolutions/sample-war.git

In Build section enter the following maven goals and options. Replace TOMCAT_CONTAINER_IP with the IP assigned to your Tomcat container (10.42.236.18 in my case) and TOMCAT_ADMIN_PASSWORD with the password we saw before for admin user (6xc3gzOi4pMG in my case).

clean package tomcat7 : redeploy - DTOMCAT_HOST = TOMCAT_CONTAINER_IP - DTOMCAT_PORT = 8080 - DTOMCAT_USER = admin - DTOMCAT_PASS = TOMCAT_ADMIN_PASSWORD

I am setting this maven configuration:

clean package tomcat7 : redeploy - DTOMCAT_HOST = 10.42.236.18 - DTOMCAT_PORT = 8080 - DTOMCAT_USER = admin - DTOMCAT_PASS = 6 xc3gzOi4pMG

Save your job

Now you can click Build Now button to run your job. Open your execution (listed in Build History table) and then click Console Output option. If you go to the bottom you will see something like this: Testing the sample application Now browse to http://TOMCAT_CONTAINER_IP:8080/sample/ and you will see this page showing information about Tomcat server and your browser client.

Conclusion

In this post we have installed a basic Continuous Integration environment as an example to make your Docker containers reachable from your PC, your LAN, and even a mobile device or any system that can execute an OpenVPN client. This is possible thanks to Rancher Network, a great functionality that improves Docker networking by connecting your containers under the same network. What we actually did was to extend Rancher network using an OpenVPN link that is really easy to configure with Docker, and secure to use because all your traffic is being encrypted. This functionality can help many companies to better manage the way they give access to their containers from any unknown or uncontrolled network. Now you don’t need to think anymore about exposing or mapping ports, changing firewall rules, or taking care about what services you publish to the Internet. For more information on managing docker with Rancher, please join our next online meetup, where we’ll be demonstrating Rancher, Docker Compose, service discovery and many other capabilities. Manel Martinez is a Linux systems engineer with experience in the design and management of scalable, distributable and highly available open source web infrastructures based on products like KVM, Docker, Apache, Nginx, Tomcat, Jboss, RabbitMQ, HAProxy, MySQL and XtraDB. He lives in Spain, and you can find him on Twitter @manel_martinezg.