In this tutorial we’re going to show you how to provision a Docker Warm cluster with Rancher and how to visualize and monitor the cluster with Weave Scope.

In order to install the Rancher server you'll need a Linux box with Docker 17.06 or later. Deploy Rancher server with this command:

docker run -dp 8080:8080 --name=rancher --restart=unless-stopped rancher/server

Once the container is up you can access the Rancher UI from your browser on port 8080. The first thing you should do is to setup authentication. Navigate to the Access control section, chose the local authority for the Rancher Management interface and create an admin user with a password.

In order to provision Docker Swarm with Rancher you have to create a new environment. In Rancher UI select Manage Environments from the dropdown of environments, click on Add Environment and select an environment template that has Swarm as the orchestration.

After the Swarm environment has been created, you can navigate to the environment by selecting the name of the environment in the environment’s dropdown. For Swarm to work correctly you'll have to create 3 hosts. From the Infrastructure dropdown select Hosts and click on Add Host.

When creating the hosts make sure they are in the same network and the host OS kernel has the IP_VS_NFCT module enabled. Using Ubuntu 16.04 LTS will the mainline kernel should work fine. You can check if the host OS is compatible with Docker Swarm by running the Moby check-config.sh script.

Once the hosts have been added, Rancher will automatically start the deployment of the infrastructure services including the Swarm components and the Portainer containers. You can see the progress of the deployment by accessing Infrastructure Hosts from the menu.

When the health checks of all hosts are passing you can access Portainer from the Swarm dropdown. In Portainer UI you can see the Swarm cluster members by selecting Swarm from the left side menu.

Now that you have a Docker Swarm cluster up and running you can start monitoring it with Weave Scope. You'll need a Weave Could service token, if you don't have a Weave token go to Weave Cloud and sign up for a Weave Cloud account.

In order to visualize the Swarm cluster with Weave Cloud you have to deploy the Weave Scope container on each Swarm node. Like the Rancher infrastructure services, Scope needs to run with privileged mode and because Swarm services don't support privileged mode you'll have to use a one-shot service that will provision each node with a Scope container.

In Rancher UI navigate to Swarm CLI and create the scope-launcher global service with the following command:

docker service create --name scope-launcher --mode global --detach \
    --restart-condition none \
    --mount type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock \
    weaveworks/scope-swarm-launcher \
    scope launch --service-token=<WEAVE-CLOUD-TOKEN>

In Rancher UI navigate to Infrastructure containers and look for weavescope, you should see 3 containers running, one on each host:

The launcher will install Scope on each server and will exit. Using --restart-condition none we instruct Docker Swarm not to restart the service after it exits.

With --mode global we make sure Scope will be automatically deployed on new servers as you add them to the swarm.

Once the Scope containers are running on all hosts you can login into Weave Cloud and inspect your cluster.

With Weave Cloud Scope you can see your Rancher hosts, Docker containers and services in real-time. You can view metrics, tags and metadata of the running processes, containers or hosts. It’s the idea tool to visualize your Docker Swarm clusters and troubleshoot problems that may arise. Scope offers remote access to the Swarm’s nods and containers making it easy to diagnose issues in real-time.