kubernetes-ansible

Install and configure a kubernetes cluster including network plugin.

Requirements

Tested on Debian Jessie and Ubuntu (14.10, 15.04, 15.10).

• The target servers must have access to the Internet in order to pull docker imaqes.
• The firewalls are not managed, you'll need to implement your own rules the way you used to.

Ansible v1.9.x

Components

• kubernetes v1.1.3
• etcd v2.2.2
• calicoctl v0.13.0
• flanneld v0.5.5
• docker v1.9.1

Quickstart

The following steps will quickly setup a kubernetes cluster with default configuration. These defaults are good for tests purposes.

Edit the inventory according to the number of servers

[downloader]
10.115.99.1

[kube-master]
10.115.99.31

[etcd]
10.115.99.31
10.115.99.32
10.115.99.33

[kube-node]
10.115.99.32
10.115.99.33

[k8s-cluster:children]
kube-node
kube-master

Run the playbook

ansible-playbook -i inventory/inventory.cfg cluster.yml -u root

You can jump directly to "Available apps, installation procedure"

Ansible

Download binaries

A role allows to download required binaries. They will be stored in a directory defined by the variable 'local_release_dir' (by default /tmp). Please ensure that you have enough disk space there (about 300M).

Note: Whenever you'll need to change the version of a software, you'll have to erase the content of this directory.

Variables

The main variables to change are located in the directory inventory/group_vars/all.yml.

Inventory

Below is an example of an inventory. Note : The bgp vars local_as and peers are not mandatory if the var 'peer_with_router' is set to false By default this variable is set to false and therefore all the nodes are configure in 'node-mesh' mode. In node-mesh mode the nodes peers with all the nodes in order to exchange routes.

[downloader]
10.99.0.26

[kube-master]
10.99.0.26
10.99.0.59

[etcd]
10.99.0.26
10.99.0.4
10.99.0.59

[kube-node]
10.99.0.59
10.99.0.4
10.99.0.5
10.99.0.36
10.99.0.37

[paris]
10.99.0.26
10.99.0.4 local_as=xxxxxxxx
10.99.0.5 local_as=xxxxxxxx

[usa]
10.99.0.59 local_as=xxxxxxxx
10.99.0.36 local_as=xxxxxxxx
10.99.0.37 local_as=xxxxxxxx

[k8s-cluster:children]
kube-node
kube-master

Playbook

---
- hosts: downloader
  sudo: no
  roles:
    - { role: download, tags: download }

- hosts: k8s-cluster
  roles:
    - { role: etcd, tags: etcd }
    - { role: docker, tags: docker }
    - { role: dnsmasq, tags: dnsmasq }
    - { role: network_plugin, tags: ['calico', 'flannel', 'network'] }

- hosts: kube-master
  roles:
    - { role: kubernetes/master, tags: master }

- hosts: kube-node
  roles:
    - { role: kubernetes/node, tags: node }

Run

It is possible to define variables for different environments. For instance, in order to deploy the cluster on 'dev' environment run the following command.

ansible-playbook -i inventory/dev/inventory.cfg cluster.yml -u root

Kubernetes

Multi master notes

• You can choose where to install the master components. If you want your master node to act both as master (api,scheduler,controller) and node (e.g. accept workloads, create pods ...), the server address has to be present on both groups 'kube-master' and 'kube-node'.

• Almost all kubernetes components are running into pods except kubelet. These pods are managed by kubelet which ensure they're always running

• For safety reasons, you should have at least two master nodes and 3 etcd servers

• Kube-proxy doesn't support multiple apiservers on startup (Issue 18174). An external loadbalancer needs to be configured. In order to do so, some variables have to be used 'loadbalancer_apiserver' and 'apiserver_loadbalancer_domain_name'

Network Overlay

You can choose between 2 network plugins. Only one must be chosen.

• flannel: gre/vxlan (layer 2) networking. (official docs)

• calico: bgp (layer 3) networking. (official docs)

The choice is defined with the variable 'kube_network_plugin'

Expose a service

There are several loadbalancing solutions. The one i found suitable for kubernetes are Vulcand and Haproxy

My cluster is working with haproxy and kubernetes services are configured with the loadbalancing type 'nodePort'. eg: each node opens the same tcp port and forwards the traffic to the target pod wherever it is located.

Then Haproxy can be configured to request kubernetes's api in order to loadbalance on the proper tcp port on the nodes.

Please refer to the proper kubernetes documentation on Services

Check cluster status

Kubernetes components

• Check the status of the processes

systemctl status kubelet

• Check the logs

journalctl -ae -u kubelet

• Check the NAT rules

iptables -nLv -t nat

For the master nodes you'll have to see the docker logs for the apiserver

docker logs [apiserver docker id]

Available apps, installation procedure

There are two ways of installing new apps

Ansible galaxy

Additionnal apps can be installed with ansible-galaxy.

ou'll need to edit the file 'requirements.yml' in order to chose needed apps. The list of available apps are available there

For instance it is strongly recommanded to install a dns server which resolves kubernetes service names. In order to use this role you'll need the following entries in the file 'requirements.yml' Please refer to the k8s-kubedns readme for additionnal info.

- src: https://github.com/ansibl8s/k8s-common.git
  path: roles/apps
  # version: v1.0

- src: https://github.com/ansibl8s/k8s-kubedns.git
  path: roles/apps
  # version: v1.0

Note: the role common is required by all the apps and provides the tasks and libraries needed.

And empty the apps directory

rm -rf roles/apps/*

Then download the roles with ansible-galaxy

ansible-galaxy install -r requirements.yml

Git submodules

Alternatively the roles can be installed as git submodules. That way is easier if you want to do some changes and commit them.

You can list available submodules with the following command:

grep path .gitmodules | sed 's/.*= //'

In order to install the dns addon you'll need to follow these steps

git submodule init roles/apps/k8s-common roles/apps/k8s-kubedns
git submodule update

Finally update the playbook apps.yml with the chosen roles, and run it

...
- hosts: kube-master
  roles:
    - { role: apps/k8s-kubedns, tags: ['kubedns', 'apps']  }
...

ansible-playbook -i environments/dev/inventory apps.yml -u root

Calico networking

Check if the calico-node container is running

docker ps | grep calico

The calicoctl command allows to check the status of the network workloads.

• Check the status of Calico nodes

calicoctl status

• Show the configured network subnet for containers

calicoctl pool show

• Show the workloads (ip addresses of containers and their located)

calicoctl endpoint show --detail

Flannel networking

Congrats ! now you can walk through kubernetes basics