Tuesday, November 3, 2015

Mesos/Kubernetes: How to install and run Kubernetes on Mesos with your local cluster?

First of all, let me share with you my test environment:
(1) CentOS 7.1.1503 (nodes = hdp1, hdp2 and hdp3)
(2) HDP 2.3.2 (re-using the installed Zookeeper)
(3) Docker v1.8.3
(4) golang 1.4.2
(5) etcd 2.1.1

The official documentation for Kubernetes-Mesos integration can be found here. It uses Google Compute Engine (GCE), but this blog entry will share about deploying Kubernetes-Mesos integration on a local cluster.

Ok, let's begin...


(1) A working local Mesos cluster
NOTE: To build one, please refer to this.

(2) Install Docker on ALL nodes.
(a) Make sure yum has access to the official Docker repository.
(b) Execute "yum install docker-engine"
(c) Enable docker.service with "systemctl enable docker.service"
(d) Start docker.service with "systemctl start docker.service"

(3) Install "golang" on the node which you wish to install and deploy Kubernetes-Mesos integration.
(a) Execute "yum install golang"

(4) Install "etcd" on a selected node (preferably on the node that host the Kubernetes-Mesos integration for testing purposes).
(a) Execute "yum install etcd"
(b) Amend file "/usr/lib/systemd/system/etcd.service" (see below):
ExecStart=/bin/bash -c "GOMAXPROCS=$(nproc) /usr/bin/etcd"
ExecStart=/bin/bash -c "GOMAXPROCS=$(nproc) /usr/bin/etcd --listen-client-urls --advertise-client-urls http://[node_ip]:4001"
[node_ip] = IP Address of the node (hostname -i)

(c) Reload systemctl daemon with "systemctl daemon-reload".
(d) Enable etcd.service with "systemctl enable etcd.service".
(e) Start etcd.service with "systemctl start etcd.service".


Build Kubernetes-Mesos

NOTE: Execute the following on the node selected to host the Kubernetes-Mesos integration.
cd [directory to install kubernetes-mesos]
git clone https://github.com/kubernetes/kubernetes
cd kubernetes


Export environment variables

(1) Export the following environment variables:

export KUBERNETES_MASTER_IP=$(hostname -i)
export MESOS_MASTER=[zk://.../mesos]
export PATH="[directory to install kubernetes-mesos]/_output/local/go/bin:$PATH"

[zk://.../mesos] = URL of the zookeeper nodes (Eg. zk://hdp1:2181,hdp2:2181,hdp3:2181/mesos)
[directory to install kubernetes-mesos] = Directory used to perform "git clone" (see "Build Kubernetes-Mesos" above).

(2) Amend .bash_profile to make the variables permanent.
(3) Remember to source the .bash_profile file after amendment (. ~/.bash_profile).


Configure and start Kubernetes-Mesos service

(1) Create a cloud config file mesos-cloud.conf in the current directory with the following contents:
$ cat <<EOF >mesos-cloud.conf
        mesos-master        = ${MESOS_MASTER}
If you have not set ${MESOS_MASTER}, it should be like (example) "zk://hdp1:2181,hdp2:2181,hdp3:2181/mesos".

(2) Create a script to start all the relevant components (API server, controller manager, and scheduler):

km apiserver \
  --address=${KUBERNETES_MASTER_IP} \
  --etcd-servers=http://${KUBERNETES_MASTER_IP}:4001 \
  --service-cluster-ip-range= \
  --port=8888 \
  --cloud-provider=mesos \
  --cloud-config=mesos-cloud.conf \
  --secure-port=0 \
  --v=1 >apiserver.log 2>&1 &

sleep 3

km controller-manager \
  --master=${KUBERNETES_MASTER_IP}:8888 \
  --cloud-provider=mesos \
  --cloud-config=./mesos-cloud.conf  \
  --v=1 >controller.log 2>&1 &

sleep 3

km scheduler \
  --address=${KUBERNETES_MASTER_IP} \
  --mesos-master=${MESOS_MASTER} \
  --etcd-servers=http://${KUBERNETES_MASTER_IP}:4001 \
  --mesos-user=root \
  --api-servers=${KUBERNETES_MASTER_IP}:8888 \
  --cluster-dns= \
  --cluster-domain=cluster.local \
  --contain-pod-resources=false \
  --v=2 >scheduler.log 2>&1 &

Since CentOS uses systemd, you will hit this issue. Hence, you need to add the "--contain-pod-resources=false" to the scheduler (in bold above).

(3) Give execute permission to the script (chmod 700 <script>).
(4) Execute the script.


Validate Kubernetes-Mesos services
$ kubectl get pods
# NOTE: Your service IPs will likely differ
$ kubectl get services
NAME             LABELS                                    SELECTOR   IP(S)          PORT(S)
k8sm-scheduler   component=scheduler,provider=k8sm         <none>   10251/TCP
kubernetes       component=apiserver,provider=kubernetes   <none>     443/TCP
(4) Lastly, look for Kubernetes in the Mesos web GUI by pointing your browser to http://[mesos-master-ip:port]. Go to the Frameworks tab, and look for an active framework named "Kubernetes".

Kubernetest framework is registered with Mesos

Let's spin up a pod

(1) Write a JSON pod description to a local file:
$ cat <<EOPOD >nginx.yaml
apiVersion: v1
kind: Pod
  name: nginx
  - name: nginx
    image: nginx
    - containerPort: 80
(2) Send the pod description to Kubernetes using the "kubectl" CLI:
$ kubectl create -f ./nginx.yaml
Submitted pod through kubectl
(3) Wait a minute or two while Docker downloads the image layers from the internet. We can use the kubectl interface to monitor the status of our pod:
$ kubectl get pods
nginx     1/1       Running   0          14s
(4) Verify that the pod task is running in the Mesos web GUI. Click on the Kubernetes framework. The next screen should show the running Mesos task that started the Kubernetes pod.
Mesos WebGUI shows active Kubernetes task

Mesos WebGUI shows that the Kubernetes task is RUNNING
Click through "Sandbox" link of the task to get to the "executor.log"

An example of "executor.log"

Connected to the node where the container is running

Getting Kubernetes to work on Mesos can be rather challenging at this point of time.

However, it is possible and hopefully, over time, Kubernetes-Mesos integration can work seamlessly.

Have fun!

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