Container Deployment andManagementwith kubernetes1 July 2015

Loh Siu YinTechnology Consultant, Beyond Broadcast LLP

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Kubernetes

A system to manage docker containers across a cluster of hosts.

See: kubernetes.io (http://kubernetes.io)

and github.com/GoogleCloudPlatform/kubernetes (https://github.com/GoogleCloudPlatform/kubernetes)

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Prerequisites

Docker (boot2docker, coreos, static binary)

Images (from hub.docker.com or build your own)

kubernetes

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Docker Essentials

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Docker Overview

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Build a base image

Dockerfile for gozmq: A standardized environment my golang and ZeroMQ programsto run in.

# Dockerfile for gozmqFROM ubuntu:14.04ADD libzmq.so.1 /usr/lib/CMD ["/bin/bash"]

Building the image:

#!/bin/sh# image_build.shPGM='gozmq'MAIN_VER=20150525#MAIN_VER=`date +%Y%m%d`SUB_VER=VER=${MAIN_VER}${SUB_VER}

docker build -t siuyin/${PGM}:${VER} .

Check with: docker images | grep gozmq

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Build application image: master-publisher

The publisher in a pub-sub system.

# Dockerfile for publisherFROM siuyin/gozmq:20150525ENV PULL_BIND_PORT='tcp://*:5123'ENV PUB_BIND_PORT='tcp://*:5124'ADD publisher /usr/bin/CMD ["/usr/bin/publisher"]

#!/bin/sh# image_build for publisherPGM='publisher'#MAIN_VER=`date +%Y%m%d`MAIN_VER=20150525SUB_VER=VER=${MAIN_VER}${SUB_VER}

docker build -t siuyin/${PGM}:${VER} .

Check with: docker images | grep publisher

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Publisher

Demo:

cd ~/prog/go_workspace/src/siuyin/zmqcomp/publisher (vim start.sh)

test_pusher, publisher then test_subscriber

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Nice: Fully functional but limited to running on the docker host

Note: localhost and port configuration via environment variables.

#!/bin/sh# test_pusher# local docker host#PUSH_CONNECT_HOST=localhost PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes cluster network 1#PUSH_CONNECT_HOST=172.17.0.17 PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes cluster network 2PUSH_CONNECT_HOST=10.0.0.50 PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes node local#PUSH_CONNECT_HOST=localhost PUSH_CONNECT_PORT=30516 go run main.go

Enter kubernetes

Brendan Burns of Google: "kubernetes -- ancient greek for pilot"

I am thinking: The Borg Cube: "resistance is futile ... you will be assimilated"

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Kubernetes

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Kubernetes Overview

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Kubernetes Survival Guide

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Resources

pod:

One or more closely coupled docker containers

replication controller (or rc):

Actively manages pods

service (or svc):

A stable end-point to connect to running pods

node (previously minion):

A host that runs pods.

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(Re)starting kubernetes

After a reboot, kubernetes containers from gcr.io/google ... will not be running.Restart them with this script:

docker ps -a| grep gcr.io/google | awk '{print $1}'|xargs docker start

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Kubernetes operations

get: retrieve summary status on a resource (pod, rc, svc, node)

describe: get more details on a resource (eg. describe svc master-publisher)

delete: deletes a resource

create: creates a resource

Demo: kubectl get nodes

kubernetes cluster api-controller runs on localhost:8080 (http://localhost:8080)

Possible to curl to localhost:8080 with the api:

curl -L http://localhost:8080/api/v1beta3/nodes

or with GET requests on your browser localhost:8080/api/v1beta3/nodes (http://localhost:8080

/api/v1beta3/nodes)

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Creating a ReplicationController which creates pods

Defined in a .json or .yaml file:

"containers": [{ "name": "publisher", "image": "siuyin/publisher:20150525", "imagePullPolicy": "IfNotPresent", "env": [{ "name": "PULL_BIND_PORT", "value": "5123" },{ "name": "PUB_BIND_PORT", "value": "5124" }], "ports": [{ "containerPort": 5123, "protocol": "TCP" }, { "containerPort": 5124, "protocol": "TCP" } ] }], "restartPolicy": "Always", "volumes": []

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publisher-controller.json

view ~/prog/go_workspace/src/siuyin/zmqcomp/publisher/publisher-controller.json

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Demo: Create a replication controller

Note: kubectl delete rc -l name=master-publisher before re-creating replicationcontroller.

Demo:

cd ~/prog/go_workspace/src/siuyin/zmqcomp/publisher

kubectl create -f publisher-controller.json

kubectl get rc

Same effect with: kubectl get replicationcontrollers

Online scaling:

kubectl scale --replicas=3 rc master-publisher

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Where is the pod?

Demo:

kubectl get pods

or better

kubectl get pods -l 'name=master-publisher'

Same as: kubectl get pods --selector='name=master-publisher'

Note the IP Address of this pod.

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Pod IP address

Double-check: docker ps | grep master-publisher

Also: docker inspect <container UUID> | grep IPAddress

But where is the IP address in the docker container?

The network configuration is held in the "pause" container.

Demo: master-publisher pod running in dedicated sub-net

cd ~/prog/go_workspace/src/siuyin/zmqcomp/publisher

copy pod IP address to clipboard

configure and start test_pusher

configure and start test_subscriber

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Scenario: Container or Pod failure

Suppose bad code or hardware causes the docker container or pod to fail.

Can kubernetes heal the system?

Demo: kill the docker container

docker ps | grep master-publisher

docker kill <container UUID>

Demo: delete the pod

kubectl get pod -l name=master-publisher

kubectl delete pod <pod-name>

or similarly:

kubectl delete pod -l name=master-publisher

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How to survive a pod failure

The failed pod was re-created by the replication controller:

kubectl get pod -l name=master-publisher

note the pod's IP address

cat ~/prog/go_workspace/src/siuyin/zmqcomp/publisher/test_pusher/start.sh

The IP address changed!

Kubernetes made no attempt to revive the failed pod. Instead it created a new one andgave it a new IP address.

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We need a stable IP address!

Enter: kubernetes service

"kind":"Service", "apiVersion":"v1beta3", "metadata":{ "name":"master-publisher", "labels":{ "name":"master-publisher" } }, "spec":{

view ~/prog/go_workspace/src/siuyin/zmqcomp/publisher/publisher-service.json

Note the NodePort type and port declarations.

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Inspecting the service

I've already created the service with (don't create it again):

kubectl create -f publisher-service.json

Check it with:

kubectl get service -l name=master-publisher

kubectl describe svc master-publisher

Demo: reconfigure to use service IP address:

reconfigure test_pusher

reconfigure test_subscriber

Demo: fail the pod again

kubectl delete pod -l name=master-publisher

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Making the service accessible from outside the cluster

Specify a publicIP in the service declaration and use it:

#!/bin/sh# test_pusher# local docker host#PUSH_CONNECT_HOST=localhost PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes cluster network 1#PUSH_CONNECT_HOST=172.17.0.17 PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes cluster network 2PUSH_CONNECT_HOST=10.0.0.50 PUSH_CONNECT_PORT=5123 go run main.go

# kubernetes node local#PUSH_CONNECT_HOST=localhost PUSH_CONNECT_PORT=30516 go run main.go

To define your own port map, refer to NODEPORT entries in:

iptables -t nat -S

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Slides Download

http://www.slideshare.net/siuyin/siuyin-dockerkubernetes

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Thank you

Loh Siu YinTechnology Consultant, Beyond Broadcast LLPsiuyin@beyondbroadcast.com (mailto:siuyin@beyondbroadcast.com)

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