Container Orchestrator Smackdown @ContinousLifecycle

Run Docker & Kubernetes on Exoscale
https://github.com/exoscale/multi-master-kubernetes

How important is orchestration and what is it for?
● Might not need it for small apps
● No orchestration == manual orchestration
● Manually place containers, network, scale, check, update
● Microservices & Cloud Native Applications

Design principles for Cloud Native Applications:
● Design for Performance responsiveness, concurrency, efficiency
● Design for Automation automate dev & ops tasks
● Design for Resiliency fault-tolerance, self-healing
● Design for Elasticity automatic scaling
● Design for Delivery minimise cycle-time, automate deployment
● Design for Diagnosability cluster-wide logs, traces & metrics

Let’s buy some socks...

Microservice reference application
● Intended to help people getting started with Microservices
● Great for comparing frameworks, test driving new tools...
● Inspired by the "Pet Store" for Java Frameworks
... and “TodoMVC” for JavaScript
Implementations for 10+ Cloud/Container environments:
https://github.com/microservices-demo/microservices-demo/tree/master/deplo
y

Architecture

Comparing
Orchestrators

Comparing orchestrators
● All work and are improving rapidly
● Understand the differences
● Understand your requirements
● Please don't roll your own!

The players
● Kubernetes
● Mesos (different workloads)
● Docker Swarm Mode
● Plus others
○ Nomad, PaaSs...

Side note - the Borg/Omega papers
● Influential papers from Google
● Lessons learnt from 10 years with containers
● Google contributed cgroups to the Linux kernel, cgroups and linux
namespaces are the heart of containers

Docker Swarm Mode

Docker Swarm Mode
● New in Docker 1.12
● Docker Inc's official solution
● Part of core distribution
● Major improvement over TOS (“The Original Swarm”)

Core components
● Manager nodes
○ coordinate via Raft
○ no need for separate etcd/zookeeper
● Worker nodes

Usability
● Swarm extends concepts from single-node Docker to multi-node setups
● If you are up to date on standard Docker concepts, you’ll pick it up quickly
● Setting up a new Swarm is easy as pie

Easy to install
$ docker swarm init
Swarm initialized: current node (10vh26gyxppo6j2vyb8rcvjwj) is now a
manager.
To add a worker to this swarm, run the following command:
docker swarm join
--token SWMTKN-1-5td5x39z8jw...ccrjmkt1o8du3
172.17.9.102:2377
To add a manager to this swarm, run 'docker swarm join-token manager'
and follow the instructions.

Secure communication by default
● TLS set up using self-signed certs
● Certificates automatically rotated

Feature Set
● Services
● Networks
● Constraints and labels

Services
● Fixed number of containers are launched together and are kept running
● Two types of services: replicated or global
○ Replicated: Maintain a specified number of containers across the cluster
○ Global: Run one instance of a container on each swarm node

Networks
● Allows creating named overlay networks...
● … which are isolated, flat, encrypted virtual networks
across your Swarm nodes to launch your containers into

● Control which node a container can be scheduled on
● E.g.:
○ Only nodes labeled staging
○ Only nodes which have the image
○ Only the node running a given container (affinity rules)
Constraints and Filters

Other features
● Spread scheduling
○ chooses "least loaded" node
○ More options later
○ support for reserving &
limiting cpu/memory

Application definition
● Apps are defined in DAB can be deployed on a Swarm cluster
● Possible to scale individual containers defined in the DAB file (manual)
Testing Swarm Mode with Socks Shop:
https://raw.githubusercontent.com/microservices-demo/
microservices-demo/master/deploy/swarmkit/start-swarmkit-services.sh

Swarm Mode advantages
● Easy to install
● Secure by default
● “Bundled with Docker”

Swarm Mode disadvantages
● Very new
● Some Docker features unsupported (--privileged, --read-only, …)
● DAB still WIP

Kubernetes
often just “K8S”

Kubernetes
● Based on Google's experience running containers
● Many advanced features baked in:
○ Load-balancing
○ Secrets management
○ RBAC (Role Based Access Control)
○ …
● More opinionated

Core concepts
● Pods
● Labels
● Services
● Deployments
● ReplicaSets

Pods
● Groups of containers deployed and scheduled together
● Atomic unit of deployment
● Containers in a pod share IP address
● Single container pods are most common case
● Pods are ephemeral

Labels
● Key/Value pairs attached to objects (primarily pods)
○ e.g. version: dev, tier: frontend
● Label selectors then used to group objects
● Used for load-balancing etc.

Services
● Stable endpoints addressed by name
● Forward traffic to pods
● Pods are selected by labels
● Round-robin load-balancing
● Separates endpoint from implementation

Deployments & ReplicaSets
● ReplicaSets monitor status of Pods
○ start/stop pods as needed
● Deployments start/create ReplicaSets
● Rollout/Rollback & Updates

Usability
● Setting up a production grade Kubernetes-cluster from scratch requires
setting up etcd, networking plugins, DNS servers and certificate authorities.
○ Will change pretty soon with future versions of kubeadm
● Beyond initial setup, Kubernetes still has a steeper learning curve

Snap to install
$kubeadm init
<master/tokens> generated token: "f0c861.753c505740ecde4c"
<master/pki> created keys and certificates in "/etc/kubernetes/pki"
<util/kubeconfig> created "/etc/kubernetes/kubelet.conf"
<util/kubeconfig> created "/etc/kubernetes/admin.conf"
<master/apiclient> created API client configuration
<master/apiclient> created API client, waiting for the control plane to become ready
<master/apiclient> all control plane components are healthy after 61.346626 seconds
<master/apiclient> waiting for at least one node to register and become ready
<master/apiclient> first node is ready after 4.506807 seconds
<master/discovery> created essential addon: kube-discovery
<master/addons> created essential addon: kube-proxy
<master/addons> created essential addon: kube-dns
Kubernetes master initialised successfully!
You can connect any number of nodes by running:
$kubeadm join --token <token> <master-ip>

Application Definition
● A combination of Pods, Replication Controllers, Replica Sets, Services and
Deployments
● Each application tier is defined as a pod and can be scaled when managed
by a Deployment or ReplicationController/ReplicaSet.
The scaling can be manual or automated
● Auto-scaling using a simple number-of-pods target is defined declaratively
with the API exposed by ReplicationControllers or ReplicaSets
Testing Kubernetes with Sock Shop:
https://github.com/microservices-demo/microservices-demo/blob/master/dep
loy/kubernetes/complete-demo.yaml

Kubernetes Advantages
● Easy to install (with kubeadm)
○ Currently limited to a single master installation
○ Currently limited to a single etcd installation
● Advanced features baked-in
● Lots of momentum behind the community

Kubernetes disadvantages
● Harder to get started
● Extra concepts to learn

Conclusion
● Different options with different strengths
● In some ways surprisingly similar (k8s Deployment | Swarm service)
● Hard to predict a winner
● All are much better than rolling-your-own

Trainings: Docker, Kubernetes, Microservices,
Docker Security, Mesos… info@container-solutions.com

Container Orchestrator Smackdown @ContinousLifecycle

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